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Title: Agricultural zoology
Author: J. Ritzema Bos
Contributor: Eleanor Anne Ormerod
Translator: James Richard Ainsworth Davis
Release date: October 13, 2025 [eBook #77045]
Language: English
Original publication: London: Chapman & Hall, 1894
Credits: Richard Tonsing, Peter Becker, and the Online Distributed Proofreading Team at https://www.pgdp.net (This file was produced from images generously made available by The Internet Archive)
*** START OF THE PROJECT GUTENBERG EBOOK AGRICULTURAL ZOOLOGY ***
AGRICULTURAL ZOOLOGY
BY
DR. J. RITZEMA BOS,
LECTURER IN THE ROYAL AGRICULTURAL COLLEGE, WAGENINGEN, HOLLAND.
WITH AN INTRODUCTION BY
ELEANOR A. ORMEROD, F.R.MET.S., F.R.M.S., ETC.,
FORMERLY HON. CONSULTING ENTOMOLOGIST TO THE ROYAL AGRICULTURAL SOCIETY
OF ENGLAND.
TRANSLATED BY
J. R. AINSWORTH DAVIS, B.A. (TRIN. COLL. CAMB.), F.C.P.,
PROFESSOR IN THE UNIVERSITY OF WALES, AND PROFESSOR OF BIOLOGY AND
GEOLOGY IN THE SCIENTIFIC AND AGRICULTURAL DEPARTMENTS OF THE UNIVERSITY
COLLEGE OF WALES.
WITH 149 ILLUSTRATIONS.
LONDON: CHAPMAN & HALL, LD.
1894
AUTHOR’S PREFACE.
The present volume of the Thaer Library was undertaken with the
intention of providing agricultural colleges with a condensed review of
the entire animal kingdom, but treating in greater detail the animals
harmful or helpful to agriculture. I have, however, omitted all
reference to the domesticated farm animals, as in all such institutions
these are treated of, not by the zoologist, but by the lecturer on
stock-breeding. Although the book is not allowed to exceed a certain
size, I have taken great pains to make it intelligible, and venture to
hope that it may be found suitable for the _private use of the practical
farmer_. To the farmer who wishes more exhaustive information, and
desires a reference book on the animal foes of agriculture,
stock-breeding, horticulture, fruit-tree culture, and forestry, I
venture to point out my larger work, _Animal Foes and Friends_,[1]
brought out last year by the publisher of this book.
Footnote 1:
Tierische Schädlinge und Nützlinge für Ackerbau, Viehzucht, Wald- und
Gartenbau. Lebensformen, Vorkommen, Einfluss und die Massregeln zu
Vertilgung und Schutz. Praktisches Handbuch v. _Dr. J. Ritzema Bos_,
Docent an der landwirtschaftl. Lehranstalt in Wageningen. Mit 477
eingedruckten Abbildungen. Preis 18 m., geb. 20 m. Verlag von Paul
Parey, 10 Hedemannstrasse, Berlin, S.W.
It is hoped that the present volume may be found serviceable, both in
the teaching of agricultural institutions, and to the practical farmer.
DR. J. RITZEMA BOS.
WAGENINGEN,
_February, 1892_.
TRANSLATOR’S PREFACE.
Agricultural education is making such rapid strides in this country,
that no apology is needed for translating a book which appears to fill a
gap, especially as it is written by a well-known authority. Dr. Ritzema
Bos has kindly allowed certain small alterations to be made which adapt
the work to the requirements of British agriculture. Additions are
indicated by square brackets, and small print employed in the case of
some non-British animals. A few forms have been omitted for similar
reasons. Constant reference has been made to the published works of Miss
E. A. Ormerod, who has added to my obligation by writing an
Introduction, and I also wish to acknowledge my indebtedness to Mr. J.
H. Salter, B.Sc., and Mr. J. Dawson Roberts, M.R.C.V.S., for kind help
given by them.
J. R. AINSWORTH DAVIS.
ABERYSTWYTH,
_May, 1894_
INTRODUCTION.
By request of Professor Ainsworth Davis, the skilled translator of this
“handy-book” on “Agricultural Zoology,” I add some words of
introduction; and I have especial pleasure in so doing: not that any
observations of mine can add value to the work of the well-known author,
but because, having myself had the advantage for many years of
colleagueship, and important help in my own work from the assistance of
Dr. Ritzema Bos, I am well acquainted both with his extensive knowledge
and also his scrupulous care in observation, and I believe that this
abstract of his larger work, now given in a form in which it is
available for general use, will meet a great need.
We have long wanted a book, plain in wording, and of moderate size,
dealing with the wild animals or animal infestations generally which
occur in connection with farm life—a manual, in fact, which, whilst
suitable for the use of agricultural students and teachers, should at
the same time not be too technically scientific to be intelligible to
practical farmers or to general readers.
In the pages of the present volume a very serviceable amount of
information will be found to be embodied. So far as can be arranged in
the limited space the chief characteristics of the main divisions of the
animal kingdom are given, from the _Vertebrata_—including descriptions
of some of our most notable forms of what may be popularly described as
beasts, birds, and reptiles,—to the _Arthropoda_, including information
on a most serviceable amount of insect infestation; also regarding
Mites, Ticks, etc. These are followed by the _Vermes_, including, among
other families of the _Nematoda_, the eelworms which cause so much
injury to crop growth; and these are followed by the intestinal
tapeworms and the fluke.
The fourth sub-kingdom, that of _Mollusca_, includes, besides snails and
slugs, various kinds of shell-fish; and the lower sub-kingdoms—including
_Echinodermata_, which may be typified by starfishes and sea urchins,
the _Cœlenterata_, or Zoophytes, and the _Protozoa_—will be found to be
just entered on sufficiently to show their place in the scale.
The clear descriptions, made still more instructive by the numerous and
good figures, will speak for themselves to all readers; but I should
like to add a few lines to point out the serviceableness of a handbook
in which the reader may turn at pleasure to the history of any common
farm animal—as a weasel or a vole, a wood-pigeon or a pheasant, a
blindworm or a common frog. And, in regard to the insect infestations,
to which it will be seen more than a hundred pages of the book are
devoted, I can bear witness to the great amount of valuable information
which I constantly derive myself from the study of the writings of Dr.
Ritzema Bos on this subject; and I trust this little manual of
“Agricultural Zoology” may take the place in our farm and school
libraries which I believe it to be excellently fitted to fill.
ELEANOR A. ORMEROD,
_Late Consulting Entomologist of the Royal
Agricultural Society of England_.
TORRINGTON HOUSE, ST. ALBAN’S,
_May 24, 1894_.
CONTENTS.
PAGE
INTRODUCTION—
I. Subdivision of the Animal Kingdom 1
II. Review of the Structure and Vital Phenomena of Animals 3–16
=First Sub-Kingdom: VERTEBRATA (Backboned Animals)= 16–82
CLASS I: MAMMALIA (Sucklers) 21–48
ORDER: Carnivora (Beasts of Prey) 24–30
Family: Felidæ (Cat Family) 24–25
Family: Canidæ (Dog Family) 25–26
(Wolf, p. 25; Fox, p. 26.)
Family: Mustelidæ (Weasel Family) 26–30
(Martens and Polecat, p. 26; Ferret, p. 27; Stoat and
Weasel, p. 28; Mink, Otter, and Badger, p. 29.)
ORDER: Insectivora (Insect-eating Mammals) 30–33
(Shrews, pp. 30, 31; Mole, pp. 31–33; Hedgehog, p. 33.)
ORDER: Cheiroptera (Bats) 33–35
ORDER: Rodentia (Gnawing Mammals) 35–43
Family: Leporidæ (Hares and Rabbits) 36–38
(Hare and Rabbit, p. 37.)
Family: Muridæ (Mouse Family) 38–41
(Hamster, Black Rat, and Brown Rat, p. 39; Common Mouse,
Long-tailed Field Mouse, and Harvest Mouse, p. 40; Corn
Mouse, p. 41.)
Family: Arvicolidæ (Vole Family) 41–43
(Bank Vole and Water Vole, p. 42; Field Vole, pp. 42, 43;
Southern Field Vole, p. 43.)
ORDER: Ruminantia (Cud-chewing Mammals) 44–47
Family: Cervidæ (Deer Family) 45–47
(Red Deer, p. 46; Roebuck and Fallow Deer, p. 47.)
ORDER: Multungula or Pachydermata (Many-hoofed or
Thick-skinned Mammals) 48
(Wild Boar, p. 48.)
ORDER: Solidungula (Single-hoofed Mammals) 48
CLASS II: AVES (Birds) 49–74
ORDER: Raptores (Birds of Prey) 53–55
ORDER: Scansores (Climbing Birds) 55–56
(Cuckoo, pp. 55, 56.)
ORDER: Passeres (Perching Birds) 57–65
Group: Hirundinidæ (Swallows) 57–58
(Swallows and Martins, p. 57; Swift and Goatsucker, p.
58.)
Group: Magnirostres (Large-beaked Perchers) 58–61
(Jackdaw, Crows, Rook, and Raven, pp. 59–61; Magpie and
Jay, p. 61.)
Group: Conirostres (Conical-beaked Perchers) 61–64
(Titmice, Larks, and Buntings, pp. 61, 62; Finches, p.
62; Sparrows, pp. 62, 63; Linnet, p. 63; Chaffinch, pp.
63, 64.)
Group: Subulirostres (Awl-beaked Perchers) 64–65
(Wagtails, Pipits, and Hedge “Sparrow,” p. 64; Warblers,
pp. 64, 65; Thrush-like birds, p. 65.)
ORDER: Gyrantes (Doves) 65–67
(Wood Pigeon, pp. 66, 67; Turtle Dove and Rock Pigeon, p.
67.)
ORDER: Rasores (Poultry) 67–68
(Pheasant, p. 68.)
ORDER: Grallatores (Wading-Birds) 68–70
ORDER: Natatores (Swimming-Birds) 70–74
Family: Lamellirostra (Ducks) 71–73
Family: Longipennes (Gulls) 73–74
CLASS III.: REPTILIA (Reptiles) 74–79
CLASS IV.: AMPHIBIA (Amphibians) 79–81
CLASS V.: PISCES (Fishes) 81–82
=Second Sub-Kingdom: ARTHROPODA (Jointed-limbed Animals)= 82–206
CLASS I.: INSECTA (Insects) 85–194
ORDER I.: Coleoptera (Beetles) 94–118
Family: Carabidæ (Ground Beetles) 94–96
(Corn Ground Beetle, pp. 95, 96.)
Family: Staphylinidæ (Rove Beetles) 96–97
Family: Silphidæ (Burying Beetles) 97
(Black Burying Beetle, and Beet Carrion Beetle, p. 97.)
Family: Nitidulidæ (Shine Beetles) 97–98
(Turnip-flower Beetle, pp. 97, 98.)
Family: Cryptophagidæ (Secret-eating Beetles) 98–99
(Beet Beetle, pp. 98, 99.)
Family: Lamellicornia (Chafers) 99–102
(Cockchafer, pp. 100, 101; Buckwheat Beetle, p. 101; Rye
and Garden Chafers, p. 102.)
Family: Elateridæ (Click Beetles) 102–105
(“Wireworms,” pp. 103–105.)
Family: Curculionidæ (Weevils) 105–110
(Seed Beetles, pp. 106, 107; Pea Weevil, pp. 107, 108;
Mouse-tooth Weevils, p. 108; Gall Weevils, pp.
108–110.)
Family: Chrysomelidæ (Leaf Beetles) 110–117
(Colorado Beetle, pp. 111–113; Tortoise Beetles, pp. 113,
114; Flea Beetles, 114–117.)
Family: Coccinellidæ (Lady Birds) 117–118
ORDER II.: Orthoptera (Straight-winged Insects) 118–121
(Migratory Grasshopper, pp. 119, 120; Mole Cricket, pp.
120, 121.)
ORDER III.: Neuroptera (Net-winged Insects) 121–123
(Dragon Flies, p. 122; Lace Flies, pp. 122, 123; Scorpion
Flies, p. 123.)
ORDER IV.: Hymenoptera (Membranous-winged Insects) 123–136
Family: Apidæ (Bees) 125–126
Family: Vespidæ (Wasps) 126–128
Family: Fossores (Digging Wasps) 128–129
Family: Formicidæ (Ants) 129–132
Family: Ichneumonidæ (Ichneumon Flies) 132–134
Family: Tenthredinidæ (Saw-flies) 134–136
(Turnip Saw-fly, pp. 134–136.)
ORDER V.: Lepidoptera (Butterflies and Moths) 136–159
Family: Diurna (Butterflies) 137–142
(Whites, pp. 138–142.)
Family: Noctuidæ (Owlet Moths) 142–152
(Surface Caterpillars, p. 143; Dart or Turnip Moth, pp.
143–145; Cabbage Moth, pp. 145–147; Lettuce and Pea
Moths, p. 147; Grass-root Moth, p. 148; Couch-grass
Moth, pp. 148, 149; Wheat-haulm Moth, p. 149; Grass
Moth, pp. 149, 150; Darnel Moth, p. 150; Silver Y Moth,
pp. 151, 152.)
Family: Pyralidæ (Snout Moths) 152–155
Family: Tortricidæ (Leaf-rollers) 155–157
(Fawn-coloured Pea Moth, p. 156; Crescent Pea Moth, pp.
156, 157.)
Family: Tineidæ (Leaf-miners) 157–159
(Carrot Moth, pp. 157, 158; Diamond-back Moth, pp. 158,
159.)
ORDER VI.: Hemiptera (Half-winged Insects) 159–163
Family: Aphidæ (Plant Lice) 159–163
ORDER VII.: Physopoda (Bladder-footed Insects) 163–164
(Thrips, pp. 163, 164.)
ORDER VIII.: Diptera (Flies) 164–193
Family: Culicinæ (Gnats) 164–165
Family: Gallicolæ (Gall Gnats) 165–170
(Hessian Fly, pp. 166–168; Scarlet Wheat Midge, pp. 168,
169; Wheat Midge, 169, 170.)
Family: Rostratæ (Crane Flies) 170–172
Family: Muscæformes (Gnat Flies) 173–174
(Sand Flies, pp. 173, 174.)
Family: Tabanidæ (Gad Flies) 174
Family: Muscidæ (True Flies) 175–184
(Caterpillar and Flesh Flies, p. 175; Common Flies, p.
175; Flower Flies, pp. 176, 177; Cheese-fly, p. 178;
Ribbon-footed Corn Fly, pp. 178–182; Frit Fly, pp.
182–184.)
Family: Syrphidæ (Hover Flies) 185
Family: Stomoxydæ (Stable Flies) 185–186
Family: Œstridæ (Bot Flies) 186–192
(Ox Warble-fly, pp. 186–188; Sheep Bot Fly, pp. 188–190;
Horse Bot, etc., pp. 190–192.)
Family: Pupipara (Louse Flies) 192–193
ORDER IX.: Aphaniptera (Fleas) 193
ORDER X.: Parasita (Lice) 193–194
CLASS II.: MYRIOPODA (Centipedes and Millipedes) 195
CLASS III.: ARACHNOIDEA (Scorpions, Spiders, Mites) 195–205
ORDER: Acaridea (Mites) 196–202
Family: Acaridæ (True Mites) 196–202
(Itch or Mange Mites, pp. 196–202.)
Family: Ixodidæ (Ticks) 202–204
Family: Gamasidæ (Beetle Mites) 204
(Fowl Mite, p. 204.)
Family: Trombidiidæ 205
(Plant Mite or “Red Spider,” p. 205.)
CLASS IV.: CRUSTACEA (Crustaceans) 206
=Third Sub-Kingdom: VERMES (Worms)= 206–245
CLASS: ANNELIDA (Segmented Worms) 207–209
(Earthworms, pp. 207–209.)
CLASS: NEMATELMINTHES (Round Worms) 209–231
ORDER: Nematoda (Thread Worms) 210–231
Family: Strongylidæ (Palisade Worms) 212–215
Family: Trichotrachelidæ (Whip Worms) 215–218
(Trichina, pp. 216–218.)
Family: Filaridæ (Slender Thread Worms) 218
Family: Ascaridæ (Round Worms) 218–219
Family: Anguillulidæ (Eelworms) 219–231
(Stem Eelworm, pp. 220–224; Wheat Eelworm, pp. 224–227;
Beet Eelworm, pp. 227–230; Root-knot Eelworm, p. 231.)
CLASS: PLATYHELMIA (Flat Worms) 231–245
ORDER: Cestoda (Tapeworms) 231–240
ORDER: Trematoda (Flukes) 240–245
=Fourth Sub-Kingdom: MOLLUSCA (Mollusca)= 245–251
CLASS: CEPHALOPODA (Cuttlefishes) 247
CLASS: GASTROPODA (Snails and Slugs) 247–251
(Grey Field Slug, pp. 249–251.)
CLASS: LAMELLIBRANCHIATA (Bivalve Molluscs) 251
=Fifth Sub-Kingdom: ECHINODERMATA (Hedgehog-skinned Animals)= 252–253
=Sixth Sub-Kingdom: CŒLENTERATA (Zoophytes)= 253–255
=Seventh Sub-Kingdom: PROTOZOA (One-celled Animals)= 255–256
ILLUSTRATIONS.
FIG. PAGE
1. Schematic Longitudinal Section of the Human Body 4
2. Human Skeleton 7
3. Skeleton of an Ox 9
4. Bending of the Arm by Contraction of the Biceps Muscle 10
5. Diagram to explain the Action of the Motor and Sensory Nerves 11
6. Diagram of the Course of the Circulation 13
7. Life History of the Small-winged Gall-fly (_Andricus
terminalis_) 15
8. Diagram of a Fish’s Heart 18
9. Diagram of a Mammal’s Heart 20
10. Diagram of a Reptile’s Heart 20
11. Diagram of a Frog’s Heart 21
12. Vertical Section of a Human Grinding Tooth 22
13. Crown of an Ox’s Grinder 22
14. Skull of Domestic Cat 25
15. Pine Marten (_Mustela martes_) 27
16. Skull of Mole 30
17. Common Shrew (_Sorex vulgaris_) 31
18. Skeleton of Bat 34
19. Skull of Squirrel 35
20. Abnormal Tooth in Hare 37
21. Hamster (_Cricetus frumentarius_) 38
22. Long-tailed Field Mouse (_Mus sylvaticus_) 40
23. Upper Back Teeth of Brown Rat 41
24. Upper Back Teeth of Water Vole 41
25. Southern Field Vole (_Arvicola arvalis_) 43
26. Skull of Sheep 44
27. Development of Roebuck Antlers 45
28. Wing of Buzzard 50
29. Section through Bird’s Egg 51
30. Eagle Owl (_Otus maximus_) 52
31. Head and Foot of Falcon 53
32. Golden Eagle (_Aquila chrysaëtus_) 54
33. Barn Owl (_Strix flammea_) 55
34. Cuckoo (_Cuculus canorus_) 56
35. Goatsucker (_Caprimulgus europæus_) 58
36. Head of Rook (_Corvus frugilegus_) 60
37. Head of Bullfinch (_Pyrrhula vulgaris_) 62
38. Nightingale (_Daulias luscinia_) 65
39. Wood Pigeon (_Columba palumbus_) 66
40. Capercailzie (_Tetrao urogallus_) 68
41. Pheasant (_Phasianus colchicus_) 69
42. Woodcock (_Scolopax rusticola_) 70
43. Crested and Little Grebes (_Podiceps cristatus and minor_) 71
44. Grey Goose (_Anser cinereus_) 72
45. Herring Gull (_Larus argentatus_) 74
46. Common Lizard (_Lacerta agilis_) 75
47. Adder (_Pelias berus_) 76
48. Grass Snake (_Tropidonotus natrix_) 77
49. Blindworm (_Anguis fragilis_) 78
50. Great Crested Newt (_Triton cristatus_) 79
51. Common Frog (_Rana temporaria_) 80
52. Natterjack (_Bufo calamita_) 81
53. The Perch (_Perca fluviatilis_) 82
54. Wood-borer (_Sirex_) 83
55. Centipede (_Scolopendra morsitans_) 84
56. Ground Beetle, showing Nervous System 84
57. Disarticulated Grasshopper 85
58. Head and Mouth-parts of a Ground Beetle 87
59. Leg of Ground Beetle 88
60. Stages of Silkworm Moth (_Bombyx mori_) 88
61. Stages of Hornet (_Vespa crabro_) 89
62. Migratory Grasshopper (_Acrydium migratorium_) 90
63. Looper Caterpillar 90
64. False Caterpillar 90
65. Stages of Cockchafer (_Melolontha vulgaris_) 91
66. Larva of a Weevil 92
67. Stages of Aphis-eating Fly (_Syrphus pyrasti_) 92
68. A Ground Beetle (_Carabus auronitens_) 95
69. Corn Ground Beetle (_Zabrus gibbus_) and larva 95
70. A Rove Beetle (_Staphylinus erythropterus_) 96
71. Black Burying Beetle (_Silpha atrata_) and larva 96
72. Antennæ of Cockchafer 99
73. Abdomens of Common and Horse-chestnut Cockchafers 100
74. Skipjack (_Agriotes lineatus_) 102
75. Skipjack about to spring 103
76. Grain-plants sown deep and shallow, to show Wireworm attack 104
77. Bean Beetle (_Bruchus rufimanus_) 106
78. Pea Weevil (_Sitones lineatus_) 107
79. Mouse-tooth Weevil (_Baridius chloris_) and larva 108
80. Turnip Gall Weevil (_Ceutorhynchus sulcicollis_) 109
81. Colorado Beetle (_Chrysomela decemlineata_) 111
82. Stages of Colorado Beetle 112
83. Cloudy Tortoise Beetle (_Cassida nebulosa_) 113
84. Rape Flea Beetle (_Psylliodes chrysocephalus_) 114
85. Stages of Seven-spotted Lady-bird (_Coccinella
septempunctata_) 118
86. Stages of Common Lace Fly (_Chrysopa vulgaris_) 122
87. Head of Honey Bee (_Apis mellifica_) 124
88. Common Wasp (_Vespa vulgaris_) and nest 127
89. Common Sand Wasp (_Ammophila sabulosa_) 129
90. Stages of Yellow-legged Ichneumon Fly (_Microgaster
glomeratus_) 133
91. Turnip Saw-fly (_Athalia spinarum_) and caterpillars 135
92. Head of Butterfly 136
93. Scales from Butterfly’s Wing 136
94. Stages of Peacock Butterfly (_Vanessa io_) 138
95. Stages of Cabbage White (_Pieris brassicæ_) 139
96. Garden White (_Pieris rapæ_), male 141
97. Garden White, female and caterpillar 141
98. Green-veined White (_Pieris napi_) 142
99. Dart or Turnip Moth (_Agrotis segetum_) and caterpillar 143
100. Stages of Cabbage Moth (_Mamestra brassicæ_) 146
101. Grass Moth (_Charæas Graminis_) and caterpillar 150
102. Stages of Silver Y Moth (_Plusia gamma_) 151
103. Hop Snout Moth (_Hypena rostralis_) 153
104. Mother-of-Pearl Moth (_Botys margaritalis_) and larva 155
105. Fawn-coloured Pea Moth (_Grapholitha nebritana_) 156
106. Larch Moth (_Coleophora laricella_) 157
107. Wings of a Bug 159
108. Bean Aphis (_Aphis papaveris_) 160
109. Corn Thrips (_Thrips cerealium_) 163
110. Wheat Midge (_Cecidomyia tritici_) 165
111. Barley attacked by Hessian Fly 167
112. Larvæ of Wheat Midge (_Cecidomyia tritici_) 169
113. Stages of Daddy Longlegs (_Tipula oleracea_) 171
114. Rain Breeze Fly (_Hæmatopota pluvialis_) 174
115. Caterpillar Fly (_Tachina fera_) 175
116. Turnip infested by Cabbage Fly (_Anthomyia brassicæ_) 177
117. Ribbon-footed Corn Fly (_Chlorops tæniopus_) 179
118. Stages of ditto 181
119. Wheat Plant distorted by winter generation of ditto 181
120. Stages, etc., of Frit Fly (_Oscinis frit_) 183
121. Stages of Horse Bot Fly (_Gastrus equi_) 190
122. Horse Louse (_Hæmatopinus macrocephalus_) 194
123. Common Snake Millipede (_Julus terrestris_) 195
124. A Spider (_Salticus scenicus_) 196
125. Mange Mite of the Pig (_Sarcoptes scabiei, var. suis_) 197
126. Ditto 198
127. The Dog Tick (_Ixodes ricinus_) 203
128. Diagrammatic transverse section through a Thread Worm 210
129. Tail of male _Strongylus armatus_ 213
130. Encapsuled Muscle Trichinæ in flesh 217
131. Male Intestinal Trichina 217
132. Rye Plant in the later stage of the Eelworm Disease 222
133. Ear Cockles of Wheat 225
134. Stages of Beet Eelworm (_Heterodera Schachtii_) 226
135. _Tænia saginata_ 232
136. Common Tapeworm (_Tænia officinalis_) 234
137. Tapeworm Larva (_Tænia solium_) 234
138. Types of Bladder-worm 235
139. Measle of _Tænia solium_ 235
140. Measles in Pork 236
141. Liver Fluke (_Distoma hepaticum_) 241
142. Life History of Liver Fluke 242
143. Diagrams of Molluscs 246
144. Grey Field Slug (_Limax agrestis_) 249
145. Common Starfish (_Asterias rubens_) 252
146. Freshwater Polype (_Hydra_) 254
147. A Jellyfish (_Pelagia noctiluca_) 254
148. A Sea Anemone (_Sagartia nivea_) 254
149. Proteus Animalcule (_Amœba_) 255
ZOOLOGY.
INTRODUCTION.
I. Subdivision of the Animal Kingdom.
There are animals so like one another that they are given the same name.
Such animals are ranked in the same _species_. Animals which differ so
much that they have to be referred to different species, but which
notwithstanding agree in the majority of their characters, especially
the most important ones, are placed in the same _genus_. Hare and
rabbit, or horse and donkey, are reckoned as different species of the
same genus. Genera resembling one another are united into a _family_;
thus, the pine marten and the beech or stone marten both belong to the
_Marten genus_ (Martes), while the weasel and stoat are different
species of the _Weasel genus_ (Mustela); but these two genera are so
similar that they are both placed in the same family, _i.e._ the _Weasel
family_ (Mustelidæ). Nearly related families together build up an
_order_. Thus, the Weasel family, Dog family, Cat family, etc.,
collectively constitute the _order of Carnivora_, characterized,
speaking generally, by the same kind of teeth, claws, habits, and food.
Several related orders are united into a _class_. Thus, for example,
carnivorous animals (Carnivora), ruminating animals (Ruminantia),
gnawing animals (Rodentia), etc., constitute different orders of the
_class of Sucklers_ (Mammalia); while birds of prey (Raptores), pigeons
(Gyrantes), and poultry (Rasores), are included in a second class, that
of _Birds_ (Aves). But both Birds and Mammals have a skeleton, of which
the chief support is the backbone; on this account they are placed in a
larger subdivision, the _sub-kingdom_ of Backboned animals (Vertebrata);
while snails are grouped under the sub-kingdom of _Molluscs_, millipedes
and centipedes under that of _Jointed-limbed animals_ (Arthropods).
In this way the animal kingdom is divided into _sub-kingdoms_, the
sub-kingdoms into _classes_, the classes into _orders_, the orders into
_families_, the families into _genera_, and the genera into _species_.
Animals of the same species which differ from one another in more or
less constant characters, belong to different _races_ (domestic or
geographical races).
There are many species of animals the external features of which are
well known to ordinary folk, and which therefore possess a definite
English name, but a much larger number, of the smaller forms especially,
have no English name. It is, therefore, necessary to devise new names
for these species. The English names, however, are liable to cause great
confusion, since in different districts the same name is often applied
to widely different animals. Besides this, distinct names have usually
been given to successive stages in the life history of the same form:
“wireworms,” for example, are the young state of the “click beetle.”
By using the scientific method of naming invented by Linnæus, confusion
is made impossible. The Latin names of this naturalist have the great
advantage that they not only give a perfectly distinct name to any
particular species, but also at the same time show the genus to which it
belongs. Each kind of animal possesses, in fact, two names; just in the
same way as every person possesses at least two names, a Christian name
and a surname. The generic name comes first, and is, of course, common
to all animals of the same genus. The second name is the specific one,
and belongs exclusively to animals of the same species. The hare and
rabbit, for example, are both included in the genus _Lepus_. The Latin
name of the first is _Lepus timidus_; that of the second, _Lepus
cuniculus_. Horse = _Equus caballus_; ass = _Equus asinus_.
II. Review of the Structure and Vital Phenomena of Animals.
I select as a point of departure the human body, and the bodies of
domestic animals, because my readers are best acquainted with these.
The limbs consist, beginning on the outside, of skin, flesh, and bone.
The same parts can also be distinguished in the head, neck, and trunk;
but in these divisions of the body they enclose a cavity, the
_body-cavity_, which, again, contains various parts (“organs”), which
are not everywhere attached to the body-wall. Fig. 1 represents a
longitudinal section through the body. The skin is represented by a
line, flesh and internal lining are shaded, while the bones are black.
These parts form together the _body-wall_. In front the body-wall
encloses a cavity, the body-cavity (_Kh._), which in Mammals is divided
into two sections (thoracic cavity, _Bz.h_, and abdominal cavity,
_B.h._) by the _midriff_ (diaphragm). In the thoracic cavity are found
the lungs and heart (_H_), also most of the gullet or upper part of the
gut; the abdominal cavity contains the remainder of the often
much-coiled gut, which in one place widens into the stomach (_M_), also
the kidneys, spleen, and parts connected with the gut (_e.g._ the
liver). The cavities are bounded behind by the backbone (vertebral
column), which is made up of many flattened vertebræ. The uppermost
vertebra supports the skull, which encloses a _cranial cavity_
(_Sch.h._) continuous with a _vertebral canal_ bounded by the vertebræ.
Cranial cavity and vertebral canal form together a second body-space, in
which are contained the brain and spinal cord.
[Illustration:
FIG. 1.—Schematic Longitudinal Section of the Human Body.
]
We will now consider the individual parts of the body, beginning with
the _skeleton_. The axis of the skeleton is formed by the vertebral
column (spine), which is composed of flat bones, the _vertebræ_. A
vertebra usually consists of (1) the body, which occupies the front; (2)
the arch, which possesses several projections or processes (neural
spine, transverse processes, articular processes) and encloses the
vertebral canal (_W.h._). All mammals have seven neck or cervical
_vertebræ_ (Fig. 2, 1); while the number of the remaining vertebræ
varies according to the species. The cervical vertebræ, which support
the head, are followed by the dorsal or _thoracic vertebræ_ (12 in man,
Fig. 2, 2), and these by the strong loin or _lumbar vertebræ_ (5 in man,
Fig. 2, 3). Cervical, thoracic, and lumbar vertebræ are movable, but, in
man, the last-named are followed by five vertebræ immovably united
together to make up the _sacrum_, and these again by tail- or _caudal
vertebræ_. Man has four such vertebræ, all poorly developed, and fused
with one another (Fig. 2, 5); but in many animals there are a large
number, movably united to make up a tail.
The ribs, which in mammals bound the chest, are jointed to the thoracic
vertebræ. Man has 12 pairs of ribs; each rib consists of a bony part
behind and a gristly (cartilaginous) part in front. The so-called true
ribs (Fig. 2, 14) [the upper pairs] are movably united with the
breast-bone, but this is not the case with the false ribs (Fig. 2, 15).
In the head we distinguish the brain-case or _cranium_, and the skeleton
of the _face_. The first contains the cranial cavity in which the brain
is enclosed. We distinguish—2 frontal bones (fused together in man, Fig.
2, 6); 2 parietal bones (7); 2 temporal bones (8); an occipital bone (9)
composed of several pieces fused together, perforated by the foramen
magnum [where brain and spinal cord unite], and bearing two elevations
or condyles [for effecting union with the backbone]; and the sphenoid
and ethmoid bones which make up the base of the cranium. The facial
skeleton consists of the framework of the jaws and palate, and, together
with some of the cranial bones, bounds the cavities in which the eyes
are contained (orbits), and the nasal cavities. It consists of the
maxillary bones (Fig. 2, 12), the premaxillary bones (Fig. 3, 7,—in man
these 4 bones are fused together into one piece), the nasal bones, the
lachrymal bones, the ploughshare bone (vomer), the turbinated bones, the
cheek-bones (or malars, Fig. 2, 11), the palate-bones, and the lower jaw
(Fig. 2, 13). (The last originally consists of two symmetrical halves.)
The upper and lower limbs are built on the same type, and therefore
consist of corresponding parts (cp. Fig. 2). The more similar the
functions of the two pairs, the closer their resemblance. In the ox they
are much more alike than in man; in the bird, on the contrary, the
similarity is much less. A distinction can be drawn in both limbs
between the bony girdles (shoulder-girdle and hip-girdle), which serve
for union with the trunk-skeleton, and the different subdivisions of the
limbs themselves. I place side by side the parts of the arm and leg of
man.
ARM. │ LEG.
I. Shoulder-girdle, consisting │ I. Hip-girdle, consisting of:
of: │
Shoulder-blade (Scapula) (Fig.│ Hip-bone (Ilium) (24).
2, 17). │
Collar-bone (Clavicle). │ Pubis.
Coracoid process (of Scapula).│ Rump-bone (Ischium).
II. Upper arm: │ II. Thigh:
Upper arm-bone (Humerus) (18).│ Thigh-bone (Femur) (25).
III. Fore arm: │III. Leg:
Radius (19). │ Shin-bone (Tibia) (26).
Ulna (20). │ Clasp-bone (Fibula) (27).
IV. Hand: │ IV. Foot:
Two rows of wrist-bones │ Two rows of ankle-bones
(Carpal bones) (21). │ (Tarsal bones) (28).
Metacarpal bones (22). │ Metatarsal bones (29).
Finger-bones (Phalanges) (23).│ Toe-bones (Phalanges) (30).
The differences between arm and leg are explained by their different
uses. The bones of the leg, used to support the human body, are firmer
and thicker, but less movable than those of the arm, which is employed
in grasping. Consequently the union between the hip-girdle and the
trunk-skeleton is firmer than that of the shoulder-girdle. The radius
can rotate upon the ulna, so as to completely turn the hand over; a
similar twisting of the foot would not be of use, and cannot be
effected. The leg has a knee-pan (patella) (Fig. 31), with which there
is no bone in the arm to correspond. In the foot the toes are short, and
the remaining parts long; for instance, one of the tarsal bones, the
calcaneum (heel-bone), is strongly developed and projects behind (28*).
In the hand, the digits are relatively long, and since the tip of the
thumb can be made to touch the tips of all the fingers, are admirably
adapted for grasping.
[Illustration:
FIG. 2.—The Human Skeleton.
]
The number of fingers or toes is at most five, but may be less. The
horse has a single digit to each limb; the ox, two well developed and
two remaining as rudiments; the pig, two large and two small; while the
dog has four toes in the hind foot, five in the fore foot.
Man walks on the sole of the foot. Some other animals (dog, cat) on the
toes; others again (horse, ox, pig), on the tips of the toes. In the
last case there is not simply a horny structure (nail or claw) on the
upper side of the toe, but a hoof sheathing the whole of its tip. In
many animals the thigh and upper arm are drawn close up to the body, so
that the limbs appear quite different from those of man. (Compare Fig. 2
with Fig. 3.)
[Illustration:
FIG. 3.—Skeleton of an Ox. I. _Skull_: 1, Frontal bone, with horn
cores, _a_; 2, temporal bone; 3, malar or cheek-bone; 4, maxillary
bone; 5, lachrymal bone; 6, nasal bone; 7, premaxillary bone; 8,
lower jaw; 9, orbit; 10, occipital bone. II. _Neck and Trunk_: _H_,
7 cervical vertebræ; _R_, 13 thoracic vertebræ; _L_, 6 lumbar
vertebræ; _K_, sacrum; _Su_, caudal vertebræ; _C_, 13 pairs of ribs;
_D_, sternum. III. _Fore Limbs_: _Sc._, scapula; _A_, humerus; _S_,
radius; _E_, ulna; _U_, carpus; _M_, metacarpals; i., ii., iii.,
phalanges. IV. _Hind Limbs_: _B_, hip-girdle, _a_, ilium, _b_,
ischium; _F_, femur; _P_, patella; _T_, tibia; _Sp_, tarsus; _M_,
metatarsals; i., ii., iii., phalanges.
]
The bones are usually surrounded by flesh. This consists of a number of
different pieces united together by a delicate, elastic, fibrous mass
(connective tissue). The different pieces are termed _muscles_, each of
which is again made up of a large number of muscle-fibres, all taking a
longitudinal direction. Each fibre can contract, and a muscle becomes
shorter and thicker by simultaneous contraction of all its fibres. The
contraction and subsequent relaxation of muscles move other parts. There
are some muscles, the _hollow muscles_, which surround a cavity, and by
their contraction propel the liquid or solid substances found in their
cavity. The heart, for example, is a large muscle of this sort, serving
to propel the blood, while the hollow muscular coat of the gut moves on
the contained food. Other muscles are fixed by their ends to other parts
of the body, which they move by their contraction. We distinguish
between _dermal muscles_ and _skeletal muscles_, attached respectively
to the skin or by one end to an integumentary structure (hair, feather,
scale), and to parts of the skeleton. The animals which are devoid of
any internal skeleton, the _invertebrates_ (_i.e._ all animals except
vertebrates), naturally possess no skeletal muscles. Examples of _dermal
muscles_ are those by means of which a bird erects its feathers
(tail-coverts of peacock!), and those which enable a hedgehog to roll
itself into a ball and stick out its spines. Each end of a _skeletal
muscle_ is connected with a bone. If such a muscle contracts the more
easily movable bone is drawn towards the less easily movable one (Fig.
4). In order that the bones may be movable upon one another they are
united together by joints.
According as muscular movements are, or are not, under the influence of
the will, they are distinguished as _voluntary_ and _involuntary_. To
the latter kind belong the movement of the heart, and the movements of
the muscles in the wall of the gut by which the food is made to
progress.
[Illustration:
FIG. 4.—Bending of the Arm by Contraction of the Biceps Muscle. _a_,
humerus; _b_, ulna; _c_, elbow-joint; _d_, biceps muscle; _e_,
origin; _f_, insertion of the same. In the right-hand figure of the
muscle _d_ is contracted; in the left-hand figure it is slackened.
]
To destroy the contractile power of a muscle it is not necessary to
injure the muscle itself. Every muscle is related to a nerve, which
sends its fine branches to the fibres making up the muscle. If we cut
the nerve, the corresponding muscle loses its power of contraction. But
the nerve arises from the _central nervous system_, which in vertebrates
principally consists of the brain and spinal cord. The muscle will
therefore lose its contractile power if the connection with these
central parts is broken. The true cause of movement resides in these
parts. A sort of change, the essential nature of which is unknown to us,
takes place in them, and is propagated along the nerve to the muscle,
causing it to contract. The central nervous system is, therefore, the
origin, the centre from which the order to contract proceeds; hence its
name. The nerves which run from these central parts to the muscles are
known as the _nerves of movement_ (motor nerves).
[Illustration:
FIG. 5.—Diagram to explain the Action of the Motor and Sensory Nerves.
]
There is still, however, a second group of nerves, the _nerves of
sensation_ (sensory nerves), which arise in the sense-organs (skin,
mucous membrane of tongue, nose, ear, eye), and convey to the central
nervous system the impressions they receive from the outer world by the
aid of these sense-organs. In the appended diagram (Fig. 5), _C_
represents the central nervous system; _B.N._, a motor nerve, branching
in the muscle _M_; _G.N._, a sensory nerve, which runs from the
blood-bathed inner skin or dermis (_L.h._), underlying the outer skin or
epidermis (_O.h._), to the central system. (The arrows indicate the
direction in which impulses are conveyed along the corresponding nerve.)
Men or animals lose in weight if they take no food. The reason for this
is that certain substances leave the body either as gases (through the
lungs), or as liquids (by the kidneys and sweat-glands), without a
corresponding compensation. An animal or human being could not live
without taking in fresh substances, which, according as they are solid
or liquid, are known as food or drink. The different kinds of food and
drink, which, with few exceptions (salts, water), are taken from the
animal and plant kingdoms, cannot, however, _as such_, replace the
gradually diminishing body substance, for, to begin with, they contain
useless matters, which pass out of the body in the _fæces_ (dung). And
even the nutritious parts of the animal and vegetable substances taken
into the stomach, are not always in a form in which they can be used _at
once_. Digestion, which in all the higher animals takes place in a
_food-tube_ (gut), serves to reduce them to a suitable condition, at the
same time separating the useless matters. The action of several fluids
(saliva, gastric juice, bile, etc.) secreted by glands, extracts the
useful (nutritious) substances from the food and drink, converting them
also into a suitable form. The smaller the pieces into which the food is
separated, the better can this purpose be effected. In mammals the teeth
serve to break down the food; in birds and many Invertebrates the same
part is played by special secretions of the stomach or intestine
provided with hard ridges.
So long as the nutritious food-stuffs remain in the food-canal, even
though in a completely suitable form, they cannot nourish the body. And
since waste of the substance of the body everywhere takes place, it is
absolutely necessary that the food-stuffs should pass after digestion
into a system of organs going to all parts of the body. This system is
the _circulatory_, or _vascular system_. Food-stuffs enter it from the
gut directly or indirectly, reaching it in the latter case through the
_lymphatic_ (lacteal) system.
The _blood_ is the fluid into which the food-stuffs are taken up. It
consists of an almost colourless liquid, together with an innumerable
number of exceedingly minute blood-corpuscles.
The blood flows through the body in a system of tubes, or
_blood-vessels_, which branch repeatedly, and at last become merged in
the microscopic _capillary blood-vessels_. These capillaries are present
in nearly all parts of the body except the epidermis and epidermal
structures (hairs, feathers, scales, etc.). They have exceedingly thin
walls, which present no resistance to the passage of the nutritious
substances contained in the blood, so that these can be absorbed by
those parts of the body which lie between the individual capillary
vessels. The central organ of the circulation is the _heart_, an
enlarged part of the vascular system, possessing thick muscular walls.
By contraction of these, the blood is driven out of the heart (Fig. 6,
_H_); and its exit is possible on one side only (_a_), as at the other
side (_b_) there is a valve, which closes when the heart contracts. The
vessel into which the blood leaving the heart enters is termed an
_artery_ (_S.A._) It divides into several branches, also known as
arteries, and the smallest arteries pass into capillaries, which again
are connected with _veins_, which join larger and larger veins, until
finally one or a few open into the heart (_A_).
[Illustration:
FIG. 6.—Diagram of the Course of the Circulation.
]
Since the blood in the course of its circulation gives up some of its
nutriment to the various parts of the body, it would in the end become
useless for the purposes of nutrition if it did not receive a fresh
supply of food-stuffs from the gut, either directly or indirectly
(through the lacteal system). But apart from this, the blood would
ultimately become useless, and that very quickly, if it did not traverse
the lungs, kidneys, and sweat-glands. It is well known to every one that
a man or animal cannot live without air, or at any rate without a
certain gas, _oxygen_, that is contained in air. This oxygen must be
able to penetrate into the minutest particles of the body, and the
blood, in the corpuscles of which it is contained, carries it
everywhere. In the smallest particles (molecules) of the body an
oxidation (combustion) of body substance takes place, which not only
causes an evolution of heat, but also renders the body capable of doing
work. But if now the blood passes from the capillaries into the veins,
it contains too little oxygen. And besides, it has taken up from the
molecules of the body several substances, developed in those molecules,
which would be fatal to the animal if they were not removed from the
body. Now, when the blood streams through the lungs, it gets rid of the
poisonous gaseous matter, and when it traverses the kidneys and
sweat-glands it parts with the injurious liquid and solid substances.
But in the lungs the blood takes up at the same time fresh oxygen; and
since in this way the air in the lungs becomes poor in oxygen, the
_movements of breathing_ (respiration) provide for the passage of a
fresh supply of oxygen into the lungs. Only the higher Vertebrates
breathe by means of lungs; fishes and numerous aquatic Invertebrates
breathe by gills, and insects by air-tubes (tracheæ).
[Illustration:
FIG. 7.—The Small-winged Gall-fly, _d_ (_Andricus terminalis_), lays
its eggs separately in the rootlets of oak. Root-galls (_a_) result
from this, and inside of each of them a larva develops which, after
a metamorphosis, becomes a relatively large, wingless gall-fly (_c_)
known as _Biorhiza aptera_. This pierces the oak-buds in early
spring, and lays a large number of eggs in them; from part of the
bud is formed a large juicy gall (_b_), containing several larvæ,
from which the small-winged gall flies (_d_) develop. The species
here represented exist, therefore, in two forms, _e_ and _d_
(Heterogeny).
]
While _Nutrition_ is the life-process which shields the _individual_
from death, Reproduction serves to maintain the _species_. It is
familiarly known that the offspring generally resemble their parents.
But it is also a fact recognized by the stock-breeder, that a particular
animal will not only transmit several of its _own_ characteristics to
its offspring, but perhaps also various characteristics of the
grandparents or of animals belonging to still more remote generations,
although these characteristics are not visible in the animal which is
actually breeding (_Reversion_, _Atavism_). Among insects and the lower
animals there are species which, as adult animals, appear not in _one_
form, but two or several. In this case, as a regular thing, the
offspring does not resemble the parents, but the grandparents,
great-grandparents, or a still earlier generation. The older observers
have placed the offspring and the parents, and sometimes the
grandparents too, of the same animal species in different species, or
even genera or families, until newer researches on the reproduction and
development of these animals have proved them to belong to one and the
same species (see Fig. 7 and explanation). The method of reproduction by
which a species appears in two or several forms is distinguished as
_heterogeny_ and _metagenesis_, or _alternation of generations_. In the
first (Fig. 7) sexually reproducing animals alternate with other sexual
animals. It may be that these are of separate sexes, or else they may
possess both male and female organs (_hermaphrodite_). In metagenesis a
sexual generation regularly alternates with one or several generations
reproducing asexually.
The animal kingdom falls (cf. p. 2) into sub-kingdoms or main divisions.
Seven of these are commonly distinguished: I. Backboned animals; II.
Jointed-limbed animals; III. Worms; IV. Molluscs; V. Echinoderms; VI.
Cœlenterates; VII. Protozoa.
First Sub-Kingdom: VERTEBRATA (BACKBONED ANIMALS).
The Vertebrate body possesses a bilateral or twosided symmetry; _i.e._
it can be separated into two exactly corresponding halves, by a plane of
division. The bilateral symmetry is strictly carried out as regards the
external parts of the body, a single exception to this being flat-fish
(plaice, flounder, etc.); but, on the other hand, it is more or less
obliterated in the arrangement of the internal organs. In the Vertebrate
body we find, as an axis, a vertebral column (backbone) made up of
vertebræ, and traversed by the vertebral canal. As soon as this canal
widens out in the skull to the cranial cavity, the spinal cord, which it
contains, merges into the brain. In addition to the cavity containing
the central nervous system, and placed on the upper side (= dorsal side)
of the animal, a cavity, the _body-cavity_, is found in the under side
(= ventral side). It contains for the most part the organs of
respiration, circulation, digestion, and excretion (Fig. 1), and in
Mammals is divided by the diaphragm into _thoracic_ and _abdominal
cavities_. In all the other subdivisions of the animal kingdom the
central nervous system is situated in the same cavity as the
above-mentioned organs.
Various bones are connected with the vertebral column, and they serve
for the attachment of muscles. The bones collectively constitute the
skeleton, which is one of the most distinctive features of a Vertebrate.
The animals of this sub-kingdom never have more than four limbs, and
their blood is red, while that of most other animal groups is
colourless.
The structure of the heart in the various Vertebrates must also be
noticed. In no Vertebrate is this organ so simple in structure as in the
scheme given in Fig. 6; such an arrangement, moreover, would involve
great difficulties. One great difficulty would be that while the blood
was leaving the heart at _a_ (Fig. 6), no fresh blood could enter, so
that the blood in the veins would stand still. Even in the lowest
Vertebrates (the Fishes) this difficulty is obviated, for where the main
vein (or veins) opens into the heart an enlargement of this vein is
found, where the blood can collect as long as the heart continues to
contract. This expansion is also reckoned as part of the heart, and
named the _auricle_ (Fig. 8, _V.K._), while the heart proper is termed
the _ventricle_ (_K._). It is also easy to see that there must be a
tolerably wide opening between the two chambers, so that as soon as the
ventricle becomes flaccid the auricle can force blood into it. But there
being such a wide aperture between auricle and ventricle, one valve is
not enough to make it impossible for the blood to pass back into the
auricle during the contraction of the ventricular walls. There are two
or three valves there (Fig. 8, _Kl._) fixed by fibres to the wall of the
ventricle. In order that the blood which is forced into the artery
(_S.A._) may not pass into the ventricle during its relaxation, there is
another valve (not indicated in Fig. 8), at the base of the artery.
[Illustration:
FIG. 8.—Diagram of the Heart in a Fish.
]
An arrangement like that so far described is found in fishes. The heart
consists in them of an auricle, into which is returned the blood that
has traversed the body, and of a ventricle which moves it on again. But
the blood that has traversed the body is on that account poor in oxygen,
and consequently unfit to be circulated again when it is returned to the
heart. It is necessary for it to take up fresh oxygen before being
circulated again. In fishes this difficulty is met by the blood, poor in
oxygen, which flows out of the ventricle, first going to the _gills_ and
streaming through them. The gills consist of a very large number of
small, thin-walled outgrowths arranged in regular rows on the firm
gill-arches. The blood, poor in oxygen, passing out of the ventricle and
through various arterial branches to the gill-filaments, takes up fresh
oxygen as it streams through these from the oxygen dissolved in the
water which constantly surrounds them. For this purpose a stream of pure
water is regularly taken in by the mouth and expelled again, right and
left, through the gill-slits. The blood, having become rich in oxygen in
the gills, is now once more fit for circulation through the body, and
therefore flows out of the gill-capillaries into larger vessels, which
finally unite into a single large vessel that carries the purified blood
to the various parts of the body. In the arrangement of the heart here
described there is the disadvantageous condition that the blood is
obliged to traverse two sets of capillaries (gill and body capillaries).
This is not an easy matter, for there is a great deal of friction
between the blood and the walls of the capillaries, constituting a
hindrance to its progress. The circulation of the blood in fishes is
consequently very slow, and since the blood contains the oxygen which is
used by the various parts of the body, oxidation goes on slowly in the
body of a fish; hence the small amount of heat developed there. Since
fishes almost immediately give off to their surroundings the small
amount of heat which they develop, they have no constant body
temperature, varying in this respect with the temperature of the
surrounding water. Such animals are termed _cold-blooded_.
In all other Vertebrates a more rapid movement of the blood is rendered
possible by the insertion of a second heart, quite similar in every
respect to the other heart, in the course of the blood between the
respiratory organs and the body. The first heart drives the blood
through the lung capillaries, and therefore corresponds to the
fish-heart; from these capillaries the blood returns to the auricle of
the second heart, and from the ventricle of that heart travels to the
various parts of the body. When it has completed this course, it returns
to the auricle of the first heart. Although these two structures work
independently, they lie close together and make up a single organ. We do
not therefore speak of two individual hearts, but of one heart with two
halves. The first half, which receives the blood, poor in oxygen, that
is returned from the body, and sends it on to the lungs, lies on the
right, and is termed the _right_ half. The second half, which receives
the richly oxygenated blood from the lungs, and pumps it to the various
parts of the body, is termed the _left_ half (Fig. 9 and explanation).
In the arrangement just described, which is found in Mammals and Birds,
the blood returning from the lungs is propelled with new force through
the body, and therefore circulates very quickly, so that the various
parts receive a relatively large amount of oxygen in a short time. It is
therefore intelligible that Birds and Mammals develop more warmth than
Fish. They possess a special, constant body temperature, somewhat
different in different species, but usually lying between 98° and 104°
Fhr., and they are called _warm-blooded_ animals.
[Illustration:
FIG. 9.—Diagram of the Mammalian Heart. 1, right, 2, left ventricle;
3, right, 4, left auricle; 5, superior, 6, inferior vena cava; 7,
pulmonary artery forking into branches for right and left lungs; 8,
the four pulmonary veins; 9, the great body-artery (aorta); the
arrows indicate the direction of the blood-stream.
]
[Illustration:
FIG. 10.—Diagram of the Heart of a Reptile. Between the right (_r.K._)
and left (_l.K._) ventricles is a perforated partition. _r.V.K._,
right auricle; _l.V.K._, left auricle; _H.v._, vena cava, carrying
back the blood which has traversed the body into the right auricle;
_L.art._, pulmonary artery; _L.v._, pulmonary vein; _Ao._, aorta.
]
In Reptiles (snakes, lizards, etc.), the two halves of the heart are not
entirely distinct, since there is an opening in the partition-wall
between the two ventricles. As a consequence of this, the poorly
oxygenated blood of the right half of the heart mixes with the richly
oxygenated blood of the left half, the extent to which this mixing takes
place being proportional to the size of the aperture. In Reptiles,
therefore, the blood supplied to the lungs is not so poor in oxygen as
it might be, nor, on the other hand, is the blood supplied to the other
parts of the body completely oxygenated. As consequences of this: (1)
respiration is feebler, and (2) the development of heat less than in
Mammals and Birds (_i.e._ reptiles are cold-blooded), and (3) the
chemical changes taking place in the body (the metabolism) go on more
slowly than in warm-blooded animals, and we can understand why reptiles
execute fewer movements in a given space of time.
[Illustration:
FIG. 11.—Diagram of a Frog’s Heart. (The ventricle _K._ is quite
undivided: compare Figs. 9 and 10.) Other letters as in Fig. 10.
]
In Amphibians (_e.g._ frog) the two ventricles are similarly connected,
but the opening is still larger than in Reptiles, and the partition-wall
may even be altogether absent. It follows, therefore, that the mixing of
the two kinds of blood is still more complete, and that Amphibians, too,
are cold-blooded.
The vertebrate sub-kingdom embraces the classes of I. Mammals; II.
Birds; III. Reptiles; IV. Amphibians; V. Fishes.
CLASS I.: =MAMMALIA= (SUCKLERS).
Warm-blooded Vertebrates (p. 16), usually covered with hair, and
bringing forth living young, that suck for some time after birth. The
female is provided with milk-glands on the thorax or abdomen, or both
those regions.
Speaking quite broadly, the skeleton is like that of man, described on
pp. 4–8. There are, however, great differences in detail. The cranium is
relatively much smaller, and the bones of the face (especially of the
jaws) are usually much larger than in the human skull. The number of the
cervical vertebræ is seven in all Mammals, as in man; but the other
kinds of vertebræ vary in number in the different species. The number of
caudal vertebræ, for example, is very variable. As most Mammals go on
all fours, their fore and hind limbs are much more similar than is the
case in man. In many the thigh and upper-arm bones are drawn closely up
to the body (horse, ox, pig). Mammals never have more than five fingers
or toes, but may have fewer. The thumb or great toe is the first to
disappear (hind foot of dog, fore and hind foot of pig). There may be
only three (rhinoceros), two (ox, sheep), or one (horse) digit
developed. In addition to fully developed digits, there are in many
Mammals very small stunted ones (“dew-claws” of the stag).
[Illustration:
FIG. 12.—Vertical Section of a Human Grinding Tooth.
]
[Illustration:
FIG. 13.—Crown of a Grinder of the Ox. _a_, cement; _b_, enamel; _c_,
dentine; _d_, enamel; _e_, cement.
]
There are also great differences in the way of resting the feet on the
ground. Man and bear tread on the soles of the feet (plantigrade); dog
and cat walk on the under side of the toes (digitigrade), not on the
other parts of the feet. Ox, pig, horse, etc., rest while walking only
on the tips of the toes, which are sheathed in hoofs (unguligrade).
The teeth of mammals are wedged into special sockets in the jaw-bones.
The structure of a mammalian tooth is made clear by Fig. 12. We first
distinguish a pulp-cavity (_p_), which in the living animal is filled
with a substance supplied by a bloodvessel and nerve. This cavity is
surrounded by the dentine (_d_), a hard substance which makes up the
greater part of the tooth. Hard enamel (_s_) covers the whole of the
crown in man and many animals, while in certain other forms it is found
only on part of the crown. The root of the tooth is covered with cement
(_z_), a bone-like substance.
All teeth in which the entire surface of the crown is covered by enamel
only are known as _simple teeth_, while those into which the enamel only
penetrates in more or less deep folds, leaving the rest of the crown
uncovered, are known as _compound teeth_ (Fig. 13). The structure of the
teeth is related to the nature of the food. We distinguish three kinds
of teeth in the same animal, which, however, are not all present in
every species; these are the _incisors_, _canines_, and _grinders_. The
first two kinds are changed; but only the anterior grinders, known as
the _premolars_, are changed, while the hinder ones, the _true molars_,
do not first appear as “milk” teeth, but rather later on with the other
“permanent” teeth.
The following orders of Mammals are distinguished: I. Bimana (Man), II.
Quadrumana (Apes), III. Carnivora (Beasts of prey), IV. Insectivora
(Insect-eaters), V. Cheiroptera (Bats), VI. Rodentia (Gnawers), VII.
Ruminantia, VIII. Solidungula, IX. Pachydermata, X. Cetacea, XI.
Edentata, XII. Marsupialia (Pouched animals), XIII. Monotremata.
I shall deal here only with those orders which are of agricultural
importance.
ORDER: =Carnivora= (BEASTS OF PREY).
In each jaw there are six relatively small incisor teeth; and, on each
side of these, a large projecting canine, by which the flesh is torn
from the body of the prey (Fig. 14). The premolars and the first of the
true molars (the carnassials[2]) are strongly compressed, and have a
cutting crown; their outer surface is completely covered with hard
enamel. As the lower jaw is smaller than the upper jaw, and is only able
to move up and down, not from side to side, the sharp crowns of the
premolars, and especially those of the large carnassials, cut along one
another, and divide anything coming between them as if with shears. The
small molars which are usually found behind the carnassials have broad
tuberculated crowns. The temporal (_i.e._ chewing) muscles are strongly
developed, the general result of which is that the head is broad. The
claws are very sharp in some of the families. The Carnivora are powerful
animals, move very quickly, and are endowed with keen smell and sight.
Footnote 2:
The upper carnassials = last premolars.
The lower „ = first molars.—TR.
The wild Carnivora living in Britain belong to the families of cats,
dogs, and weasels.
Family: =Felidæ= (_Cat Family_).
Typical Carnivora with very large canines and carnassials, two premolars
in each half of each jaw, one of the upper molars, but none of the lower
ones, small and tuberculated. Tongue rough. Fore and hind feet
five-toed. When not in use, the claws are drawn back (retracted). The
Felidæ are digitigrade. Backbone very flexible, and with free power of
movement. The Felidæ are bloodthirsty, nocturnal animals, many of which
climb well, and spring upon their prey.
The group is specially exemplified by the =Domestic Cat=, the parent
stock of which is the Nubian cat (_Felis maniculata_), a native of Nubia
and the Soudan. The =Wild Cat= (_Felis catus_) is larger than the common
kind, and has a thicker tail. Formerly it was tolerably common in
Britain, but now only occurs in a few thinly populated districts.
[Illustration:
FIG. 14.—Skull of Domestic Cat.
]
The =Lynx= (_Felis Lynx_), found at one time in Germany, still lives
in the Carpathians, and in Switzerland, but occurs more commonly in
Scandinavia, Denmark, and Russia.
Family: =Canidæ= (_Dog Family_).
Head longer than in cats; canines and carnassials relatively less
developed. Two tuberculated molars on each side of each jaw. Claws not
so sharp as those of cats, and cannot be drawn back (_i.e._ are
nonretractile). Fore-foot five, hind-foot four toes. Tongue smooth.
The various races of the =Domestic Dog= belong here.
The wolf (_Canis lupus_) is no longer an inhabitant of Britain or
Germany, but sometimes crosses the German frontier from Russia,
Galicia, Hungary, the Alps, and the Ardennes, especially in winter,
and preys upon the larger domestic animals.
The remaining example is—
=The Fox= (_Canis vulpes_).
This animal lives in an underground dwelling, which is either dug out by
itself or else is a deserted badger-burrow. It kills roes, fawns, hares,
and game-birds; in farms it preys on poultry and eggs. It never commits
depredations in the neighbourhood of its burrow, for fear of betraying
its hiding-place. Valuable services, however, must be balanced against
the damage mentioned above, for it catches many rabbits, and also an
enormous number of field-voles in the years when these become a pest. It
also often eats insects (_e.g._ cockchafers), worms, and snails. In
fact, the fox is perhaps generally of more use than otherwise to the
farmer and forester.
Family: =Mustelidæ= (_Weasel Family_).
Elongated, slender; legs short; head small and flat; cranium elongated;
tongue smooth. Five toes on each foot, with small, sharp claws. A
tuberculated molar on each side in the upper and lower jaws. The weasels
give out an offensive odour from stink-glands situated near the anus.
There belong to this family—
1. The =Pine Marten= (_Mustela martes_). Body up to twenty inches, tail
up to ten inches long; fur brown, with yellowish wool-hairs; a yellow
patch on the throat. Is found in thick woods, where it destroys small
birds and squirrels; it also kills much poultry and game.
2. The =Beech=, or =Stone Marten= (_Mustela foina_). About as large as
the preceding species; greyish-brown fur, with whitish wool-hairs; a
white patch in the throat; chiefly occurs in the immediate neighbourhood
of human dwellings, in barns, wood-stacks, etc.; kills a great deal of
poultry, sometimes also wild birds, mice, and game.
3. The =Polecat= (_Putorius fœtidus_). Shining brownish black, with
yellow wool-hairs; somewhat smaller than the stone marten; in
particular, the tail is shorter and its hair is not so long as in the
two preceding species. In the summer it lives in the open country, in
hollow trees, or in the burrows of foxes and rabbits; in winter it
settles down near human dwellings, where it lives in wood and under
heaps of brushwood, haylofts, etc. In summer it may do more good by
destroying numerous field-voles, water-rats, etc., than harm by
devouring those singing birds which are favourable to agriculture; but
in winter its undesirable visits to the fowl-house and dove-cot effect
much injury. It kills the birds and devours the eggs, sucking without
smashing them. In winter, too, it is very harmful to beehives, being
fond of honey.
[Illustration:
FIG. 15.—The Pine Marten (_Mustela martes_).
]
The =Ferret= (_Putorius furo_) is undoubtedly a short-legged variety of
the common polecat, usually white in colour, and, when that is the case,
red-eyed.
4. The =Stoat=, or =Ermine= (_Putorius erminea_). Body twelve inches,
tail about three and a half inches long; slender; the body is scarcely
broader than the head; tail longer than in the next species; summer fur,
cinnamon brown above, white below; tail, cinnamon brown with black tip;
winter fur quite white, but the end of the tail remains black. Mostly in
fields, in the neighbourhood of plantations or woods; always abundant
among sandhills, owing to the rabbits living there. The stoat usually
follows its prey at night, stealing upon mice, rats, rabbits, hares, and
song-birds; it is also sometimes very destructive in dove-cots and
hen-houses. It must, however, be stated that the stoat is on the whole
more useful than harmful.
5. The =Weasel= (_Putorius vulgaris_). Smaller than the stoat; head
larger and thicker than the extremely slender, almost snake-like, trunk;
legs short. The weasel is a very sharp little animal, and can easily
pass along mouse-holes. Summer and winter coats alike—back brown, belly
white. Its food chiefly consists of field-voles, also of rats and
water-rats, young hares and rabbits, birds building near the ground, and
also their eggs, which the weasel, by holding under its chin, manages to
carry to its home; occasionally also lizards, blindworms, snakes, and
frogs. The weasel does some damage in fowl-houses and dove-cots, and is
also destructive to game. This, however, does not outweigh its very
great use, since it is above all an untiring vole-catcher. When in any
region the field-voles have multiplied excessively, an immigration of
weasels takes place from surrounding parts. In years when there is a
plague of voles the usual breeding time in spring is followed by another
later on. A very large number of weasels may be found in a vole-infected
district, and they thin out the mischievous rodents in a surprising
manner. Nor are the weasels less useful in summer than in winter. They
even follow under the snow the voles which winter in the country, and
the slaughter effected at this period must exert a great influence on
the following season, when these animals recommence their injurious
work, and a pair of them that have survived the winter may perhaps
produce two hundred others before the end of the summer.
6. The =Mink= (_Putorius lutreola_) is as large as a polecat, and may
be regarded as a sort of link between it and the others. Leg and ears
short; skin smooth-haired, brown both on the back and the belly; chin,
lips, and a small patch on the neck, white; tail about one-third the
length of the body. In well-watered regions on the banks of rivers,
lakes, and ponds. Eats water-rats, water-birds, frogs, salamanders,
fish, crayfish, water-insects, water-snails, and aquatic bivalves.
Holstein, Mecklenburg, Pomerania, Brandenburg, Silesia.
7. The =Otter= (_Lutra vulgaris_). Body flattened; legs short, with
webbed toes; snout rounded; ears short, and can be closed by a fold of
skin; tail flat, and pointed at its tip. Length of the body,
twenty-eight to thirty-two inches; of the tail, fourteen to sixteen
inches. Skin smooth-haired, shining dark brown above and below. Found on
the banks of lakes, pools, ponds, rivers, brooks, etc., where fish is
plentiful. It catches water-rats, ducks and geese, as well as their
young, wild water-birds, frogs, fish, crayfish, water-insects.
Especially destructive to fish.
8. The =Badger= (_Meles taxus_). Body heavy; legs short, plantigrade;
toes with strong digging claws; snout pointed; canines not very large;
both they and the carnassials much worn in old animals. Tuberculated
molars well developed. The dentition and whole structure of the body
show that the badger is not exclusively a flesh-eater. Length of body,
three feet; weight, 22 to 33 lbs. Fur tolerably long-haired, yellowish
whitey grey, mixed with black. Head with longitudinal stripes of black
and white; tail short, yellowish grey.
The burrow is very large; several passages, the openings of which may be
ninety-seven feet apart, lead to the exterior. The badger only leaves
its dwelling in the evening. It eats mice, birds which nest on the
ground, especially their eggs and young, snakes, frogs, cockchafer
grubs, earthworms, insects; also turnips, carrots, acorns, and sweet
fruits. Although it is both harmful and useful, the latter is more
generally the case. Its digging habits, however, are sometimes
destructive, since it throws up young trees and other plants by the
roots. The badger often sleeps several days in succession during the
winter, although it does not hibernate. Its fat is used up during the
winter.
ORDER: =Insectivora= (INSECT-EATING MAMMALS).
Since the Insectivora feed upon very small animals (insects, worms,
snails), they cannot themselves be large. Only those species (hedgehog)
which feed on small mammals and birds or upon vegetable matter, in
addition to insects, are of medium size. The native species all live on
or in the ground. The snout is extremely slender, and does duty as an
organ of touch. The eyes are usually very badly developed. Incisors
sharp; and the back teeth, which are completely coated with enamel, are
remarkable for their pointed crowns. When the mouth is closed the upper
teeth fit into the spaces between the lower teeth, and _vice versâ_.
Consequently the shutting of the mouth forces the points of all the back
teeth into any insect which happens to be between the jaws. The
Insectivora are plantigrade (p. 22). Here belong the following forms:
the Shrews (_Sorex_), the Mole (_Talpa europæa_) and the Hedgehog
(_Erinaceus europæus_).
[Illustration:
FIG. 16.—Skull of the Mole.
]
The =Shrews= (_Sorex_) are small animals with a superficial resemblance
to mice, with slender soft-haired bodies, small eyes, and tolerably
long, thickly haired tails. Shrews are extremely voracious, eating daily
more than their own weight of food, and destroying an enormous quantity
of subterranean vermin. They live in underground passages, not usually
made by themselves, but dug out by field-voles. They smell strongly of
musk, secreted by two glands in the hinder part of the body.
The blackish brown Shrew-mouse, or =Common Shrew= (_Sorex vulgaris_),
and the =Lesser Shrew= (_Sorex pygmœus_), only about two inches long,
kill, in the cornfields, gardens, or woodland, an enormous quantity of
noxious insects found in the earth, together with their larvæ; also
snails and worms, and sometimes field-voles, and are in the highest
degree serviceable. But the larger (up to 3½ inches long), black =Water
Shrew= (_Sorex fodiens_), although serviceable on land in the same way
as the other kinds, is very injurious to fishing and fish-breeding,
since it devours the small fish and kills the larger ones, eating out
their eyes and brains.
[Illustration:
FIG. 17.—The Common Shrew (_Sorex vulgaris_).
]
The =Mole= (_Talpa europœa_). Body thick, cylindrical. Legs short, fore
legs broad and spade-like, with broad digging claws. Eyes small,
scarcely visible among the fur. No external ears; the auditory opening
can be completely closed by a fold of skin. Shining black fur. The mole
is found in every soil inhabited by insects and earthworms, provided it
is not too stiff, but yet sufficiently coherent to dig passages in,
which will not at once collapse. Its presence is known by the heaps
which it throws up. The nest, however, is always found under a larger
heap, frequently hidden under tree roots, walls, etc., though sometimes
in the open field. It consists in the first place of a nearly round
dwelling-chamber, softly upholstered with vegetable substances; this is
surrounded by a labyrinth of passages. From the nest a passage runs to
the mole’s hunting-ground. The walls of this passage of the labyrinth,
and of the nest, are hard. The wider and subterranean channels, which
the mole digs out when it is simply catching insects in the soil, easily
fall in again, and the animal takes no pains to compact their walls. The
highway to the hunting-ground, in which the animal can progress very
rapidly, can be at once detected, not like the ordinary passages by a
small chain of mole-hills composed of the thrown-up earth, but by a
depression, since in its preparation the earth is laterally compressed
and not thrown out. This tube is shorter or longer according as the
hunting-ground is in the immediate neighbourhood or further off; it may
be 100 or 160 feet long. The mole sleeps in the nest during the time not
employed in seeking for food, and goes three times a day on the hunt for
insects (early morning, midday, and before sunset in the evening).
Having reached the subterranean hunting-ground, it tracks to some
distance the insect larvæ, and worms found in the soil, being aided in
this by its long snout. It daily devours more than its own weight.
During summer the mole digs its passages near the surface, since larvæ
and worms are then found in the uppermost layer of earth. In winter,
when these withdraw into the depths of the soil, it digs much deeper
channels. It does not fall into a winter-sleep. The young (three to
seven) are born in May, June, or July. The mole never gnaws plants. It
does service, sometimes very great, by eating many wireworms, grubs,
snail embryos, earth caterpillars, mole-crickets, and other
earth-inhabiting insects, as well as their larvæ. It also willingly eats
earthworms, but whether this does good is not definitely known. But
under certain conditions it may also do harm, rooting up plants as it
makes its heaps. Grass and grain suffer little, if at all, by this;
other plants more; while young flax-plants perish if their roots are
loosened. Mole-hills in hayfields and cornfields are a nuisance at
harvest time. Moles are not to be endured in the neighbourhood of dams,
since their borings may become the immediate cause of flooding. Trapping
may usefully be resorted to in cases where moles are harmful.
The =Hedgehog=, or =Hedgepig= (_Erinaceus europæus_). When danger
threatens it rolls itself into a ball covered all over with prickles,
and is in this way secured from the attacks of most enemies. The
hedgehog goes on the hunt in the evening; while during the day it sleeps
in its hiding-place, situated in such places as the side of a ditch,
hedges, or under heaps of brushwood. It preys more particularly on
field-voles, sometimes also on eggs and small birds (chickens
occasionally), lizards, grass-snakes, adders (by the bites of which it
is unaffected), frogs, cockchafers and their larvæ, field snails,
earthworms, and similar small deer; now and then on fallen fruit and
juicy plant roots.
ORDER: =Cheiroptera= (BATS).
[Illustration:
FIG. 18.—Skeleton of a Bat.
]
All Bats, except a few tropical genera, feed on insects, and possess
teeth like those of the preceding order of Mammals (p. 30). The leading
feature is the characteristic modification of the fore limbs into a
flying apparatus. The bones of the fore arm (Fig. 18, _u, r_), the
metacarpels (_mc_), and the phalanges (except in the case of the thumb,
which possesses a sharp claw (_p_)) are of great length; and between the
long fingers, between the fore and hind limbs, and, last of all, between
the two hind limbs there is an elastic membrane, serving both for flight
and touch. Sight ill developed, since the bat is a nocturnal animal; a
delicate sense of touch has its seat not only in the flying-membrane,
but also in the skin of the ears, which are often very large, and in the
membranous flaps which, in a few genera (the “leaf-nosed” bats), occur
on the nose and lips. As is well known, bats sleep in the day; and they
also hibernate in chimneys, hollow trees, ruins, and other similar
places of concealment.
They principally devour night-flying moths, and spiders; and, since they
use a great quantity of nourishment, are of great service, since the
caterpillars of many of the species they destroy are very injurious to
agriculture or forestry. About nine species live in Britain, but there
is no use in enumerating them here.
ORDER: =Rodentia= (GNAWING MAMMALS).
[Illustration:
FIG. 19.—Skull of Squirrel.
]
Two long incisors (Fig. 19), the crowns of which are continually being
worn down, while a corresponding growth takes place at the root-end.
These incisors are used for gnawing, in which process the lower jaw is
rapidly moved backwards and forwards. Gnawing wears down these teeth
less in front than behind, owing to the presence of a thick layer of
enamel in the former position. Their crowns, therefore, maintain a
chisel-edge. That the incisors never stop growing is clearly seen when
the usual wearing down does not take place, as, _e.g._, when the lower
jaw is placed obliquely under the upper jaw, or when a tooth is absent
in one jaw, under which circumstances the corresponding incisor in the
other jaw is not worn down. In such a case the incisors continue to
grow, ultimately curving upwards or downwards, and becoming tusk-like
structures (Fig. 20). The Rodents have no canines. In those Rodents
which feed both on animal and vegetable food (the “Omnivora,” _e.g._
squirrel, common mouse, brown rat, etc.), the crowns of the back teeth
are completely covered with enamel; in the purely vegetable feeders
(“Herbivora,” _e.g._ hare, rabbit), they are compound teeth (p. 22). In
most Rodents the hind feet are longer than the fore, giving a springing
gait. Eyes large. Many forms have “cheek-pouches,” in which the food
they obtain can be stored up for some time. When the pouches are full, a
muscle contracts by which their ends are drawn backwards; they are
emptied by the animal pressing them with its fore feet. The majority of
Rodents are small, they are at most of medium size (hare). The majority
of the species have great powers of reproduction, by which the injurious
kinds are sometimes rendered a very great pest. The British forms
injurious to agriculture principally belong to the families of hares,
mice, and voles. The squirrel (_Sciurus vulgaris_), and the dormice
(especially _Myoxus avellanarius_) are solely of importance in forestry.
Family: =Leporidæ= (_Hares and Rabbits_).
Skull somewhat long. Two small incisors behind the two large upper ones.
Ears long and spoon-shaped. Upper lip cleft. Back teeth with enamel
folds. Here belong the hare (_Lepus timidus_) and rabbit (_Lepus
cuniculus_).
=Hare= (_Lepus timidus_). Ears longer than the head. Eyes yellowish
brown. Fur rusty yellow to grey on the upper side, white on the under
side. The doe litters in an open “form;” the young are born covered with
hair and with open eyes. Mature animals breed four or even five times a
year, producing two to four leverets each time. The hare is injurious to
agriculture, eating cabbages, rape, turnips, clover, vetches, young corn
plants, carrots, and grass. It also eats many weeds. It is, however,
less injurious than the rabbit, for it does not burrow. The damage done
by the hare is also less evident, since this restless, fastidious animal
seldom feeds continuously in the same spot.
[Illustration:
FIG. 20.—Abnormal Tooth in Hare.
]
=Rabbit= (_Lepus cuniculus_). Ears shorter than the head. Eyes dark
brown. Fur yellowish brown to greyish yellow on the upper side, redder
in front. Under fur bluish grey. Shape more compressed. The rabbit
breeds more rapidly than the hare. Five to six times yearly the doe
brings forth four to eight young, which, after six months, can again
reproduce. Dwelling subterranean. Young, blind and hairless at birth. As
the rabbit burrows, it is limited to certain districts, for the soil
must not be too stiff and firm, nor, on the other hand, too light and
incoherent. The rabbit is injurious in the same way as the hare, but the
damage is more obvious (see above); and as a result of its burrowing
habits it does infinitely more damage. Both in sandhills and in alluvial
sandy soil rabbit burrows lead to the blowing away of material only held
together by sand-plants. Kept down by shooting, netting, and ferreting
(p. 27).
Family: =Muridæ= (_Mouse Family_).
The mouse-like animals (the larger species of the family are called
“rats”) closely resemble the representatives of the following family,
but are distinguished from these (the “voles”) by their slender body,
longer legs, a more pointed head with longer always clearly visible
ears, and usually, with the exception of the hamster, by a tail equal in
length to the body. The hind legs are longer than the fore legs, hence
the hopping mode of progression. Three back teeth on each side of each
jaw, possessing a tuberculated crown completely covered with enamel.
[Illustration:
FIG. 21.—The Hamster (_Cricetus frumentarius_).
]
The =Hamster= (_Cricetus frumentarius_).—The Hamster has
cheek-pouches, and a very short, thick, but short-haired tail. It
attains the size of the brown rat. Bright yellowish brown; belly and
legs black. The hamster is found almost exclusively on fertile soil
devoted to cultivation. It appears locally, and then for several years
in great abundance, so that it is often caught in tens or even
hundreds of thousands. Favourite food: wheat, field beans, and peas,
then rye and similar grain; and, last, roots, turnips, young corn
plants. Sometimes, too, the hamster eats animal food—worms, insects,
lizards, small birds, eggs, and mice. As a winter store it usually
only accumulates grain, beans, and peas in its hiding-place, often to
the amount of more than five gallons. A little heap of thrown-out soil
marks on the surface the position of its nest. The entry to this runs
vertically down into the soil. Six to twelve young, twice a year. The
dwellings of the hamster, which are situated in stubble-fields, can
easily be found; and by digging them up, particularly in spring and
late summer, when there are young ones, the number of these
destructive Rodents can be greatly reduced. May be caught in traps.
=Genus Mus= (Mice and Rats) includes Rodents without cheek-pouches, and
with long, scaly, ringed tails. Two large species (“rats”) belong here,
namely—
The common =Black Rat= (_M. rattus_), indigenous to Europe since
pre-historic times, and the stronger, somewhat larger—
=Brown Rat= (_M. decumanus_), with greyish white belly (while the
first-named species is black on the upper and only slightly brighter on
the under side). The brown rat migrated during the first half of the
eighteenth century from Asia into Russia, and about the same time from
Further India to England by means of ships. Since then it has spread all
over Europe and other parts of the world, and in many regions has quite
driven out the black rat. Both kinds of rat eat almost everything, and
are a pest in housekeeping, as well as in agriculture. They feed on
insects, mice, eggs, and chickens, will even bite pieces from the living
bodies of grown poultry and fattening swine, and also devour young geese
and ducks. They eat grain, peas, beans, potatoes, carrots, turnips;
bread, cheese, and similar provisions. Multiply very rapidly. Can be
driven away by clacking-mills, and to a great extent by noise. Caught in
traps.
Besides these, four mice belong here:—
The =Common Mouse= (_Mus musculus_). Back yellowish grey-black,
gradually shading into a somewhat lighter tint on the under side.
[Illustration:
FIG. 22.—The Long-tailed Field Mouse (_Mus sylvaticus_).
]
The =Wood Mouse=, or =Long-tailed Field Mouse= (_M. sylvaticus_). Back a
brown shade of yellowish grey; belly white, sharply marked off;
relatively very long hind legs, hence a hopping gait. The long-tailed
field mouse penetrates tolerably far into woods, but is also found in
plantations and gardens, sometimes also in quite treeless regions. On
arable land it may adopt the habits of the field vole (p. 42), but as it
does not multiply so rapidly is not nearly so injurious. It may also
live either for a short time or permanently in houses, adopting the same
habits as the common mouse.
The =Harvest Mouse= (_M. minutus_). Small, pretty; back yellowish brown
red, belly of a sharply marked-off white. Lives in cornfields during the
summer; in harvest time by the field-paths; during winter in barns and
haystacks, but also in outdoor nests in the fields. Climbs among the
grass and corn-haulms, and the small stems and branches of other plants,
including shrubs, holding fast, not only by the feet, but also by the
tail. Builds a beautiful spherical nest with a side entrance out of the
haulms and leaves of grass and corn, or out of other leaves. Devours
seeds, especially grain, oats being the favourite.
The =Corn Mouse= (_M. agrarius_). Back brownish red with longitudinal
black stripes. In plains east of the Rhine. Usually local, but then very
abundant. Chiefly in cornfields and fruitfields; digs holes in the soil.
In autumn it often occurs in the field in large colonies. Food: grain,
beans, peas, potatoes, turnips, carrots. In winter in the barns and
dwelling-houses of farmers.
[Illustration:
FIG. 23.—Upper Back Teeth of Brown Rat, seen from grinding surface.
]
[Illustration:
FIG. 24.—Upper Back Teeth of Water Vole, seen from grinding surface.
]
Regarding the means of destroying those mice which are sometimes
damaging to agriculture (_M. sylvaticus_ and _M. minutus_), see methods
mentioned under “Field-vole” (p. 43).
Family: =Arvicolidæ= (_Vole Family_).
The large voles are also popularly called “rats,” the smaller ones
“mice.” They closely resemble the true mice and rats (p. 38), but are
distinguished from them by their plumper, more compressed body; a
thicker head with blunt snout, and ears quite hidden in the fur; and a
short, tolerably hairy tail, on which no rings of scales can be
distinguished. There are on each side of each jaw three back teeth, of
which each appears to consist of two rows of three-sided prisms, fused
together along the middle line (cp. Figs. 24 and 23). The native species
all belong to the genus _Arvicola_; the Bank Vole (_Arvicola
glareolus_), the Water Rat, or Water Vole (_A. amphibius_), and the
Short-tailed Field Mouse, or Field Vole (_A. agrestis_).
The brownish-red =Bank Vole= (_A. glareolus_) occurs in forests.
The =Water Rat=, or =Water Vole= (_A. amphibius_). Body six inches long,
tail half the length of the body. Fur of one colour, brighter on the
under side, varying from brownish grey to brownish black on the back,
and from whitish to greyish black on the belly. On the banks of rivers,
brooks, ditches, canals, etc.; also on damp low-lying meadows and
fields. Digs much-branched passages in the soil; this often takes place
in embankments to such an extent that it finally leads to their complete
destruction. The vole also does damage in grass-fields and cornfields in
the same way as the mole (p. 33). In its case, however, there is no
compensating service. It certainly eats insects and worms, but its chief
food is of vegetable nature; grain, potatoes, turnips, and carrots are
devoured by it in large quantity, and in particular stored up in its
hiding-place. It also destroys the roots of grass and corn, and eagerly
devours chickens and the eggs of ducks and geese. A variety (_A.
amphibius_, var. _terrestris_) occurs in dry soils, and is distinguished
by its smaller size, lighter colour, and shorter tail. Its habits are
the same as those of the ordinary form, but it is more given to
attacking trees.
Traps, shooting, poisoning with celery stumps hollowed out and filled
with phosphorus, or else with phosphorus paste.
The =Field Vole=, or =Short-tailed Field Mouse= (_A. agrestis_). A small
animal, with dark brownish grey back and greyish white belly. [Lives in
pastures, especially those which are low-lying and damp. Large numbers
are found together, and they make deep burrows in the soil, each pair
having a special nest to themselves. Three, four, or even more litters
per year; four to ten young in each litter. Its favourite food consists
of roots, young shoots of grass, etc., and the tender bark of shrubs,
but nothing of vegetable nature comes amiss. Specially destructive in
permanent pasture.]
REMEDIES. (_a_) _Preventive measures_. Protection of its natural enemies
(weasel, stoat, polecat, fox, hedgehog, owls, buzzards, kestrels, the
smaller seagulls). Catching in traps, etc., in the spring, when the
voles are only present in small numbers.
(_b_) _Destructive measures_, which should be as generally used as
possible in infested districts. If a field has been completely
devastated, or the crop is over: (1) Working the soil with a spiked
roller; (2) Partial inundation of the lower-lying fields. If it is
desired to kill the voles and spare the crop as well, the following
means may be recommended: (1) The digging of cylindrical holes six
inches across and two feet deep, especially at the margins of the fields
and in the furrows, as well as—at harvest time—on any footpaths that may
be found. The voles fall into these holes, cannot get out again, and are
starved. (2) The employment of poisons. (Care must be taken that no
children or domestic animals are poisoned.) Phosphorus paste is best.
[Illustration:
FIG. 25.—The Southern Field Vole (_Arvicola arvalis_).
]
The =Southern Field Vole= (_A. arvalis_) plays the same destructive
part on the Continent that the preceding form does here (Fig. 25).
_Remedies_—see above.
ORDER: =Ruminantia= (CUD-CHEWING MAMMALS).
The feet end in two hoof-covered toes, besides which two “after toes”
are present. The upper incisors are absent, with few exceptions, but
many deer have canines in the upper jaw. The back teeth of Ruminants are
compound teeth. The lower jaw is smaller than the upper, and during
chewing undergoes lateral movements, so that the plants taken in as food
are ground up, as it were, into small pieces, between the projecting
enamel ridges of the upper and lower back teeth. The stomach consists of
four subdivisions; these are (1) the rumen, or paunch, where the greater
part of the food and water taken collects; (2) the reticulum, or
honey-comb stomach; (3) the psalterium, or manyplies; (4) the abomasum,
reed, or rennet stomach. The last is the second largest part, and in it
the same chemical changes take place as in the simple stomach of a
non-ruminant. After the food has remained for some time in the paunch it
passes up again through the gullet, and [as the “cud”] undergoes a
second chewing. The soft mass resulting is once more swallowed, and
passes into the psalterium and abomasum.
[Illustration:
FIG. 26.—Skull of a Sheep.
]
Not only the families of _Tylopoda_ (Camels, Llamas), and
_Camelopardalidæ_ (Giraffes), but also the large family of _Cavicornia_,
to which, amongst others, the ox, sheep, and goat belong, will be passed
over in this book. I need only mention the—
Family: =Cervidæ= (_Deer Family_).
Deer have branched horns, known as antlers. With the solitary exception
of the reindeer, they are only found in the males. They are bony
structures borne upon projecting knobs (horn cores) of the frontal
lines. After each rutting-season the antlers are cast, new ones, clothed
at first with a soft skin [the “velvet”], are developed. Before the next
rutting-season the dermal part of the skin unites firmly with the
underlying antler, and becomes itself ossified, while the epidermis
shrivels up, partly peels off in bits, and is partly rubbed off by the
animal against tree trunks. If the conditions of life (food, weather)
are favourable, the animal acquires a new side branch to each antler
every year, at any rate, so long as he continues to get bigger and
stronger. The one-year-old male (“brocket”) has therefore a simple
unbranched antler, the two-year-old (“spayad”) one side branch as well,
the three-year-old (“sorel”) three points in all; the four-year-old
(“staggard”) has four points; the five-year-old (“stag”) five, and so
on.
[Illustration:
FIG. 27.—Development of Roebuck Antlers.
]
In Britain two indigenous deer are found—the Red Deer (_Cervus elaphus_)
and the Roebuck (_C. capreolus_); a third species, the Fallow Deer (_C.
dama_), lives in South Europe and Asia Minor [and the exact date of its
introduction into Britain is not known].
The =Red Deer= (_Cervus elaphus_). Six to seven feet long, and four feet
high. Antlers rough and cylindrical for their entire length; each in its
normal condition has two front branches [“brow” and “bez-tyne”], a
middle branch [“tres”], and a “crown.” Tail small. Body of a brownish
colour, becoming red in summer. A light yellowish brown spot on the
tail. Male larger than the female, with long dark hairs on the neck
during the breeding season (autumn). The young (“calves”) are spotted
with white till their first change of coat in October. The hind brings
forth one or rarely two calves in May or the beginning of June. The stag
sheds his antlers at the end of February; the new ones are already
full-grown in July. So long as they are growing the stag keeps to the
low woods, and first seeks the high-lying forests when they are
completed. He only leaves the forest for any length of time during the
breeding season, but, wherever possible, comes to the field for a short
time every evening to feed on cabbages, peas, beans, young corn, clover,
lupines, grass, etc. Turnips, carrots, and potatoes, dug out of the
ground by the fore legs, are also devoured. In this way red deer do a
great deal of damage, not only directly in feeding, but also, to a
larger extent, by trampling down the crops. In autumn and winter they
chiefly feed on acorns, beechnuts, buds and young shoots of various
trees. They also peel the bark from young trees, and often cause damage
while rubbing the remains of the velvet from their antlers. Red deer are
injurious to agriculture and forestry. Suitable fencing of fields,
gardens, etc., to be protected.
The =Roebuck= (_Cervus capreolus_) measures up to three and a half feet
long, and about two feet high. Antlers (Fig. 27) only slightly branched,
and rough all over; beams and branches cylindrical. No brow-tynes, and
usually only three branches. Tail extremely small and inconspicuous.
Legs long and slender. Summer coat greyish brown, passing over to a
reddish tint; the longer winter coat brownish grey. A whitish patch on
the rump. The young (“fawns”) have at first white spots on a brownish
ground.
Breeding season in August. The female (“doe”) brings forth her two fawns
in May or June. The roebuck keeps principally to the lower and middle
forests, especially in places where glades, rich in grass and herbage,
and cornfields or meadows alternate with woodland. In the evening it
comes out of the cover to eat in the fields and meadows; towards morning
it withdraws again. The roebuck devours both young corn and corn in the
ear; also ears of millet, beans, peas, clover, and lupines. It does not
appear to touch potatoes and turnips. The bucks in particular do much
mischief by trampling about in cornfields.
The =Fallow Deer= (_Cervus dama_) is about four feet long and three feet
high; antlers rough and cylindrical only towards the root, with
tolerably smooth, flat, shovel-like ends. Old individuals are pale
brown, the summer coat is reddish and brightly spotted; belly whitish; a
white patch on the tail. The young have sharply marked bright spots. In
its habits this non-indigenous species agrees in many respects with the
red deer, but changes its abode less. Towards evening it eagerly leaves
the forest in order to seek its food in the cornfields. As the fallow
deer lives in large herds its trampling does much damage.
ORDER: =Multungula= or =Pachydermata= (MANY-HOOFED OR THICK-SKINNED
MAMMALS).
Non-ruminating hoofed animals with thick, often callous, naked, or
scantily haired, frequently bristly skin and with three to five toes,
which, though they are not all developed to the same extent, are yet
never rudimentary. The various species are very unlike one another as to
food and dentition. Here belong domesticated swine, and a single
species—formerly occurring wild in Britain—
The =Wild Boar= (_Sus scrofa_). On each foot four toes, of which the
two hinder are small and do not usually touch the ground. The wild
boar agrees in the general conformation of its body with the common
domesticated swine. Six incisors in upper and lower jaw; the lower
ones forwardly directed. The canines, which are more developed in
boars than sows, curve outwards and upwards in both jaws as “tusks.”
On each side of each jaw seven tuberculated back teeth completely
covered with enamel. Length of the body 5 feet 10 inches; length of
tail 1 foot 8 inches. Colour: black and rusty brown. The young ones
are white, spotted and striped with dark brown. The wild boar likes
damp, swampy, but at the same time thickly overgrown districts, where
it remains hidden in the day, only seeking the fields and meadows when
it has become dark and quite still. It then chiefly feeds on turnips,
carrots, and potatoes, rooting them out of the ground; it also devours
leguminous crops and grain, but treads down far more of these plants
than it eats. Besides this, it also feeds on acorns, beechnuts,
hazel-nuts, and truffles. The wild boar does some service by devouring
snails, worms, insect larvæ living in the soil, and also the pupæ of
destructive species of caterpillars, which occur in the same
situation; also voles. Thick hedges, in order to protect the corn from
injury.
ORDER: Solidungula (SINGLE-HOOFED MAMMALS),
to which the horse and the ass belong, need not be dealt with here;
still less the other orders enumerated on p. 23.
CLASS II.: =AVES= (BIRDS).
Warm-blooded Vertebrates, which breathe by lungs, are covered with
feathers, have no teeth but a horny beak, and lay hard-shelled eggs,
which are hatched by the warmth of their body. They are adapted for
movement in the air, though not all to the same degree. The fore limbs
are modified into wings, in which, however, the parts found in Mammals
can be recognized. We distinguish in the first place a small thumb, and
then in most cases a two-jointed forefinger and a small second finger.
_Secondary quills_ (Fig. 28, BB) are attached to the ulna, and _primary
quills_ (A, 1–10) to the two metacarpals and the finger joints, while
the thumb bears the bastard wing (C). The tail feathers, or _rectrices_,
are attached to the last joint of the tail. The body is clothed with
stiff, tolerably long _contour feathers_, which conceal the soft short
_down_ from view. The bones are hollow and filled with air. Their
cavities are connected with _air-sacs_, which are found in all parts of
the body, and fill themselves with air from the lungs when the bird
begins to fly. In this way its specific gravity is reduced. The body
firm, especially the hinder part of it, which is almost immovable; the
neck, which may consist of many vertebræ (even as many as twenty-two),
can, on the contrary, be turned in many directions. Birds walk entirely
on their toes; the metatarsals are fused with one of the rows of tarsals
into a “_tarsus_” bone. Tarsus and toes are covered with horny scales.
A bird’s egg (Fig. 29) consists of a germinal disc (_h_) from which the
young bird develops, and which rests on the yolk, made up of substances
serving for the nutriment of the developing bird: the yellow (_a_) and
the white (_b_) yolk, as well as the albumen (_c_, _c_^1, “white of
egg”) in which lie two twisted cords (_chalazæ_),—finally of protective
structures: the shell-membrane (_e_) and the calcareous shell (_f_); _g_
is the air-chamber.
[Illustration:
FIG. 28.—Wing of the Buzzard.
]
[Illustration:
FIG. 29.—A Bird’s Egg.
]
When the young escape from the egg, they are either able to at once look
after themselves more or less, at least to look for their food,—in which
case they can see and are clothed with feathers at hatching (_precocious
young_; _e.g._ fowls, ducks, gulls, and pewits),—or the young remain
some time in the nest, as they are, to begin with, both blind and naked,
and in this case they are fed for some time by the parents (_nestlings_;
_e.g._ birds of prey, sparrows, nightingales, pigeons). In the frigid
and temperate zones most species of birds do not remain in their native
country after the breeding season; those which go south in the autumn
are termed _migrants_; while birds which do not migrate, but remain in
the district where they have bred, are known as _residents_ (sparrow,
jay, magpie). _Gipsy migrants_ execute more or less extensive
wanderings, influenced by want of food or other causes (woodpecker,
titmouse, golden-crested wren, tree-creeper). The travels of such birds
are not, like those of migrants, undertaken at a definite time of year,
or in definite directions (N., S.), but many of their species collect
together in large flocks for the purpose of wandering, like migrants.
The following orders are usually distinguished:
[Illustration:
FIG. 30.—The Eagle Owl (_Otus maximus_).
]
I. _Raptores_ (Birds of Prey), II. _Scansores_ (Climbers), III.
_Passeres_ (Singing Birds), IV. _Gyrantes_ (Doves), V. _Rasores_
(Scratchers), VI. _Grallatores_ (Waders), VII. _Natatores_ (Swimmers),
VIII. _Cursores_ (Running Birds).
The Order Cursores includes the ostrich-like birds, and will not here
receive further notice.
ORDER: Raptores (BIRDS OF PREY).
Upper beak hooked, covered with a skin (_cere_) at its base; four toes
possessing strong claws, and provided with pads in their under side
(Fig. 31); wings powerful. Birds of prey live in pairs, and breed once a
year in nests composed of pieces of wood and branches. The young are
nestlings (p. 51). Sight keen. These birds feed almost exclusively on
vertebrates, principally mammals and birds. An idea of their food can be
gained by examination of their “pellets”—roundish balls composed of the
indigestible parts of their food, and disgorged from twelve to twenty
hours after feeding. Two groups are distinguished—_diurnal_ and
_nocturnal_ birds of prey. The first (Figs. 31, 32) have a laterally
flattened head, eyes directed laterally, and tolerably stiff feathers.
The nocturnal forms (“owls,” Figs. 30, 33) have a large head, flattened
in front, with large eyes facing to the front, soft plumage, and
hair-like feathers on the toes, of which two are directed forwards, one
backwards, and one outwards. The radiating feathers round the eye
constitute a “veil.”
[Illustration:
FIG. 31.—Head and Foot of Falcon.
]
Predominatingly harmful (from killing domestic mammals) are the
following species occurring in Britain: the =Sea Eagle= (_Haliaëtus
albicilla_), the =Golden Eagle= (_Aquila chrysaëtus_), the =Peregrine
Falcon= (_Falco peregrinus_), the =Merlin= (_F. œsalon_), the =Hobby=
(_F. subbuteo_), the =Sparrow Hawk= (_Accipiter nisus_), the =Kite=
(_Milvus regalis_), the =Goshawk= (_Astur palumbarius_), the =Harriers=
(_Circus cyaneus_ and _C. cinerarius_), and the =Honey Buzzard= (_Pernis
apivorus_). The last effects damage by catching honey bees.
[Illustration:
FIG. 32.—The Golden Eagle (_Aquila chrysaëtus_).
]
Useful in the main, being destroyers of field-voles, are the following:
the =Kestrel= (_Falco tinnunculus_), the =Buzzard= (_Buteo vulgaris_),
the =Barn Owl= (_Strix flammea_, Fig. 33), the =Brown Owl= (_S. aluco_),
the =Little Owl= (_Athene noctua_), a casual, the =Short-eared= or
=Woodcock Owl= (_Otus brachyotus_), the =Long-eared Owl= (_O.
vulgaris_), and the =Eagle Owl= (_Otus maximus_, Fig. 30), a rare
visitor.
A bird of prey cannot simply be classed as harmful or useful; a species
mainly injurious may sometimes destroy a field vole or a destructive
bird, while a useful species may sometimes attack domestic poultry.
Game-preserving is destructive of almost all the indigenous diurnal
birds of prey, and of the owls to a less extent.
ORDER: Scansores (CLIMBERS).
Birds with two toes directed forwards and two backwards. The young are
nestlings. Here belong toucans, parrots, cuckoos, and woodpeckers. The
first two groups are limited to the tropics; woodpeckers are only of
importance in the culture of fruit trees and in forestry. I describe
briefly—
[Illustration:
FIG. 33.—The Barn Owl (_Strix flammea_).
]
The =Cuckoo= (_Cuculus canorus_, Fig. 34). Fourteen inches long, tail
eight inches. The yellowish beak is slightly curved; feet yellow. Back
blue-grey in old birds, brownish in young ones. Belly white with dark
transverse lines. Ten tail quills, flecked with white. Shy; flies like a
bird of prey. The female lays her eggs at intervals of about fourteen
days, and cannot therefore hatch them out herself. She lays the egg on
the ground, and then takes it in her bill to the nest of a small bird
which feed its young with insects (wagtail, grasshopper warbler,
nightingale, robin, lesser whitethroat, wren, lark). The cuckoo’s egg is
generally hatched by the foster parent, and the true young often do not
come out from the egg, owing to lack of warmth; or, if hatched, they are
thrown out later on by the much larger, rapidly developing young cuckoo.
Every cuckoo, therefore, is so far harmful that it costs the lives of
several insect-eating birds. But it far more than compensates for this
by destroying insects. It is especially beneficial to fruit-tree culture
and forestry, since it eats an enormous number of caterpillars; but in
late summer it comes frequently from the woodland into the fields, and
then eats the caterpillars of the cabbage white, cabbage moth, and
silver Y moth, surface caterpillars, and the larvæ of the turnip
saw-fly. It also devours mole-crickets and (naturally in the spring)
cockchafers.
[Illustration:
FIG. 34.—The Cuckoo (_Cuculus canorus_).
]
ORDER: Passeres (PERCHING BIRDS).
This order is essentially constituted by all those birds with helpless
young (p. 51), which do not belong to the two preceding orders or the
one next following. Beak without a cere. Three toes forwardly, one
backwardly directed.
Group: =Hirundinidæ= (_Swallows_).
With short flat beak, broad at the base, with gape extending far back,
and triangular as seen from above. In flight the beak is opened as
widely as possible, serving for catching insects. Wings long and
pointed. Feet short and weak, entirely unsuited or only poorly adapted
for walking; their chief use is to enable the swallow to hold fast to
different objects. Swallows fly quickly and catch insects while on the
wing. The insects on which they prey are generally unimportant to
agriculture and forestry; but they may also do good by catching crane
flies (_Tipula_), and ribbon-footed corn flies (_Chlorops_), which often
fly about our fields in enormous swarms in order to lay their eggs. All
swallows are migratory birds. There belong here—
1. True =Swallows= (_Hirundo_), with forked tails; three toes directed
to the front, one to the back. Here may be reckoned—=Swallow= (_H.
rustica_), always broods in sheltered spots, _e.g._ inside a stable,
summer-house, or verandah; =House Martin= (_H. urbica_), nests against
buildings, under the eaves for example; the =Sand Martin= (_H.
riparia_), breeds in the neighbourhood of streams, especially in
vertical banks of loamy or coherent sandy soil, where it makes its nest
at the end of a passage a yard long. The =House Martin= is shining black
on the back, white on the entire under surface and rump. The =Bank
Martin= is brownish grey on the back, white on the under side, with
brownish-grey bands on the breast.
2. =Swifts= (_Cypselus_), with forked tails and four strong, curved,
forwardly directed claws. Only one British species belongs here—the
=Swift= (_Cypselus apus_), ten inches long, brownish black except for
white throat, and with very long curved wings.
3. =Night-jars= (_Caprimulgus_), with tail not forked, soft plumage,
large head and eyes; fly at night. One species belongs here—the
=Goatsucker= (_Caprimulgus europæus_, Fig. 35), twelve inches long, grey
on the upper side, spotted with blackish brown and rusty yellow,
yellowish whitey grey with dark wavy lines on the under side. In the day
it flies awkwardly and heavily, and usually keeps under cover; by night
it flies rapidly and boldly, especially in bare spots in woods, or in
gardens and on fields. It haunts especially the neighbourhood of
sheepfolds and cattle in the meadows, since it always finds flies and
gnats there. It also catches cockchafers and various moths.
[Illustration:
FIG. 35.—The Goatsucker (_Caprimulgus europæus_).
]
Group: =Magnirostres= (_Large-beaked Perching Birds_).
Beak strong, thick, often incurved near its apex. These birds eat almost
all kinds of food, both animal and vegetable. Here belong Starlings and
Raven-like Birds (crows, magpies, jays).
The =Starling= (_Sturnus vulgaris_).
Plumage black, with a violet sheen. The tips of the contour feathers,
however, are white or bright yellowish. These white patches become so
well marked after the autumn moult, that they almost completely cover
the shining metallic black of the feathers. They gradually become
smaller; in the next spring they are almost or entirely lost. Very
serviceable. Devours, especially in autumn, many field snails, also
cockchafer grubs, wireworms, grass caterpillars, grasshoppers,
leaf-lice; also many insects destructive to fruit trees and forest
trees. The starling, however, is able to do considerable damage to
garden fruit trees, since it eats cherries, currants, and sometimes even
pears. Starlings often settle on the backs of sheep and cows in order to
pick off the vermin.
Genus: =Corvus= (_Crow-like Birds_).
Here belong—1. The =Jackdaw= (_C. monedula_), with relatively short beak
and long tarsi. Black; side of the head and neck ashen grey. Breeds in
holes in trees, chimneys, ruins, and towers. 2. The =Hooded Crow= (_G.
cornix_); bright grey, except the head, throat, wings, and tail, which
are black. Breeds in all parts of Europe east of the Elbe; occurs in
Western Europe as a gipsy migrant in winter. 3. =Carrion Crow= (_C.
corone_); black, beak stout and strongly bent at its end. Breeds in
trees, but never (like the Rook) in large numbers together. 4. =Rook=
(_C. frugilegus_); black, beak rather long; in adult specimens the head
feathers are quite worn away at the base of the beak. 5. =Raven= (_C.
corax_); much larger than the other species; black, beak very strong,
strongly curved along its entire upper side. Nowhere in large numbers.
[Illustration:
FIG. 36.—Head of Rook (_Corvus frugilegus_).
]
_Food, Benefit conferred, and Damage done._ Ravens, and sometimes even
rooks, attack lambs and sick sheep, also ducks, geese, fowls, and
pigeons. Carrion crows and hooded crows rarely attack our domestic
animals. All crows, however, steal the eggs of our poultry. They also
injure sport, since they kill hares and rabbits, young fawns, quails,
pheasants, etc. They do a little good, however, by devouring
field-voles, but, as a rule, only catch the sick ones which are not able
to move quickly. They do harm by destroying useful insect-eating birds,
also eating their eggs and young. But as insect-eaters, they are
extremely useful; they devour cockchafers, wireworms, butterflies,
surface caterpillars, crane flies and their larvæ, and field snails;
also many earthworms. As to the vegetable part of their food, they
devour, in the first place, germinating seeds; grain, peas, beans. They
also pick grain from the ear, both when ripe and, to a larger extent,
when still soft; and in doing this pull down the ear so as to crack the
stalk, thus causing more damage than by the mere eating. They also
plunder the ripening peas, and feast upon cherries, plums, apricots, and
other juicy fruits; even potatoes and turnips. All crow-like birds do
some harm and some good, only the raven (which eats scarcely any
insects) is to be always reckoned as an enemy.
The =Magpie= (_Pica caudata_) and =Jay= (_Garrulus glandarius_) are
resident birds closely related to the crows. The first affects open
tracts of land (fields, meadows, gardens) in the neighbourhood of large
trees; the latter is a woodland bird. Both birds eat almost everything:
grain, acorns, beechnuts, cherries, berries; cockchafers, wireworms, and
similar insects; the eggs and young of useful insect-eating song-birds
(such as titmice), also these little birds themselves, ducklings and
chickens, young partridges, quails, pheasants, now and then field-voles.
More harmful than useful.
Group: =Conirostres= (_Conical_-_beaked Perching Birds_).
Beak conical, thicker and shorter than in the species of the following
group. They devour insects and seeds, a few species seeds exclusively.
Here belong first the =Titmice= (_Parus_), gipsy migrants which are
extremely serviceable both in fruit-tree culture and forestry. Then the
=Larks= (especially the =Skylark=, _Alauda arvensis_, a resident), which
nest on the ground, eating insects, seeds, and in winter even leaves;
they feed their young, however, with insects. They do both good and
harm, but the former mostly preponderates. In late summer and autumn,
skylarks collect in flocks, and wander here and there for a long time:
before this, they travel south; at this time many are caught and eaten.
The male skylark sings beautifully, rising meanwhile high in the air.
The =Buntings= (_Emberiza_) have a characteristic compressed and pointed
beak; they seek their food on the ground in fields and meadows, and on
roads. The food consists of grain and insects; but since these birds
never take grains from the ear, they only do damage by picking them up
at seed-time. They feed their young with insects. The damage is usually
very inconsiderable, but, on the other hand, the benefit conferred is
slight. (=Yellow Hammer=, _E. citrinella_, a yellow-coloured resident.
The =Common Bunting=, _E. miliaria_, a grey-coloured migrant, etc.) In
the family of =Finches= a number of species are included which are of
small agricultural importance: _e.g._ the =Bullfinch= (_Pyrrhula
vulgaris_), specially attacks fruit-tree buds in March; the =Goldfinch=
(_Carduelis elegans_); the =Siskin= (_Chrysomitris spinus_); the =Lesser
Redpoll= (_Linota linaria_); the =Greenfinch= (_Ligurinus chloris_). A
few species, however, must be dealt with more fully, and, first,—
[Illustration:
FIG. 37.—Head of Bullfinch.
]
The two =Sparrows=,
_i.e._ the =House Sparrow= (_Passer domestica_) and the =Tree Sparrow=
(_P. montana_).
=House Sparrow=: ear region bright grey. A rust-coloured or yellowish
streak behind the eye. The whole throat black in the male. Wings with a
yellowish white transverse band. =Tree Sparrow=: ear region black. A
black streak behind the eye, a white band round the neck, and a black
patch on the throat. Wings with two white transverse bands. The two
sparrows are very much alike in their habits, but the house sparrow
frequents more the neighbourhood of human dwellings, even in large
towns. Both sparrows are mainly harmful; where seeds (especially those
containing starch, _e.g._ corn) are available, they prefer this kind of
food to any other; and, besides this, they chiefly bring up their young
on soft unripe grain. Sparrows devour the germinating corn after
seed-time, and also pick the grain from the ear, in which process they
at the same time do damage by breaking down the haulms so that the grain
falls out. They pick the young peas from their pods; devour, too,
several juicy tree fruits, _e.g._ cherries and grapes; and destroy young
garden seedlings, _e.g._ lettuce, spinach, garden flowers. The house
sparrow eats more insects than the tree sparrow (among them—geometer
caterpillars, injurious roller caterpillars), but leaves the most
noxious kinds untouched. Both sparrows are residents, but in autumn and
winter often collect together in large flocks.
The =Linnet= (_Linota cannabina_),
with grey-brown darkly spotted back. Belly whitish, tail black with
broad white margins. During summer the top of the head and the breast of
the male are of a beautiful red. They are often found together in flocks
during September. In spring and summer they chiefly live on
oil-containing seeds, and may even do some good by eating the seeds of
charlock; usually, however, doing much more harm by devouring the seed
of rape, flax, linseed, and hemp.
The =Chaffinch= (_Fringilla cœlebs_).
A white patch on the two outermost tail feathers and the ones next them.
Wings with one white and one yellowish transverse band. Male: upper side
of head and neck bluish grey, back brown, breast reddish brown. Female:
back grey-brown, belly whitish, breast ash-grey. The chaffinch inhabits
forests, both those of ordinary foliage trees and those consisting of
conifers; it also nests in gardens and plantations. At the beginning of
September the males separate from the females, and both sexes collect in
large flocks which haunt gardens, avenues, and bushes. In mild winters
they remain resident, but travel away if the cold is greater. The
chaffinch devours oil-containing seeds by preference, but also eats
starchy ones, and seeks its food on the ground. It does a great deal of
damage in cornfields by picking the seeds out of the soil after they
have been sown; but does not take the grain from the ear. It also eats
young seedlings. But valuable services more than counterbalance the harm
done. When the chaffinches in autumn fly about in large flocks in the
fields, they eat an enormous number of weed seeds. The young are chiefly
fed with insects, especially with caterpillars. In the spring, when the
seeds have germinated and the young corn is not yet ripe, the chaffinch
feeds itself also on insects.
Group: =Subulirostres= (_Awl-beaked Perching Birds_).
Beak slender, awl-shaped, round in transverse section. A fully developed
organ of voice. Feed almost exclusively on insects; there are only a few
species which occasionally eat seeds. A few of them, however, sometimes
devour juicy fruits (cherries, bird-cherries, elder-berries,
juniper-berries, grapes). The birds belonging to this group, without
exception, feed their young on insects. They are of service; even those
species which occasionally do damage are useful on the whole.
There belong to the Subulirostres—
The =Wagtails= (_Motacilla_), _e.g._ the =White Wagtail= (_M. alba_),
usually living in the neighbourhood of water, and seeking its insect
food in the fields (often behind the plough), and in pastures and
gardens.
The lark-coloured =Pipits= (_Anthus_).
The =Hedge Accentor=, or “Sparrow” (_Accentor modularis_),—in garden
hedges, and woods, feeding sometimes on seeds.
The following “warblers:” =Nightingale= (_Daulias luscinia_), =Robin=
(_Erithacus rubecula_), =Redstart= (_Ruticilla phœnicurus_), the =Lesser
Whitethroat= (_Sylvia curruca_), =Garden Warbler= (_S. hortensis_),
=Willow Wren= (_S. trochilus_), =Chiffchaff= (_S. rufa_), =Reed
Warblers= (_Acrocephalus streperus_ and _A. arundinacea_), etc. The
last-named live among reeds and rushes on the banks of fresh waters, and
eat insects which do not affect agriculture and forestry; all the other
warblers are useful.
Other examples of the Subulirostres are the =Golden-crested Wren=
(_Regulus cristatus_), and the =Common Wren= (_Troglodytes parvulus_),
which are of service to forestry and fruit-tree culture, but not to
agriculture.
[Illustration:
FIG. 38.—The Nightingale (_Daulias luscinia_).
]
Most of the native thrush-like birds (_Turdus_), _e.g._ the =Blackbird=
(_T. merula_), the =Missel Thrush= (_T. viscivorus_), the =Fieldfare=
(_T. pilaris_), the =Redwing= (_T. iliacus_), and the =Song Thrush= (_T.
musicus_), assist the farmer by devouring noxious insects and snails;
but several of them occasionally do damage by poaching on cherries,
grapes, currants, etc. Some of them (_e.g._ the Song Thrush and
Blackbird) breed in almost all parts of Britain, others come here only
in autumn or winter.
ORDER: =Gyrantes= (DOVES).
Body strongly built, somewhat thick-set. Wings long and pointed. Beak
weak, with a cere at its base; nostrils covered by gristly scales. Toes:
three forwardly and one backwardly directed, free, _i.e._ without a web
(as in poultry). The young are at first blind and naked. They are at
first fed with a cheesy secretion of the glands of the crop; later, with
grain softened in the crop. Doves always live in pairs. Nests careless,
flat, of loosely arranged twigs; situated on tree-branches, rocks, and
large buildings. Doves breed twice or thrice a year, laying two longish,
shining white eggs.
Native British forms:—
[Illustration:
FIG. 39.—The Wood Pigeon (_Columba palumbus_).
]
1. =Wood Pigeon= (_Columba palumbus_, Fig. 39), from April to September
scattered about in the woods, but after the breeding season wander about
in flocks, and in winter travel further south, although many remain. It
nests on horizontal branches, and feeds on seeds of fir and pine,
acorns, beechnuts, also grain, peas, vetches, rape-seed,—but seeds of
many weeds as well (_e.g._ those of charlock, vetchling, spurry,
cleavers). When the earth is covered with snow it often eats cabbage and
the leaves of winter rape, but is also of some service.
2. The =Turtle Dove= (_C. turtur_) occurs on the edges of woods,
especially those consisting of coniferous trees. Nests in the trees. For
_food_, _use_, and _harm_, cp. the preceding species. Steals buckwheat
grains from the fields.
3. The =Rock Pigeon= (_C. livia_) is the original stock of our races of
domestic pigeons. It nests, as a resident, in the Mediterranean
countries; as a migrant, on the rocky parts of the coasts of Great
Britain and the Orkneys, Shetlands, and Faroe Islands.
ORDER: =Rasores= (POULTRY).
Body strong, thick-set. Head small, often with naked, brightly coloured
patches, with fleshy combs or with a crest of feathers. Tip of the upper
beak bends over that of the lower one. No cere (cp. Doves). Wings short,
rounded; flight heavy. Feet strong. Hinder toe small and usually
attached to the tarsus higher up than the front toes. Claws blunt. A
small web at the bases of the toes. The male of several species bears a
spur on the tarsus. Birds of this order usually keep on the ground,
scraping it in search of their food, which consists of seeds, berries,
the green parts of plants, insects, worms, and snails. Young precocious
(p. 51). Several domestic birds belong to the Rasores: pheasants, the
various races of fowls, pea-fowls, guinea-fowls, turkeys.
The species living wild in Britain are game-birds. They are—the
=Capercailzie= (_Tetrao urogallus_, Fig. 40), =Black Game= (_T.
tetrix_), =Partridge= (_Perdix cinerea_), =Quail= (_P. coturnix_); none
of them are particularly harmful or useful to agriculture.
The =Pheasant= (_Phasianus colchicus_, Fig. 41) was originally a native
of the Caucasus, and shores of the Caspian Sea and Sea of Aral; it
occurs wild in Central Europe. Pheasants are troublesome to the farmer,
both by devouring the newly sown seed and by scratching up the fields.
[Illustration:
FIG. 40.—Male and Female Capercailzie (_Tetrao urogallus_).
]
ORDER: =Grallatores= (WADING-BIRDS).
The species here included differ very much among themselves; but all
seek their food, which is almost exclusively of animal nature, at the
water-edge (rivers, brooks, lakes, ditches, canals, seashore) or in damp
places (damp meadows and ploughed fields, moors, swamps). They are,
therefore, adapted to wading, and for this purpose have a long
featherless tarsus, while the lower half of the long shank is quite bare
and covered with horny scales. In flight the wading-birds do not draw
their legs up to their body, as is the case with the birds already
spoken of, but stretch them out behind to their full length. Monogamous.
Young precocious (p. 51), except in storks and herons when they are
nestlings. The shore-dwellers eat fish, bivalve molluscs, etc.; only
those species living on damp meadows and fields are of use to
agriculturists, by devouring insects, snails, and worms. These are
indicated by the letter u in the following list of the commonest native
kinds:—
[Illustration:
FIG. 41.—The Pheasant (_Phasianus colchicus_).
]
=Coot= (_Fulica atra_); =Water Hen= (_Gallinula chloropus_); =Corn
Crake= (_Crex pratensis_, u); =Plovers= (_Charadrius_, u); =Pewit= or
=Lapwing= (_Vanellus cristatus_, u); the =Snipes= (_Scolopax_); the
=Curlews= (_Numenius_, u); the =Stints= (_Tringa_); the =Godwit=
(_Limosa ægocephala_, u); the =Sandpipers= (_Totanus_, u); the =Heron=
(_Ardea cinerea_).
[Illustration:
FIG. 42.—The Woodcock (_Scolopax rusticola_).
]
ORDER: =Natatores= (SWIMMING-BIRDS).
These birds are distinguished by their swimming powers and corresponding
organization. Legs usually set on far back, shorter than the body. The
feet in particular are adapted for swimming. In some swimming-birds each
of the forwardly directed toes has a webbed margin (“split swimming
feet,” Fig. 43); in others, the three front toes are all united by a web
(Fig. 44), while the hind toe is either small or wanting (“swimming
feet”); lastly, there are some in which all the toes are forwardly
directed and united by a common web (“oar-feet”). The plumage of
swimming-birds is compact, and always kept greasy by the secretion of
the oil-gland. I shall speak of two families only.
Family: =Lamellirostra= (_Ducks_).
[Illustration:
FIG. 43.—Crested and Little Grebes (_Podiceps cristatus_ and _minor_).
]
The inner margin of the beak is covered by skin, thrown into transverse
ridges or tooth-like projections. Swimming feet (Fig. 44). Tolerably
long wings; remarkable powers of flight. Feathers soft. These birds
mostly affect shallow fresh water, in which they get their food by
grubbing in the mud, the soft skin of the beak serving as an organ of
touch. Polygamous. Young precocious (p. 51).
Here belong—the long-necked =Swans= (_Cygnus_) and the thick
short-necked =Geese= (_Anser_), in which the beak is higher than broad
at its base; the =Swimming Ducks= (_Anas_) with broader beaks, the
=Diving Ducks= (_Fuligula_), and =Goosanders= (_Mergus_) with a broad
hanging web to the hind toe. None of these birds are useful, while wild
geese and ducks are harmful.
[Illustration:
FIG. 44.—Goose (_Anser cinereus_).
]
Three species of wild =Geese= (=Grey Goose= = _Anser cinereus_, =Bean
Goose= = _A. segetum_, =White-fronted Goose= = _A. albifrons_) chiefly
breed in Eastern or Northern Europe, and only come to Britain in autumn
or winter, flying about in flocks. They eat the grass in low-lying
meadows, and even pull it up by the roots; in the cultivated fields they
devour winter corn and winter rape, and tread down more with their
clumsy feet than they eat. They are also harmful to vegetable growth,
owing to the very caustic nature of their dung, which is often deposited
in large quantities in one place. In regions where they breed they also
devour both ripe and unripe grain. Where they only occur in autumn, they
scrape potatoes, turnips, and carrots out of the ground in order to eat
them. Flocks of geese fly in a slanting line or in the form of a
ploughshare.
Among _Swimming Ducks_ damage is only done by the =Wild Duck= (_Anas
boschas_). It breeds wherever there are fresh waters. Nests amongst
grasses or swamp-plants, or in a tree. The wild ducks remain the whole
winter as long as the waters are not frozen, otherwise they go off for a
short time to the south. Food: the tops of stems, buds, leaves of
various water-plants, also barley, oats, and other grain; water-insects,
fish, and fish-spawn. These ducks also do damage in cornfields by
treading down and cracking the plants.
Family: =Longipennes= (_Gulls_).
Usually swimming feet. Legs tolerably long, adapted for wading (Fig.
45). Wings long, pointed. Beak laterally compressed. Young nestlings (p.
51). Breed in larger or smaller flocks, usually on the coast,
occasionally on the margin of fresh waters. They chiefly feed on fish,
worms, molluscs, and crustacea; sometimes, in the case of a few species,
on young birds and eggs, as well as mice and other small mammals. Gulls
are usually of no importance in agriculture; but the =Black-headed Gull=
(_Larus ridibundus_), which breeds on the banks of lakes and rivers,
devours many cockchafers and other noxious insects. The =Herring Gull=
(Fig. 45), =Kittiwake= (_Larus argentatus_ and _L. tridactylus_), and a
few other species, which breed on the coast, sometimes show themselves
inland, especially in stormy weather; they then pursue field-voles, and
catch many injurious insects.
Besides the true =Gulls= (_Larus_), I will only mention the =Sea
Swallows= (_Sterna_), with forked tails.
[Illustration:
FIG. 45.—Herring Gull (_Larus argentatus_).
]
CLASS III.: =REPTILIA= (REPTILES).
Cold-blooded Vertebrates (p. 19). The heart has the same structure as in
Mammals and Birds, but the left and right ventricles are usually only
incompletely divided from one another (p. 20). The body is invested with
horny scales or with bony plates covered by a horny layer. Reptiles are
very unlike Birds in appearance, but present many essential points of
resemblance to them in their skeleton; indeed, during earlier geological
times, there were transitional forms between the two classes. The
structure of the reptile egg, too, is very similar to that of the bird’s
egg; but the first has no lime-salts deposited in its shell. The egg is
not hatched out by the animal itself, but exposed to the heat of the sun
or to the warmth developed by decaying vegetable matter. Several
reptiles (adder, for example) keep their eggs in their bodies till the
young escape. Reptiles have either no limbs (snakes, a few lizards), or,
at any rate, the limbs are not well developed, and are so placed that
the body does not rest upon them, but is slung between them.
[Illustration:
FIG. 46.—Common Lizard (_Lacerta agilis_); 2, head of the same from
below; 3, tongue.
]
The Reptilia are divided into the Orders of =Crocodilia= (Crocodiles),
=Chelonia= (Turtles and Tortoises), =Lacertilia= (Lizards), =Ophidia=
(Snakes).
[Illustration:
FIG. 47.—The Adder (_Pelias berus_).
]
Our native reptiles have no agricultural importance. I will, however,
briefly mention the =Adder= (_Pelias berus_, Fig. 47), as it is
dangerous to man. Head broad; tail much smaller than the hinder end of
the body. Colour greenish grey or brownish. A black zigzag band runs
along the dorsal side of the body. Length about twenty inches. The two
hook-shaped poison-fangs are found in the front of the upper jaw;
opening the mouth widely causes them to be erected. They are traversed
by poison-canals through which the poison flows immediately into the two
bloodless wounds. The adder lives in woods and on mountain slopes, where
it devours mice. The poison has a decomposing action on the blood; it
causes fever, and swelling of the part bitten, as well as sometimes of
the neighbouring parts. The bite may be fatal. Alcohol is spoken of very
highly as a remedy.
[Illustration:
FIG. 48.—The Grass Snake (_Tropidonotus natrix_).
]
[Illustration:
FIG. 49.—Blindworm (_Anguis fragilis_).
]
The native =Ringed Snake= (_Tropidonotus natrix_, Fig. 48), three feet
long, is bluish with belly flecked with black and white; a yellow and a
black band on the neck. It is fond of going into the water, and eats
frogs, newts, and insects. The =Smooth Snake= (_Coronella lævis_), two
feet long, is brown, with black patches on the back, which, however, do
not form a continuous band. Head dark velvety black. Devours lizards and
blindworms. The =Blindworm= (_Anguis fragilis_) is indeed snake-like, or
rather worm-like (Fig. 49), but nevertheless belongs to the lizards,
with which its internal structure agrees.
CLASS IV.: =AMPHIBIA= (AMPHIBIANS).
[Illustration:
FIG. 50.—Great Crested Newt (_Triton cristatus_); male above, female
below.
]
Cold-blooded Vertebrates (p. 19). The heart has only one ventricle and
two auricles (cp. p. 21). The skin is naked, damp, usually slippery and
smooth; it helps in respiration. Although several Amphibians resemble
various Reptiles in outward appearance (Newt and Lizard, Figs. 50 and
46), the structure of the skeleton is quite different. Upon the whole,
Amphibians resemble fishes more closely, and they breathe by gills when
they are young, which strengthens the agreement. They undergo a
metamorphosis. The just-hatched young at first hold fast by suction to
the jelly of the spawn; they have external gills. They quickly develop a
membranous margin to the body, especially round the tail, which
consequently forms a sort of oar. Meanwhile internal gills develop, and
the external ones disappear. The larvæ are now fish-like (“tadpoles”).
The limbs quickly grow out, the lungs develop, the tail shrivels up, and
the animal leaves the water. Even the adult, however, lives among damp
surroundings. In the adult state the Amphibians feed on insects, worms,
and snails; many species are exceedingly useful owing to this.
Amphibians are divided into two orders, the _Urodela_ (Newts, etc.) and
the _Anura_ (Frogs and Toads). To the first belong the =Great Crested
Newt= (_Triton cristatus_) and the =Common Newt= (_Lissotriton
tæniatus_). Examples of the Anura are the =Edible Frog= (_Rana
esculenta_), the brownish =Common Frog= (_R. temporaria_, Fig. 51), the
=Common Toad= (_Bufo vulgaris_), and the =Natterjack= (_B. calamita_,
Fig. 52).
[Illustration:
FIG. 51.—Common Frog (_Rana temporaria_).
]
Both frogs and toads do good by devouring many noxious insects, and
also, in particular, snails. Toads are often kept in greenhouses for
this purpose; and in the research garden attached to the Rouen
entomological laboratory the snails were entirely exterminated in 1891,
as a result of introducing a hundred toads and ninety frogs.
[Illustration:
FIG. 52.—Natterjack (_Bufo calamita_).
]
CLASS V.: =PISCES= (FISHES).
Cold-blooded Vertebrates (p. 19), which breathe by gills during their
whole life. The heart consists only of a single ventricle and a single
auricle (p. 18). The head passes immediately into the body without any
intervening neck. Fishes move chiefly by means of the tail, at the end
of which there is a tail-fin. This and the dorsal and anal fins lie in
the median plane of the fish, while the pectoral fins, which are
attached to the skull in bony fishes, and also the ventral fins, are
paired structures more or less comparable to the fore and hind limbs of
higher vertebrates. The skeleton of most fishes (pike, perch, carp, eel,
plaice) is bony; but in a few subdivisions of fishes (sharks, skates,
sturgeons, lampreys) it is cartilaginous. The skin is usually covered
with thin translucent scales; but there are fishes with a smooth skin
(lampreys), with prickle-like dermal ossifications (sharks), and with
rhomboidal bony plates (sturgeons). As Fishes are without exception
aquatic, there is no need for me to treat more specially of them here.
[Illustration:
FIG. 53.—The Perch (_Perca fluviatilis_).
]
Second Sub-Kingdom: ARTHROPODA (JOINTED-LIMBED ANIMALS).
[Illustration:
FIG. 54.—Wood-borer (_Sirex_); 1, larva; 2, adult insect.
]
[Illustration:
FIG. 55.—The Large Centipede (_Scolopendra morsitans_).
]
[Illustration:
FIG. 56.—Ground Beetle, with nervous system drawn in white.
]
The body of an Arthropod is bilaterally symmetrical (cp. p. 16), and
consists of a number of joints (Fig. 55), not equally numerous in all
members of the sub-kingdom. These joints or segments lie one behind the
other, and are at first alike; but as in the course of further
development they become adapted to various functions, the difference
between them becomes greater. Compare the Wood-borer represented in Fig.
54, 2, with the young form of the same animal (Fig. 54, 1). The segments
often fuse together, which brings about the formation of a smaller
number of subdivisions to the body; or even all the segments may become
united (mites). In the last case the Arthropod characters are only to be
seen in the jointing of the limbs. Segmented animals (_e.g._ the common
earthworm) are also found among the worms (Sub-kingdom III. of the
Animal Kingdom); but these worms have either no limbs, or only small
unjointed foot-stumps, never jointed limbs as in the Arthropods. These
last are limbless or with unjointed foot-stumps only when young; when
adult they always have jointed limbs. The head of Arthropods bears
several successive pairs of jaws, which move to and fro from one side
towards the other. The covering of the body consists of hard protective
pieces; it is only in the young condition that the skin of several
species is soft. Arthropods have no internal skeleton; the muscles are
attached to the skin. The central part of the nervous system (p. 10),
which consists in Vertebrates of brain and spinal cord, lies in
Arthropods almost entirely on the ventral side. In the head is situated
the cerebral ganglion, a large nervous mass resting on the gullet, and
giving off nerves to the eyes and feelers. Besides this, there is a
ventral nervecord on the ventral side of the animal, running below the
gut, and made up of several pairs of ganglia, united with one another by
means of nerve fibres. The ganglia of the ventral cord send their nerves
to the jaws, limbs, muscles, viscera, etc. The cerebral ganglion is
connected with the first ventral ganglion by means of a cord on each
side of the gullet (Fig. 56), so that a ring-like structure is formed.
The breathing organs are gills in some Arthropods (the Crustacea, _e.g._
crayfish, crabs); insects and centipedes breathe by air-tubes or
tracheæ, while the respiratory organs of spider-like animals, when these
do not breathe entirely by means of the skin, are more or less strongly
modified tracheæ. The structure of the tracheal system is generally as
follows: on each side of the body there is a row of breathing-holes, or
stigmata, through which the air can enter the tracheæ; these are very
much branched, so that they finally become very fine tubes investing the
various organs, which in this way obtain the requisite amount of oxygen.
The stigmata on one side of a caterpillar are clearly shown in Fig. 60,
and those of a hornet larva in Fig. 61.
Four classes belong to this sub-kingdom: Insecta (Insects), Myriapoda
(centipedes, etc.), Arachnoidea (spiders, scorpions, etc.), Crustacea
(crayfish, crabs, lobsters, etc.).
CLASS I.: =INSECTA= (INSECTS).
[Illustration:
FIG. 57.—A Grasshopper, with the different regions of the body
separated from one another. A, head; B, thorax: _I._, prothorax;
_II._, mesothorax; _III._, metathorax; C, abdomen; _a_, antennæ;
_b_, eyes; _c_, _d_, _e_, legs; _f_, _g_, wings; _p_, shank; _q_,
foot.
]
Breathe by tracheæ (cp. p. 84). The segments fuse into three body
regions (Fig. 57). These are—(1) the _Head_, bearing the eyes, feelers
(antennæ), and jaws; (2) the _Thorax_, composed of three fused segments,
of which the first (prothorax) bears a pair of legs, while the second
(mesothorax) and third (metathorax) not only bear a pair of legs each,
but also sometimes a pair of wings in addition; (3) the _Abdomen_, which
possesses no limbs, and of which the number of segments is not always
the same. These three regions of the body perform different functions;
the head is concerned with sensation and the taking up of food, the
thorax with movement, while the abdomen contains the organs of digestion
and reproduction. I will now deal somewhat more fully with the different
body regions of an insect.
_Head._—Almost all insects have in the adult state a compound eye,
_i.e._ an eye made up of a large number (up to ten thousand) of smaller
eyes. In many insects one finds in addition to this a few simple eyes on
the top of the head. The feelers are very unlike in different insects;
they serve as organs of touch, and perhaps also help some other sense.
The mouth-parts consist of three pairs of jaws, of which the first (the
mandibles) and the second pair (maxillæ) are freely movable from side to
side, while the third consists of two jaws immovably fused together
(lower lip, or labium). A downward projection of the skin of the head
(the upper lip, or labrum) overhangs the three pairs of jaws (Fig. 58).
In insects which feed on solid matters, tearing or chewing them, the
jaws are short and sharp-edged (biting mouth-parts); in those which take
up fluid food (blood, the juices of plants, etc.) they are elongated,
and adapted for licking, sucking, or piercing.
[Illustration:
FIG. 58.—Head and Mouth-parts of a Ground Beetle, enlarged four times.
A, from above; B, from below. _a_, labrum; _b_, mandible; _f_,
maxilla with palpi (_g_); _c_, labium with palp (_e_).
]
_Thorax._—The names of the parts of the legs are for the most part those
used in the case of mammalian limbs; though the similarity between the
limbs of Mammals and Insects is quite superficial. The following parts
are distinguished in the leg of an insect: (1) the generally spherical
hip (_coxa_) (Fig. 59, _a_); (2) the very short _trochanter_ (_b_); (3)
the elongated thigh (_femur_) (_c_); (4) the shank (_tibia_) provided
with movable spines at its tip (_d_); (5) the three- to five-jointed
foot (_tarsus_) (_e_), whose last joint ends in claws, and often also in
flap-like outgrowths. The _Wings_ are expansions of the skin, which
consist of two layers. There are tracheæ between the upper and lower
lamellæ. At first (in the pupa) the wings are folded up; but the forcing
of air into the tracheæ quickly causes them to unfold. A firm substance
is now deposited in the larger tracheæ, which are thus converted into
veins or ribs giving support to the wings. In beetles the fore wings are
quite hard and horny, and serve for protecting the delicate hind wings
and soft back rather than for flight; they are therefore named
“wing-covers” (_elytra_). In many insects the fore wings (wasps) or the
hind wings (beetles, grasshoppers) are folded when at rest.
[Illustration:
FIG. 59.—Leg of a Ground Beetle (× 2).
]
[Illustration:
FIG. 60.—Silkworm Moth (_Bombyx mori_). Female moth, caterpillar, pupa
and cocoon.
]
The _abdomen_ only bears organs of movement in caterpillars (Fig. 60)
and a few other insects in the young condition, and in these cases they
are not jointed like the true legs or “thoracic feet,” but unjointed
pro-legs or “abdominal feet.” In the adult insect the abdomen may have
thread-like (mole-cricket) or pincer-like (earwig) appendages; or
appendages used in egg-laying (ovipositors, _e.g._ Locust).
Most insects have great powers of reproduction. A few bring forth living
young, but most insects lay eggs. It is only in a few (_e.g._ lice) that
animals exactly like their parents are hatched from the eggs; the large
majority of insects pass through a _change_, or _metamorphosis_.
A distinction is drawn between _complete_ and _incomplete_
metamorphosis. It is said to be complete when the insect passes through
a stage in which it takes up no food, and, as a rule, moves but little.
In this condition of almost complete rest the insect is called a “pupa”
(Figs. 60, 61, 65). The metamorphosis is called incomplete when the
insect does not pass through a pupa stage, and therefore feeds and moves
during all the periods of its development, merely altering its form
somewhat during its various moults (Fig. 62).
[Illustration:
FIG. 61.—The Hornet (_Vespa crabro_), with larva and pupa.
]
The word “moult” must here be explained. The covering of the skin of
Arthropods consists of hard parts incapable of being stretched. At the
end of a definite period of time this firm covering is stripped off and
replaced by a new investment, soft at first, but afterwards becoming
hard. In this way growth can be effected in spite of the hard
integument. Everyone must have noticed at some time or other the
moulting of caterpillars.
[Illustration:
FIG. 62.—The Migratory Grasshopper (_Acrydium migratorium_). Larva and
adult female.
]
[Illustration:
FIG. 63.—Looper Caterpillar.
]
[Illustration:
FIG. 64.—False Caterpillar.
]
In insects with incomplete metamorphosis the form of the animal alters a
little at every moult, becoming more and more like that of the adult
insect. In the last moult but one small imperfect wings appear (Fig. 62,
_left_), and fully developed wings are only present after the last
moult. The ovipositors of female insects, in those cases where the
metamorphosis is incomplete, first appear as fully developed organs in
the perfect condition of the animal, but begin to develop in the
preceding stage. In cases of this kind of metamorphosis the young insect
(“larva”) closely resembles the adult in form even in the first stage of
development. In insects undergoing complete metamorphosis the difference
between larva and adult insect (imago) is much greater (Figs. 60, 61,
65).
[Illustration:
FIG. 65.—The Common Cockchafer (_Melolontha vulgaris_). Larva, pupa,
female flying, and male creeping out of the earth.
]
The time passed in the pupa state by insects with complete metamorphosis
is by no means always of the same length. For example, there are two
generations annually of the cabbage white butterfly; one lives through
the winter in the pupa state, the pupæ of the other are found in summer.
So that while an insect of the winter generation lives about half a year
in the pupa state, this condition lasts only about a month in the summer
generation. A higher temperature hastens the development.
Although the insect in the pupa state takes no food, it nevertheless
breathes, and therefore continually uses up body substance. This using
up only takes place to a small extent however, since the animal moves
but little. From whence, then, does the pupa get the material to cover
the loss of body substance? In the larval condition the insect takes far
more food than it requires for the development of its body, and from
this excess it builds up reserve stuffs, which are deposited in the
so-called “fat-bodies” of the larva. These reserve materials are
re-absorbed during the pupa state, and serve to maintain the breathing.
Consequently a pupa that has just been formed moves more than another
one just about to become a butterfly.
[Illustration:
FIG. 66.—Larva of a Weevil.
]
[Illustration:
FIG. 67.—A Hover Fly (_Syrphus pyrasti_). Fly, maggot, and pupa case.
]
The larvæ and pupæ of the different kinds of insects which undergo a
complete metamorphosis have not the same shape of body. Among the larvæ
may be distinguished _caterpillars_, _grubs_, and _maggots_. The
_caterpillars_ (Fig. 60) have a clearly marked head with hard covering,
three pairs of jointed thoracic legs, and a varying number of unjointed
pro-legs. They are usually variegated or green in colour, and are
divided into _true caterpillars_ and _false caterpillars_ (Figs. 60, 63,
and 64). The first, after the resting pupa stage, become butterflies or
moths; the latter saw-flies. The true caterpillars have two to five
pairs of pro-legs, the false caterpillars six to eight pairs. Reckoning
in the thoracic legs, therefore, the true caterpillars have altogether
five to eight, the false caterpillars nine to eleven pairs. The head of
the latter is more rounded, while that of the former is more flattened.
The way in which caterpillars walk depends upon the number of their
legs. If this is fairly large so that most of the segments of the body
are provided with legs, the whole body remains tolerably extended during
progression. But if the number is small—as in the looper caterpillars,
where there are three pairs of thoracic legs at the anterior end, and at
the posterior end only a terminal pair of legs (the caudal pro-legs) and
another pair in front of them—the middle legless region is strongly bent
during locomotion (Fig. 63). Hence the name “looper.” The loopers often
bend their bodies in a characteristic way. When at rest the hinder part
is coiled up spirally; but as soon as the animals are alarmed they throw
the hinder part of the body upwards and forwards and even over the head.
The _grubs_ (Figs. 66 and 69, _left_) have indeed, like the
caterpillars, a clearly visible hard head, but no characteristic
abdominal legs, or at most a pair of sucker feet at the end of the body
(wireworms). Thoracic legs are present in several grubs (cockchafer
larvæ, wireworms, leaf beetles); in others (larvæ of weevils and fleas)
they are entirely absent. _Maggots_ are those entirely footless insect
larvæ which do not possess a head clearly marked off from the rest of
the body, and the head-end of which is only to be recognized by the
presence of the mouth and mouth-parts. _Pupæ_ are enclosed in a case
which either only faintly indicates the outline of the various parts of
the adult insect, or else closely surrounds every part of the
body—wings, legs, antennæ, and even the mouth-parts and eyes. Pupæ of
the first kind are termed _obtectate_ (Fig. 60); those of the second,
_free_ (Figs. 61, 65).
Many pupæ are _naked_, others are surrounded by a web (cocoon) spun by
the larva (Fig. 60). There are also pupæ distinguished by the
peculiarity that when the insect has lived through the maggot-stage it
does not strip off its integument, but turns into a pupa inside the
shrivelled maggot-skin, from which the perfect insect later on breaks
out (Fig. 67).
The class of insects can be divided into eleven orders: (1) _Coleoptera_
(Beetles); (2) _Orthoptera_ (Grasshoppers, Locusts); (3) _Neuroptera_
(Dragon-flies); (4) _Hymenoptera_ (Bees, Ants, Saw-flies); (5)
_Lepidoptera_ (Butterflies and Moths); (6) _Hemiptera_ (Aphides, Bugs);
(7) _Physopoda_ (Thrips); (8) _Diptera_ (Flies with two wings); (9)
_Aphaniptera_ (Fleas); (10) _Pediculina_ (Lice); (11) _Collembola_
(Spring-tails and Tassel-tails).
ORDER I.: =Coleoptera= (BEETLES).
Beetles (Fig. 65) are insects with biting mouth-parts, and strongly
developed prothorax united with the mesothorax so as to permit free
movement. The fore wings are in the form of hard covers, leaving exposed
only the head, neck-shield (_i.e._ the dorsal side of the prothorax), a
three-cornered bit of the mesothorax (_scutellum_), and sometimes the
tip of the abdomen. Flight is effected by the hind wings alone, which in
a state of rest are drawn back under the wing-covers. The metamorphosis
is complete; the larvæ are legless, or with thoracic legs only, and have
a hard head with biting mouth-parts; change into free pupæ (p. 93).
Family: =Carabidæ= (_Ground Beetles_).
Usually elongated, slender; with long slender legs, five-jointed tarsi,
eleven-jointed antennæ, powerful jaws (Figs. 68, 69). Run rapidly;
usually keep on the ground; hide themselves during the day, but are very
active at night; with very few exceptions feed entirely on other
insects; when touched squirt an acrid stinking fluid out of the abdomen.
Larvæ longish, six-legged, with short antennæ and sharp jaws, with a few
exceptions live exclusively on other insects and lower animals.
Several species are of service, both in the adult and larval conditions,
since they destroy injurious insects, _e.g._ surface caterpillars,
wireworms, cockchafers, grubs, crane-fly larvæ. The following do good in
cultivated fields: =Golden Ground Beetle= (_Carabus auratus_), =Garden
Ground Beetle= (_C. hortensis_), =Granulated Ground Beetle= (_C.
granulatus_), =Cross-barred Ground Beetle= (_C. cancellatus_), =Field
Ground Beetle= (_C. nemoralis_), =Large-headed Ground Beetle=
(_Cephalotes vulgaris_), species of _Harpalus_, _Pterostichus_, etc.
[Illustration:
FIG. 68.—A Ground Beetle (_Carabus auronitens_).
]
[Illustration:
FIG. 69.—Corn Ground Beetle (_Zabrus gibbus_) and larva.
]
The only destructive form is the =Corn Ground Beetle= (_Zabrus gibbus_,
Fig. 69); short, thick-set; back black; belly, legs, and antennæ dark
brown. Larva cylindrical, slightly hairy, brown, with yellowish white
belly; head broad and flattened, black. The beetles (June, July) usually
remain hidden in the soil during the day, climbing up the stalks of
barley, wheat, and rye during the evening and in dull weather, and
eating the grain in the ear. The larvæ remain during the day in vertical
holes which they dig out; but at night and during dull weather they
devour the overground parts of the grain-plants mentioned above,
especially the hearts of young plants. They are destructive both in
autumn and spring, damaging winter and summer grain. The larval
condition is maintained for three years, the animal then turning into a
pupa during July. Its ravages are limited to special years. _Remedy_:
Sowing oats, peas, or vetches, or planting potatoes in fields infested
by the beetles or their larvæ; collecting the beetles in the evening
when they are in the ears.
Family: =Staphylinidæ= (_Rove Beetles_).
[Illustration:
FIG. 70.—Rove Beetle (_Staphylinus erythropterus_).
]
[Illustration:
FIG. 71.—The Black Burying Beetle (_Silpha atrata_) and larva.
]
Usually elongated, small (Fig. 70). The short truncated wing-covers
leave the whole of the abdomen exposed. The rove beetles resemble the
earwigs in their appearance and in a way they have of frequently lifting
up the hinder end of the body and turning it forwards. Tarsi
five-jointed, jaws strongly developed. The six-legged larvæ resemble
those of the ground beetles, but have a relatively large head. The
beetles live through the winter; the metamorphosis takes place in
autumn. Live on the ground under fallen leaves, also under the bark of
trees; in carcases. Some chiefly eat insects living in the soil and
noxious insects; others, dung and decomposing matter. (Species of
_Staphylinus_, and of _Ocypus_, e.g. _O. olens_, the =Devil’s Coach
Horse=.) Several are of service. A few devour the parts of plants.
_Anthobium torquatum_ is found in large numbers in the flowers of rape,
devouring the petals, stamens, and pollen.
Family: =Silphidæ= (_Burying_, or _Sexton Beetles_).
The antennæ either thicken gradually or have only the end-joints larger;
body flat; head projecting; tarsi five-jointed. The burying beetles and
their larvæ feed on dead animals. A few (sp. of _Necrophorus_) bury the
whole animal in the earth, and lay their eggs in it. Failing carrion,
some of them can live on vegetable food; these sometimes do harm. Others
prefer living insects and snails. They are of service in the economy of
nature by doing away with stinking bodies. The following are sometimes
harmful: =Black Burying Beetle= (_Silpha atrata_, Fig. 71), the larvæ of
which often do much damage in fields of beetroot; _Silpha opaca_ (=Beet
Carrion Beetle=), and _S. reticulata_, which, in the adult condition,
may do harm to several kinds of plants. Remedies need not be considered,
as it is only rarely they increase so largely as to make the supply of
carrion insufficient, and consequently attack plants.
Family: =Nitidulidæ= (_Shine Beetles_).
Small. Antennæ club-shaped, eleven-jointed. Tarsi five-jointed. A few
species live on carrion and on fungi, others under the bark of trees, a
few in flowers. To these last belongs the =Turnip Flower Beetle=
(_Meligethes æneus_); somewhat convex, elongated oval; shining metallic
greenish black, finely dotted. Occurs in the inflorescences of turnip,
rape, and allied species; also in the flowers of mustard, charlock, and
similar crucifers, and species of buttercup (_Ranunculus_). At the
beginning of spring, the turnip-flower beetle bores into the buds of
turnip, rape, etc., and, later on, attacks the flowers. It perforates
the petals, devours the stamens and pollen, and, lastly, the pistil. The
infested flowers wither. Three to four beetles are often found in a
single flower. The female soon lays her eggs, separately, in the ovary
of the flower. One to two weeks later the larvæ may be found in the
flowers, one or more in each. The larvæ, one-fiftieth of an inch long to
begin with, are, when ready to become pupæ, about one-fifth of an inch
long, cylindrical, yellowish white with blackish brown head; they have
three pairs of short thoracic legs, as well as a pair of caudal
pro-legs. Each segment of the body has two dark blotches on its upper
side. On an average, the larvæ reach their full size in four to five
weeks. They are first found at the bottom of the flower, where they gnaw
the stamens and ovary. They then wander from flower to flower, until
ready to become pupæ. If there are no more flowers in the neighbourhood
they attack the developing pods, first gnaw the green husk, then bore
through it and devour the young seeds. Become pupæ in the soil. The
beetle emerges after a fourteen days’ pupa rest. At least two, usually
three, sometimes four generations. _Remedy_: Rooting out charlock and
the species of buttercup. Selection of strongly growing varieties of
turnip, rape, etc., which blossom late (and therefore soon finish
blooming). Drill-culture.
Family: =Cryptophagidæ= (_Secret_-_eating Beetles_).
Very minute. Antennæ composed of eleven joints, of which the three last
form a club. Legs wide apart; tarsi five-jointed. Live in flowers,
fungi, dead parts of plants, under bark, in the earth, in humblebees’
and ants’ nests, etc. The =Beet Beetle= (_Atomaria linearis_) is
harmful: longish, egg-shaped, strongly convex; neck-shield as long as
broad. Brownish black or dark brown. In fields where beet is cultivated
for several years in succession, the beetles often increase in a
prodigious way. They attack the seedlings, and devour the base of the
stalk just below the surface of the soil, sometimes biting it half
through. The attacked seedlings often die even before the cotyledons
appear above the surface of the soil. Looking, therefore, in spring at
fields infested by the beet beetle, the seedlings will appear quite
normally developed in some few places, while in some other places there
may be no plants at all: in many spots, again, small plants will be seen
bearing only seed-leaves, withered and yellow. These cannot be pulled
out of the ground, for they break off at the place gnawed by the beetle.
It is often necessary to give two or three successive sowings, as the
young crop is attacked again and again. The larva of the beet beetle is
still unknown, though this undoubtedly develops in the beet-fields.
_Remedy_: Suitable rotation. When the conditions will not permit this,
the seed must be sown thickly, so that as many seedlings as possible may
remain sound, should the beetles exert their destructive influence in
the spring.
Family: =Lamellicornia= (_Chafers_).
[Illustration:
FIG. 72.—_a_, Antennæ of male; _b_, of female Cockchafer.
]
Body strong, stout (Fig. 65). The first joints of the antennæ have the
usual shape; the last, three to seven, are very short, but broadened out
on the inner side into leaf-like appendages, so that the end of the
antennæ is fan-shaped (Fig. 72). The little leaves are laid together
when at rest, so as to form a club-shaped thickened end; in flight, and
when the attention of the beetle is excited, they are spread out like a
fan. Legs strong; feet five-jointed. Flight rapid, somewhat awkward.
Larvæ thick; body cylindrical, but curved; head hard, brown; rest of the
body thin-skinned and yellowish white. The first three segments of the
body bear legs. The curved larvæ can move about in the soil, but not on
the surface. The beetles and larvæ devour vegetable substances; a
comparatively small number of species feed on dung.
[Illustration:
FIG. 73.—_a_, abdomen of Common; _b_, of Horse-chestnut Cockchafer.
]
The =Common Cockchafer= (_Melolontha vulgaris_) will serve as a type of
the lamellicorns (Fig. 65). The last segment of the body forms a
gradually tapering process. The club of the antennæ with seven large
leaflets in the male, and six smaller leaflets in the female (Fig. 72).
Head, neck-shield, entire ventral surface, and legs, black; although
these parts, with the exception of the head, may be reddish brown. Many
specimens are thickly clothed with numerous white hairs; others are
almost hairless. The beetles usually appear during May, but sometimes by
mid April, and sometimes not till the beginning of June. In the evening
they leave the soil and seek the neighbouring trees. They devour the
leaves and especially the buds of oak, horse-chestnut, beech, poplar,
willow, cherry, and other forest and fruit trees, but spare the lime and
generally the morel cherry. Of coniferous trees it only devours the
needles of larch and the young shoots of pine. Among cabbage-like plants
it only devours rape. In “chafer years” the cockchafer becomes a
veritable scourge to the farmer. For the purpose of laying her eggs
(about forty in number), the female selects by preference a fertile soil
rich in humus, but will also put up with a dry sandy soil. The grubs
devour the grass and clover-roots in meadows, and, in cultivated fields,
the roots of grain-plants, peas, and beans, rape, cabbage, etc., also
turnips and potatoes; in gardens the roots of many vegetables and
flowers, and, in particular, the underground parts of strawberry plants.
If, on poor sandy soil, they can get nothing else, they devour the bark
of oak and fir. Cockchafers take three to four years for their
development: four in England, North Germany, and Central Germany; three
in South France, Switzerland, the Rhine district, and Holland. In
regions where the insect is abundant, every third or fourth year is a
“chaferyear,” when the beetles appear in millions, while scarcely a
cockchafer can be found in the intervening years. In districts less
infested there is not the same marked distinction. It therefore appears
that cockchafers and their larvæ are to be reckoned as injurious
insects: their occurrence, however, is local. _Natural enemies_: moles,
shrews, bats, foxes, crow-like birds, starlings, sparrows, owls, and the
large species of ground-beetle. Winter floods do no harm to the grubs,
which are then deep in the ground,—but this is not the case with floods
occurring in summer, when they are near the surface eating the roots of
the plants. _Remedies_: Collecting the grubs turned up during ploughing.
Catching the cockchafers; this is very expensive, since it has to be
done very energetically if most of them have left the pupastage. A part
of the expense may, however, be recouped by using the cockchafers as
manure.
The =Horse-chestnut Cockchafer= (_Melolontha hippocastani_) has a short
slender caudal process, somewhat broader at the tip (Fig. 73). Its
habits are in no way different from those of the preceding species.
The =Buckwheat Beetle= (_Phyllopertha horticola_), one-third to
one-fifth of an inch long, without a caudal process. Shining blackish
green, with yellowish brown elytra. Dark-coloured specimens are also
found. The beetles appear in June; in some years they occur, like
cockchafers, in large numbers. Habits of the beetle and of the small
grub not markedly different from those of the cockchafer.
The =Rye Chafer= (_Anisoplia fruticola_), somewhat larger than the
buckwheat beetle, in other respects very like it, but with a snout-like
projection of the thickened skin of the head. Dark bronzy green, whitish
on the under side. Wing-covers yellowish brown. On poor sandy soil, on
the flowering ears of rye. The beetles gnaw the flowers.
[The =Garden Chafer= (_Anisoplia horticola_) is closely related to the
preceding. The grub is very harmful to pastures.]
Family: =Elateridæ= (_Click Beetles_).
[Illustration:
FIG. 74.—The Skipjack (_Agriotes lineatus_): 1, magnified larva, below
it the under side of the tip of the abdomen and the larva, natural
size; 2, the beetle; 3, under side of the head of the larva,
strongly magnified. _a_, maxilla; _b_, lower lip; _d_, labial palp;
_e_, _k_, inner and outer maxillary palps; _f_, antennæ.
]
The Click Beetles (Fig. 74) are longish, of equal breadth all along,
tolerably blunt at the hind end. Neck-shield strongly developed. Antennæ
“serrated,” _i.e._ made up of three-cornered joints. Feet five-jointed.
Looking at the under side a spine may be seen on the hinder margin of
the prothorax (Fig. 75, _b_), and on the mesothorax (_c_) a furrow which
receives the spine when the body is extended, but the spine is drawn out
of it if the prothorax and mesothorax are lifted up from anything they
happen to rest on (Fig. 75). A skipjack that has fallen upon its back
first draws its antennæ and legs close to its body, and then bends this
in such a way that the head and prothorax make an angle with the rest of
the thorax and the abdomen. In this way the junction of the prothorax
and mesothorax is lifted up, and the spine drawn as far as possible out
of the furrow. As soon as the beetle has taken up this attitude, it can
spring back into its usual position by lifting the two ends of the body
and pressing the spine forcibly back into the furrow, whereby it is
jerked against the ground with such a shock that its elasticity makes it
spring into the air, where it turns round and comes down again ventral
side below. The larvæ (“wireworms,” Fig. 74, 1) are like meal-worms,
elongated, always flattened on the ventral side, and sometimes on the
dorsal side as well. The head is dark brown, the twelve remaining
segments of the body yellow to yellowish brown; the first three segments
of the body bear three pairs of very small legs; the last segment has a
pair of caudal pro-legs.
[Illustration:
FIG. 75.—A Skipjack lying on its back and about to spring up. _a_,
head; _b_, spine of the prothorax; _c_, mesothorax; _d_, metathorax;
_e_, abdomen.
]
[Illustration:
FIG. 76.—Grain-plants sown deep and shallow; a wireworm is devouring
the underground part of the stem of the first.
]
Many species of click beetle are quite harmless, since they only devour
decaying vegetable matter, either in humus or in the rotting substance
of dying trees. There are also species, however, the larvæ of which feed
on the living roots of plants. The wireworms of _Lacon murinus_, which
are tolerably thick and have a flattened tip to the abdomen, devour the
roots of fruit trees, rose-bushes, various vegetables (lettuce, cabbage,
onions, turnips) and flowers; they are principally to be found in garden
soils rich in humus. The relatively small hairless wireworms which do
great damage, especially to grain-plants, but also to potatoes, carrots,
turnips, rape, hops, and almost all the plants of our arable land,
belong to _Agriotes lineatus_ or _A. obscurus_; the larger and more
hairy wireworms destructive in cultivated land almost all belong to
_Athous hæmorrhoidalis_ or a related species. The species named above
also do much damage in meadows and grass land. Those fields are most
infested which bore grass or clover the preceding year. Wireworms are
usually more destructive in dry soil than in wet. They devour all
underground parts, but specially prefer fleshy organs (potatoes,
turnips), as well as the underground stem-parts of grain-plants, working
themselves up from the soil into the inside of the lower part of the
haulm, where they destroy the plant by gnawing its base. They also often
destroy, in young grain-plants, the region of the stem which extends
from the remains of the seed to the surface (Fig. 76, _left_). In both
cases the plant is killed by the wireworms; the injuring of the roots is
less fatal. It is obvious that in shallow sowing only a small piece of
underground stem is exposed to the attacks of wireworms, in deep sowing
a much larger piece; besides this, a plant which has been sown shallow
develops earlier a strong mass of roots, and in its young state can
therefore offer a greater resistance to the destructive influence. Since
wireworms require four or five years for their development, the same
field is infested by them the whole year. The greatest damage is done in
spring and autumn. When wireworms have gnawed into the lower part of the
haulm, the lower leaves first turn yellow, and the death of the whole
plant soon follows. _Remedies_: Repeated ploughing of fields infested by
wireworms, so that rooks, starlings, wagtails, gulls, etc., can devour
them. Perhaps, too, many larvæ are frozen. Sowing the seed as shallow as
possible on infested fields (Fig. 76). Waste potatoes may be used as a
means of drawing them from the crop.
Family: =Curculionidæ= (_Weevils_).
Most species are small. Head lengthened into a proboscis (Fig. 79, 3);
the jaws are found at the front end of the proboscis, the eyes at its
base. The antennæ, which in most species are bent like a knee, and are
always thickened at the tip, are attached to the front end, middle, or
hinder end of the proboscis. The wing-covers usually extend to the tip
of the abdomen, and clasp it in several species. Feet four-jointed.
Weevils are mostly sluggish; many kinds do not fly at all; others only
during the breeding season. When disturbed they let themselves fall to
the ground as if dead. Almost without exception the females lay their
eggs within plants, boring a hole by means of their proboscis, and
shoving in the egg. The whitish larvæ (Fig. 66) are more or less curved
and limbless, with hard brownish heads.
[Illustration:
FIG. 77.—The Bean Beetle (_Bruchus rufimanus_) and beans gnawed by it.
]
The =Seed Beetles= (_Bruchus_) have a very short snout. Body short,
thick-set, almost four-cornered. The wing-covers leave the hinder part
of the body exposed. The female lays her eggs in the seeds of leguminous
plants. The larva hollows out one or several, becoming a pupa in the one
last inhabited. Here belong the =Pea Beetle= (_B. pisi_), the two =Bean
Beetles= (_B. rufimanus_ and _B. granarius_), of which the last-named
also lives in vetches and chickling peas, and the =Lentil Beetle= (_B.
lentis_). The =Pea Beetle= (_B. pisi_) is black, with brown hairy
covering flecked with white. Like all other species of seed beetle, it
becomes a pupa in the last seed inhabited by the larva, and the pupa
changes into a beetle in autumn. A pea inhabited by such an insect can
be recognized by a black translucent patch, since the beetle has become
a pupa immediately under the seed-coat. Late the following spring the
beetle crawls out. As the beetles are usually still in the peas at the
time of sowing, the process brings them into the fields. Later on, when
the beetles crawl out, they lay their eggs in the ovaries of the flowers
of the pea-plants, which have meanwhile developed. The _remedies_ are,
consequently,—late sowing of the peas, or killing the beetles in them by
exposure (for two minutes) to a temperature of 122° Fahr., or for ten
minutes to sulphur dioxide fumes in a closed space. The remaining three
species of Bruchus have the same habits as the bean beetle, but the
insect often creeps out much earlier, so that the seeds do not require
treatment.
[Illustration:
FIG. 78.—Attacks of Pea Weevil: _a_, _b_, on pea leaves; _c_, on a
bean leaflet.
]
The =Pea Weevil= (_Sitones lineatus_). Longish, with grey scales on a
black background. Neck-shield with three longitudinal streaks,
wing-covers with dotted lines. These weevils appear at the first
beginning of spring on peas, field and garden beans, clover, and
vetches. They gnaw the leaf-margins of the tender plants, and always in
such a way as to present a toothed appearance (Fig. 78). It often
happens that in a large field one can scarcely find a pea-leaf with
uninjured margin. When the plants are somewhat grown the damage done by
the weevils is of no further importance; but if the plants, when still
very young, are prevented from growing rapidly by reason of rough cold
weather or unfavourable conditions of soil, while at the same time the
weevils continue their attacks, the small leaves will be completely
destroyed, and the plants will perish. The larvæ gnaw the roots of the
plants infested by the weevils. _Remedy_: rational rotation.
The =Mouse-tooth Weevils= (_Baris_, or _Baridius_). Small, tolerably
elongated weevils with fairly long neck-shield (Fig. 79). Develop in
cruciferous plants. The =Rape Mouse-tooth Weevil= (_B. chloris_).
Shining green. Leaves in spring its hiding-place in the soil; the female
then lays her eggs in the leaf-axils or stem of rape or turnip. The
larva eats out passages in the stem and branches; in July it becomes a
pupa in the inside of the stem; in late summer the beetle appears, and
quickly creeps into the soil. _Remedy_: Pulling up and burning the rape
and turnip stubble, which harbours the weevil. The =Pitchy Mouse-tooth
Weevil= (_B. picina_), one-sixth of an inch long, shining black. Similar
habits to the previous species; but lives exclusively in headed cabbage
and cauliflower, never in rape and turnip. The =Cress Mouse-tooth
Weevil= (_B. lepidii_), black with blue or greenish-blue back,
one-eighth of an inch long. Lives in the stems of cauliflower and garden
cress.
[Illustration:
FIG. 79.—Mouse-tooth Weevil (_Baridius chloris_). 1, _larva_; drawn on
the left, natural size,—above, the magnified head: 2, _pupa_,
magnified: 3, _beetle_; drawn of the natural size above: _a._, eye;
_g_, antennary groove with antenna not drawn back.
]
[Illustration:
FIG. 80.—Turnip Gall Weevil (_Ceutorhynchus sulcicollis_).
]
The =Gall Weevils= (_Ceutorhynchus_) are very small beetles with
thick-set bodies. In a state of rest the proboscis is folded back into a
ventral furrow, situated between the fore-hips. They are black, and
thickly covered with grey hairs. Live on cruciferous plants. The =Turnip
Gall Weevil= (_Ceutorhynchus sulcicollis_), one-eighth of an inch long,
dull black, with many grey hairs on the ventral side and few on the
dorsal side. The deeply pitted neck-shield has in its centre a
well-marked longitudinal furrow. Wing-covers deeply furrowed. The beetle
appears in April, and gnaws the flowers and shoots, but can scarcely be
considered as harmful. In late summer or autumn, after the sprouting of
the winter rape, the female bites into the root immediately under the
surface of the soil, or into the lower parts of the stem, so as to form
a hole in which she lays one or two eggs. As the larva begins to
develop, the surrounding parts of the stem or root grow into a gall-like
swelling (Fig. 80). At the beginning of spring the developed larvæ creep
out, and become pupæ in the soil; in April the beetle appears. If the
Ceutorhynchus galls are only present in small numbers they damage the
rape plants only to a small extent, but when ten to twelve are found in
one plant the roots grow crooked, and remain short, and consequently the
growth of the overground parts is detrimentally affected. Ceutorhynchus
galls are found, not only on rape, but also on the different kinds of
cabbage, and on turnip plants. In the last case they often occur in such
numbers that the turnips do not develop at all, and the overground parts
also remain small. There is a similar form (_C. assimilis_), as large as
the preceding species, but somewhat slimmer, and, on account of greater
hairiness, greyer. Appears in spring on flowering rape and several kinds
of cabbage, as well as on similar cruciferous plants. It is harmful
because the beetles gnaw the buds and flowers, and the larvæ feed on the
seeds within the pods. The attacked pods ripen early, and open so that
the larvæ fall to the ground, where they become pupæ. Usually only a
single larva is found in each pod. The =Rape Gall Weevil= (_C. napi_),
somewhat larger than the two preceding species, has a neck-shield which
projects strongly forward like a collar, and is marked by a median
longitudinal furrow. It is covered with yellowish-grey hairs. At the
time when rape blooms it appears upon the flowers. The female lays her
eggs singly in a hole previously bored in the stalk by her proboscis;
during spring and early summer the larva eats out the stem, which turns
brown inside, and becomes diseased or even dies.
Family: =Chrysomelidæ= (_Leaf Beetles_).
[Illustration:
FIG. 81.—Potato Beetle (_Chrysomela decemlineata_).
]
Small, generally thick-set beetles, arched on the upper side, with
eleven-jointed antennæ thickening somewhat towards their tips, and
four-jointed feet. The first joints of the feet are covered with
felt-like hairs on their under sides (Fig. 81). The larvæ have three
pairs of thoracic feet, and, in addition to this, there are in most
species a pair of caudal pro-legs. Live in the inside parts of plants
(stems, leaves), and are usually elongated and yellowish white; those
which live on the outside of plants are more convex, shorter, and
thicker, more or less hairy, often of a striking colour, and always with
dark spots. The beetles eat leaves; the larvæ feed upon parts of the
same plants, sometimes living outside upon the leaves, or it may be
excavating channels in the inside of a leaf or of the stem. Most leaf
beetles lay many eggs, and in many species there are several generations
annually. The plants attacked by them are often stripped quite bare.
Here belongs the blue =Alder Leaf Beetle= (_Galeruca alni_), the =Poplar
Beetles= (_Chrysomeli populi_ and _C. tremulæ_), the =Asparagus Beetles=
(_Crioceris merdigera_ and _C. duodecimpunctata_), etc. Of species
injurious agriculturally, I will first mention the =Colorado= or =Potato
Beetle= (_Chrysomela decemlineata_). This beetle originally lived in the
west of the United States on wild solanaceous plants; but as soon as
potato culture extended to the west the beetles also attacked potato
plants. As soon as the insects had spread to this plant they began to
appear in great numbers owing to their very great powers of
reproduction; and they quickly spread from one field to another, always
going further and further east. 1859 was the first year when they became
notorious as pests, and, since they first appeared as such in the State
of Colorado, the insect received the name “Colorado Beetle.” In a short
time the beetles spread to the east, especially to places where potato
culture was carried on; in 1865 they crossed the Mississippi, and in
1870 they were already spread over the states of Indiana, Ohio,
Pennsylvania, Massachusetts, and New York. They were soon found in all
the eastern states, and European farmers began to be alarmed. In most of
the countries of Europe police regulations were made for the purpose of
preventing the introduction of the unbidden guests. Colorado beetles
have indeed been brought several times to Germany on board ship, but in
almost all cases the pests so introduced have been recognized and
caught. Twice during 1877 they were able to increase (Mulheim,
Schildau), and the same thing has happened once at a more recent date
(Torgau); but the vigorous action of the authorities quickly
exterminated the beetles.
[Illustration:
FIG. 82.—Colorado Beetles: _a_, eggs; _b_, _c_, _d_, younger and older
larvæ; _e_, pupæ seen from the ventral side and from the dorsal
side.
]
Beetle (Fig. 81), half an inch long, dusky yellow, with five
longitudinal black streaks on each wing-cover, and black markings on the
neck-shield. Larva (Fig. 82), half an inch long, thick, fleshy; legs
short and weak. Orange-yellow, with shining black head, and with black
spots on the body segments. The younger larvæ are darker, almost blood
red. When the young potato plants come up, the beetles which have
survived the winter creep out of the soil and devour the margins of the
young leaves. The female lays her yellow eggs (700 to 1200?) in heaps on
the leaves (Fig. 82, _a_). After a week the larvæ appear, and carry on
the work of the beetles. They attain their full development in seventeen
to twenty days, become pupæ in the soil, and the beetles of the second
generation make their appearance in the middle of June. Still a third
generation may appear the same year. Since a considerable time elapses
between the laying of the first and second batches of eggs, one usually
sees eggs, larvæ, pupæ, and beetles at the same time. Entire potato
fields are eaten bare by the beetles and their larvæ, the formation of
the potatoes being quite prevented. _Remedies_: Energetic measures must
be taken on the first appearance of the beetle in any district. Where
possible, all the beetles and larvæ must be collected, the plants being
dug up and destroyed with the beetles, pupæ, larvæ, and eggs adhering to
them. Petroleum must then be poured over the whole field and set on
fire, so as to destroy any insects which may be hidden in the soil.
Spraying the attacked plants with Schweinfurt green.
[Illustration:
FIG. 83.—The Cloudy Tortoise Beetle (_Cassida nebulosa_).
]
The =Cloudy Tortoise Beetle= (_Cassida nebulosa_)—Fig. 83. One-fifth to
one-fourth of an inch long; the broad neck-shield projects in front over
the small head. The wing-covers, too, are much broader than the body of
the animal; they are longitudinally ribbed. Dorsal side reddish brown,
in young individuals greenish; always with black spots. Ventral side
black. Larva elongated oval, yellowish green. Segments of the body beset
with thorn-like structures bearing lateral branches; the last segment
possesses a “tail-fork,” which the larva usually carries bent over its
back and on which it heaps up its dung. The beetles which have survived
the winter usually attack in spring only wild goose-foot and orach
plants, on which they lay their eggs in heaps. The larvæ quickly appear,
and to begin with chiefly keep to the under sides of the leaves. They
are sluggish, grow quickly, and devour the leaf substance; when fully
developed they cement themselves to a leaf and become pupæ. In June the
beetles of the second generation appear, which again lay their eggs on
the leaves. In favourable weather there may be even a third generation.
In many it happens that the beetles of the second generation migrate to
beet or mangold plants, sometimes damaging them to a very great extent.
_Remedy_: Rooting out species of goose-foot or orach.
The =Earth Fleas=, or =Flea Beetles=, are all small leaf beetles with
the power of springing, and therefore provided with thick thighs. Here
belong:—
[Illustration:
FIG. 84.—The Rape Flea Beetle (2) with hind-leg of the same; larva (1)
and its head.
]
The =Rape Flea Beetle= (_Psylliodes chrysocephalus_)—Fig. 84.
Egg-shaped. Hind feet not inserted at the ends of the shanks, but higher
up. The first joint of the foot is as long as the others put together.
The rest of the hind foot is bent in a knee-like way on the first long
joint. Shining blackish brown or blackish green, rarely brownish. Larva
one-fifth to one-fourth of an inch, dusky white; head, neck-shield, and
last segment of the body blackish brown. In spring and during the entire
summer the beetles are found upon the plants of winter rape. Although
they gnaw the leaves and the immature shoot the damage caused is small.
In late summer or autumn the female beetles lay their eggs separately at
the bases of the leaf-stalks of the young winter rape plants. The larvæ
which emerge bore into the leaf-stalk, and eat it completely out during
autumn, winter, and spring, so that the leaf dies. Since the eggs are
laid separately the larvæ do not all develop at the same time in the
spring. In spring many larvæ eat their way from the leaf-stalks into the
still very short stem, which consequently ceases to develop. It often
happens that most, or even all, of the plants in a rape field are
withered; on poor soil the whole crop must be at once ploughed up; but
on fertile soil the plants often develop much better than one would
believe. Plants whose stem has been killed in the winter while still
short may develop a few (3 to 5) branches from buds situated near its
base, but these usually remain small, and do not yield a large crop. The
beetles, appearing in spring, lay their eggs on the lower leaf-stalks of
the rape, either on the old plants of winter rape or young plants of
summer rape. In the latter case the summer rape is quite spoilt in the
same way as the winter rape during the previous winter. In the former
case the larvæ eat out the lower part of the leaf-stalks, and make their
way into the stem, hollowing it out at a definite spot in such a way
that it is no longer able to hold itself up, especially when the shoots
and seeds develop. The stems bend and become kneed, sometimes to such an
extent that the rape field looks as if persons or cattle had been
running about in it in all directions, and treading everything down.
Meanwhile the larvæ bore their way out of the stem, and become pupæ in
the soil. In late summer the beetles appear, and once more lay their
eggs on the leaf-stalks of the winter rape. There are, therefore, two
generations annually. _Remedies_: Never sow summer rape after winter
rape which has been destroyed by the beetle and ploughed up. Temporary
limitation of rape culture.
The =Cabbage Flea Beetle= (_Haltica oleracea_), one-fifth to one-sixth
of an inch long, longish oval, dark green, metallic sheen. The hind legs
do not possess the peculiar features of the rape flea beetle (p. 114).
Larva one-fifth to one-fourth of an inch long, greyish black, with
bristly hairs, and with two rows of shining black warts. The beetles
attack, in the spring, chiefly cabbage, rape, radishes, horseradish; but
do not spare other plants (_e.g._ peas and beets) as well. Seedlings are
chiefly attacked, and in all cases only young plants are devoured. Since
both seed-leaves and terminal buds are eaten, much damage is done,
especially during continuously dry weather. It must often happen that
the beetles wander away, to find other species of plants for the purpose
of egg-laying; so that it is exceptional to find the larvæ upon species
of cabbage. These larvæ are much less injurious than the beetles, since
they usually only prey upon mature plants. In their youngest condition
they are found in groups, feeding upon the leaves; this results from the
eggs being laid in little heaps. Later on, they wander away from one
another. In favourable weather they are fully grown in six weeks, and
several generations may succeed one another in the same year.
_Remedies_: Destruction of the weeds which attract the beetles
(charlock, shepherd’s purse, yellow rocket, treacle mustard, etc.) Good
preparation of the soil, suitable manuring and drill culture, since
these bring about a more rapid growth of the plants. Thick sowing (but
not too thick), so that, even after the destruction of many seedlings, a
sufficient number may remain. Moistening the fields by means of
water-carts or sprayers. In garden-beds twigs are laid down, by which
the seeds are protected against birds and the seedlings against flea
beetles. “Flea-beetle machines,” consisting of a board smeared with tar,
which is drawn across the field, so that the frightened beetles spring
up, and remain hanging in the sticky substance. After rain, or when dew
is still clinging to the plants, they should be strewed with powdered
fowls’ dung, pigeons’ dung, or horse dung, wood-ashes, road-dust,
powdered lime, coal-ashes; or the plan of sprinkling with a decoction of
wormwood may be adopted.
The =Turnip Flea Beetle=, or =Turnip Fly= (_Haltica nemorum_), one-tenth
to one-eighth of an inch long, egg-shaped, black, with longitudinal
streaks of a sulphur yellow colour on the thickly pitted wing-covers.
Larva one-fifth of an inch long, yellowish white, with dark brown head,
neck-shield, and last body segment. The adult beetles have the same
habits as in the preceding species; they also do damage in the same way,
and attack the same plants, especially in the seedling condition. The
female, however, does not lay her eggs in heaps, but separately on the
leaves, and always on the under side. The larva bores into the leaf, and
digs a passage, which, like the animal inhabiting it, is at first small,
but gets gradually larger. In fine weather the larva is fully developed
in a week. It then pierces the skin covering the under side of the leaf,
falls to the ground, and becomes a pupa. Several generations may appear
every year, if the weather is favourable (dry). This species is quite as
harmful as the preceding, chiefly in the mature condition. _Remedies_:
Compare the preceding species.
Family: =Coccinellidæ= (_Lady-birds_).
Hemispherical; upper side convex; under side flattened. Head small,
retractile. Antennæ, eleven-jointed, thickened at their tips. Legs
short; feet apparently three-jointed—in reality four-jointed, the second
joint, however, being very small. Colour, usually variegated; many
species black with red, or red with black spots. When grasped, they let
a yellowish, unpleasant-smelling fluid escape from the abdomen. The
blunt, four-cornered, usually variegated pupæ hang on the leaves. The
fully developed larvæ are longer than the beetles. They closely resemble
those of the leaf beetles, but are not so thick-set, and their longer
legs stick out more laterally. They are covered with warts and little
spines (Fig. 85). The larvæ and beetles of most species feed chiefly on
aphides and shield-lice; they are therefore of use, and this is
especially true of the exceedingly ravenous larvæ. The larvæ of the
Seven-spotted and Two-spotted Lady-birds, in particular (_Coccinella
septempunctata_ and _C. bipunctata_), are found in large numbers among
aphis colonies. The yellow eggs are laid in heaps.
[Illustration:
FIG. 85.—The Seven-spotted Lady-bird (_Coccinella septempunctata_):
larvæ, pupæ, beetles; all natural size.
]
SECOND ORDER: =Orthoptera= (STRAIGHT-WINGED INSECTS).
Insects with biting mouth-parts and incomplete metamorphosis (p. 89).
Four wings, of which the anterior are usually harder than the posterior;
hind wings membranous, broader than the fore wings, and folded like a
fan. The Orthoptera feed entirely, or almost so, upon vegetable
substances. To this order belong:—the =Earwigs= (_Forficulariæ_), which
feed on sweet fruits and flowers, and are sometimes very injurious; the
=Cockroaches= (_Blattariæ_), which do much damage to provisions in
kitchens, stores, and on board ship; the =Grasshoppers= (_Acrydites_),
to which, besides the =Migratory Grasshopper= (_Acrydium migratorium_)
Fig. 62, various species of meadow grasshoppers belong, which are quite
harmless; the =Locusts= (_Locustidæ_), to which the well-known =Green
Locust= (_Locusta viridissima_) belongs; and the =Crickets=
(_Gryllidæ_), to which belong, among others, the =House Cricket=
(_Gryllus domesticus_), the quite harmless =Field Cricket= (_Gryllus
campestris_), and the =Mole Cricket= (_Gryllotalpa vulgaris_).
The =Migratory Grasshopper= (_Acrydium migratorium_).
1⅗ to 2⅗ inches long; spread of the wing, on the average, 2½ inches.
Greenish grey. Under side flesh colour. Wing-covers brownish, darkly
flecked. Colour very variable (Fig. 62). Excessive multiplication and
migrations of this insect often take place in South Russia and Turkey;
but they may also appear in Central Europe. In North Germany, for
example, the following years of this century were “grasshopper years:”
1803, 1825–27, 1853, 1875–76. In many cases the appearance of swarms of
grasshoppers in Central Europe is due to migration from Russia and
Hungary; but it also often happens that the insects which appear in such
large numbers have been bred in the places where they are found. Since
the female lays, on the average, 150 eggs, excessive increase may take
place in any country to which they are indigenous—and therefore in
Central Europe. It appears, however, that a large number of grasshoppers
are usually killed by their natural enemies, such as cold and damp
weather. Excessive increase may, however, take place in exceptionally
favourable years; and since the larvæ, which are incapable of flight,
devour everything available, the mature insects developed from them are
forced to migrate. Where they descend they destroy everything they find
in the fields. _Remedies_: Destruction of the longish eggs, which are
laid in heaps in the earth of fallow ground and meadows. In all those
places where dead insects are found in large numbers on the ground many
eggs will also be discovered, for the insects keep on laying till they
sink down dead in the place where the last heap of eggs was deposited.
Such places should be dug or ploughed, and the eggs, which are present
in thousands, either collected or else searched out by pigs, ducks,
geese, and fowls, which have been driven to the spot. Destruction of the
young animals while still incapable of flight. Working the soil with
harrows, rollers, and cultivators will be effective here. The adult
grasshoppers must for the most part be destroyed with fire. [Heaps of
straw and brushwood are soaked with paraffin and then set on fire.]
The =Mole Cricket= (_Gryllotalpa vulgaris_).
Body stout and flattened. Antennæ, palps, and tail-filaments very long.
Fore legs broad, modified into true “digging legs,” superficially
resembling the feet of a mole. Fore wings broad, but short, leathery. In
a state of rest, the hind wings lie on the back, like a couple of tails.
Colour dark brown. Principally occurs on peaty soils mixed with sand or
clay, also on all soils which have become of firm consistency by the
application of much manure. Their presence is therefore local. Very
early in the year the mole-cricket leaves its winter hiding-place, and
begins to make its passages near the surface. Where the female makes her
nest the passage turns downward a little. The nest is 1⅗ of an inch in
diameter, and its walls are compacted by the pressure of the hard body.
The number of eggs is from 200 to 250; they are laid in lots with a few
intermediate spaces. The young creep out in the spring, and are
wingless. To begin with, they are white, but quickly become brown. The
mother guards her young very carefully. These grow tolerably fast, and
first begin to lead an independent life after the second moult. In
October and November they undergo a third moult. Then, still in a
wingless condition, they hide themselves, and do not moult again till
April or May, when the wing-cases appear; while after the fifth moult
(May, June) the mole-cricket becomes an adult insect, capable of
reproducing. This insect is found in cornfields, gardens, grassland, and
meadows, also in orchards and woods. It gnaws the roots of all kinds of
plants, and often effects great damage in this way. The mole-cricket is
also harmful on account of its passages, which are dug close to the
surface. In this way it lifts young plants out of the soil; while older
plants are killed, both by its gnawing and by its digging. Such plants
can often be pulled up by grasping the leaves. All the plants wither in
the place where the nest is found. Dry, cold winters kill almost all the
mole-crickets; much drought in summer and also continuous wet are
unfavourable to them. _Enemies_: moles, rooks, etc., butcher-birds,
starlings, and the larger ground beetles. _Remedies_: Destruction of the
nests, in June, to begin with, but also to be continued later. In those
parts of a field where the plants are yellow or withered in a large
circular patch (some 39 inches in diameter) the nest is felt for with
the finger, and carefully lifted up, so that the eggs do not fall out.
Mole-crickets can also be caught by means of flower-pots. The apertures
in the bottoms of these are stopped with corks, and they are then sunk
in the soil with their mouths on a level with the mole-cricket passages;
they thus serve as pitfalls, from which the insects cannot escape. If
during winter little heaps of horse dung are placed on the ground, the
insects creep into them for the sake of the warmth, and can thus be
collected and killed.
THIRD ORDER: =Neuroptera= (NET-WINGED INSECTS).
Insects with biting mouth-parts and four similar membranous wings, with
numerous veins arranged in a net-like manner. The metamorphosis is
either incomplete (p. 89: dragon flies, may flies, book lice), or
complete (p. 89: ant lions, lace flies, snake flies, scorpion flies,
caddis flies). The indigenous forms, with the single exception of book
lice, feed upon animal food, usually on the juices of other insects.
Several of them are tolerably useful in this way.
The =Dragon Flies= (_Libellulidæ_) fly about incessantly from place to
place on bright warm days, and catch a large number of insects,
especially butterflies and flies, among which are many that are harmful.
The larvæ live in water, and feed on insects and such small deer, which,
however, are of no importance to forestry or agriculture. They also
devour fish-spawn, and may therefore be injurious in that way.
[Illustration:
FIG. 86.—The Common Lace Fly (_Chrysopa vulgaris_): _a_, eggs; _b_,
the larva; _c_, cocoon; _d_, pupa contained in the same; _e_, open
cocoon; _f_, adult insect; _a_, _c_, _e_, natural size; _d_,
enlarged and natural size; _b_ and _f_ enlarged.
]
The =Lace Flies= (_Hemerobidæ_) when at rest are covered as with a roof
by their fore and hind wings, which are almost alike, clear as glass,
and finely veined. Head tolerably large, eyes large, abdomen elongated
and slender. The extremely rapacious larvæ (Fig. 86, _b_) feed on the
juices of the bodies of other insects, which they suck up by means of a
pincer-like organ situated on either side of the mouth. The two pincers
are perforated, and the tubes open on each side into the gullet; the
body juices of the insects attacked thus flow into the gut of the larva.
This is strongly built, and always much thicker and larger than the
adult insect. Metamorphosis complete. Three genera belong to the lace
flies:—
1. The delicate greenish, or greenish yellow, illsmelling =Gold-eyed
Lace Flies= (_Chrysopa_), the larvæ of which chiefly feed on plant lice
(a few species on caterpillars, also, and other small insect larvæ).
2. The =Aphis Lions= (_Hemerobius_: _H. hirtus_, with hairy veins on the
fore wings; _H. dipterus_, with hind wings almost entirely absent), the
larvæ of which also feed on aphides, and make a case from their
sucked-out skins.
3. The =Ant Lions= (_Myrmeleon_), of which the fat, thick-set larvæ,
which have a large head and strong grasping pincers, dig out in the sand
funnel-shaped holes, at the bottom of which they hide, lying in wait for
ants and the like, which step on the edge, when the sand gives way and
causes them to fall in. The species of the first two genera are of
service as destroyers of aphides; the ant lions are of no importance.
The =Scorpion Flies= (_Panorpatæ_) have attached to the head a kind of
proboscis, the upper side of which is formed by a prolongation of the
forehead, and the under side by the maxillæ and lower lip, while the
upper lip and mandibles are hinged on at its tip. Here belongs the
slender-bodied =Scorpion Fly= (_Panorpa communis_), an insect found in
May, and again in July or August, on the leaves of trees and shrubs,
when it is sunny. While the abdomen of the female ends in an ovipositor,
it bends upwards in the male, and terminates in a pincer-like organ;
hence the name “scorpion fly.” Wings flecked with brown. Scorpion flies
catch on the wing a very large number of butterflies and moths, and are
therefore useful to some extent.
FOURTH ORDER: =Hymenoptera= (MEMBRANOUS-WINGED INSECTS).
Upper lip and mandibles short; the latter used for biting. Maxillæ
loose-jointed, so that they can be stretched out considerably; elongated
in those which lick the juices of flowers. In the last-named forms the
larva’s lips are still more elongated, and may even form a tongue or
proboscis-like organ, which may bear lateral appendages (“secondary
tongues”). Wings, four, all membranous, with relatively few veins (Figs.
61, 90). Metamorphosis complete; larvæ very various; pupæ free (p. 93).
The female usually possesses an ovipositor, the structure of which
varies a great deal, and which serves in many species, not only for
egg-laying, but also for protection (digging wasps); in others
exclusively for offence or defence (“stings” of bees and wasps), while
the same opening serves for the passage both of eggs and excrement. The
abdominal glands, secreting a sticky substance by which the eggs are
attached, are modified into poison-glands in those Hymenoptera which
possess a sting. In those forms where the ovipositor is not modified
into a sting, it is used for piercing, biting, or sawing. The
Hymenoptera with saw-like ovipositor first make an opening in wood or in
a leaf by means of the saw-teeth in its edge, and then lay an egg in
this hole.
[Illustration:
FIG. 87.—Head of Honey Bee. _A_, compound eyes; _a_, simple eyes; Fh,
antennæ; _Z_, tongue (under lip); _b_, labial palps; _Fz_, elongated
maxillæ; the mandibles and upper lip remain short.
]
Many Hymenoptera (all digging wasps, gold wasps, ichneumon flies, and
gall flies—several true bees and wasps) live alone, or in pairs. Others
form colonies, in which division of labour is always so far carried out
that there are _reproductive individuals_ and _workers_. The former
(males and females; in colonies of bees—“drones” and “queen”) are only
present in small numbers in any particular colony. They live merely for
the perpetuation of the species. At most the males seek their own food,
while the females are usually fed by the workers. Workers, on the other
hand, are individuals in which the (female) reproductive organs remain
in a low state of development, so that they are sterile. They seek food
for the larvæ, and usually for the adult reproductive individuals as
well. They also wage war against strange intruders.
Family: =Apidæ= (_Bees_).
The bees, by means of their very much elongated mouth-parts (maxillæ and
lower lip or “tongue”), collect honey from many different kinds of
flowers. Body somewhat unwieldy, usually hairy. The fore wings are not,
as in wasps, folded together longitudinally when in a state of rest.
Eyes round. The legless, almost maggot-like larvæ are fed with pollen or
with a mixture of pollen and honey.
Most bees are colonial, and in these we find, besides the reproductive
individuals, workers which prepare the nest. This is for the most part
made up of “cells,” in the construction of which the most various
substances are used according to the species, _e.g._ wax, sand grains,
chewed wood, fragments of leaf. In each nest there is at the same time
only _one_ queen, who lays her eggs in the cells; the larvæ are
therefore developed in these cells, other cells serve for the storage of
pollen or honey. In the non-colonial bees there are no workers; in a few
of these species (parasitic bees, cuckoo bees) the female lays her eggs
in the cells of other species, which, like foster parents, undertake the
care of the strange larvæ. These species are naturally devoid of the
apparatus for securing and carrying pollen. In several bees (honey bees,
humblebees) this end is attained by the much-broadened shanks and first,
very large foot-joints of the hind legs. Other bees (_Megachile_) carry
pollen on the under side of the abdomen.
Bees play a very important part in the pollination (fertilization) of
many cultivated plants.
The =Honey Bee= (_Apis mellifica_) cannot be spoken of here; reference
must be made to works on apiculture.
The =Humblebees= (_Bombus_) are tolerably large, stout, thick-set, and
hairy. They construct nests below the surface of the soil (often in
peaty places), made up of oval or irregular waxen cells the size of a
hazel-nut. They fly rapidly, always making a humming sound. Many species
are black, with yellow and white, or red transverse stripes.
Honey-producing flowers in which the corolla is so long that even the
proboscis of humblebees cannot reach the honey hidden at the bottom of
the flower, (tobacco, field and garden beans) are gnawed at their base
by the sharp mandibles of the bees, so that a hole is made in the calyx
and corolla through which the tongue can be put. In this way the ovary
is sometimes wounded, and the normal development of the fruit rendered
impossible. Perhaps a certain amount of damage, always however
inconsiderable, may thus be effected.
Family: =Vespidæ= (_Wasps_).
Mouth-parts as in bees. Also with stings. Slender, and either hairless
or only slightly hairy. Eyes kidney shaped. Fore wings folded together
longitudinally when at rest (Figs. 61 and 88).
A distinction is made between solitary and social wasps; the latter
possess males, females, and workers. Only the fertilized queens survive
the winter. In the spring each of these begins to construct a nest (Fig.
88). In the wasp’s nest each comb consists only of a single layer of
cells, the openings of which are turned downwards. In a single nest
several of these horizontally placed combs are usually found one over
another, and are connected together by means of vertical pillars. Some
nests are built in hollow trees, others in holes in the ground; others
hang freely from trees, in which case they are covered by several layers
of a papery substance. The combs and cells are also made of paper, to
prepare which the insect gnaws and crushes decaying wood, and especially
bark, with its mandibles, mixing the crushed material with saliva. In
this way a pulp is made which is used in the construction of the nest,
and dries into a kind of paper. The opening of the nest is in its under
side (Fig. 88).
[Illustration:
FIG. 88.—The Common Wasp (_Vespa vulgaris_) and its nest.
]
During spring and summer the queen, or “wasp-mother,” lays only eggs
from which workers are hatched, which undertake the work of
nest-construction and care of larvæ, so that the queen can devote
herself exclusively to the function of reproduction. Towards autumn
males, and females capable of being fertilized, are also hatched; these
last afterwards live over the winter in the fertilized condition.
During summer the larvæ are fed by the workers with finely chewed
insects or with honey. They do not, however, suck the honey from
flowers, but steal it from several species of bee, or else form it in
their stomachs from sugary materials drawn from sweet fruits.
Wasps are harmful or troublesome in three ways: (1) by gnawing the bark
of trees; (2) by feeding on sweet fruits; (3) by the painful stings
which they inflict. These are most dangerous in hot summer days. If a
nest situated in the soil is destroyed during ploughing the alarmed
insects attack both men and horses, cases being known where their stings
have proved fatal. The pain is chiefly caused by the poison introduced
into the wound. On this account if the sting remains sticking in the
skin it must not be drawn out simply with the fingers, but carefully, by
means of the nails, lest the poison-bag is pressed and thus still more
poison brought into the wound. _Remedies_: Cooling substances, _e.g._
ground carrots, apples or pears, cabbage leaves, damp sand. Rubbing in
ammonia. If there is acute inflammation, a compress with sugar of lead.
Family: =Fossores= (_Digging Wasps_).
Several species of this group resemble the wasps in their habits, as
well as through their black and yellow-tinged abdomens; but they are
always distinguished from these by their fore wings, which are not
folded together in a state of rest, and by their eyes, which are not
kidney shaped. The shanks and feet possess thorns serviceable for
digging. The sting of the female has no barbs, so that it is not torn
off and left behind in the wound. The digging wasps are not social. They
are lively and active; in summer the female often flies busily about
near the ground in order to find a place for bringing up her young. She
digs a hole in the earth in which she lays an egg. Then she buries an
insect to serve as food for the young when hatched. Lest the insect to
be buried should decompose, while, on the other hand, a living animal
would not allow itself to be buried, the wasp first brings the insect
into a condition in which it cannot make any voluntary movements. For
this purpose most species sting the captured prey several times in the
body, and thus often injure the ventral ganglia (p. 84); by this
treatment the insect is not killed, but reduced to a condition of
apparent death. Most digging wasps are useful, since they chiefly bury
destructive kinds of insects. The =Common Sand Wasp= (_Ammophila
sabulosa_, Fig. 89), buries caterpillars; the =Path Wasp= (_Pompilius
viaticus_), spiders; the =Weevil-killing Sand Wasp= (_Cerceris
arenaria_) and the =Fly-killing Sand Wasp= (_Mellinus arvensis_)
respectively bury weevils and flies.
[Illustration:
FIG. 89.—The Common Sand Wasp (_Ammophila sabulosa_); natural size.
]
Family: =Formicidæ= (_Ants_).
Large strong mandibles adapted for biting; maxillæ and lower lip not
prolonged like a proboscis. Workers wingless; the males and reproductive
females have weakly veined wings. In correspondence with these facts,
the mesothorax which bears the larger wings is most strongly developed
in the last, but the prothorax in the workers. Abdomen united with the
thorax by a one- (_Formica_) or two-jointed (_Myrmica_) stalk. All
female ants, and naturally workers too, possess poison-glands, the
secretion of which accumulates in a poison-bladder; but the sting is
lacking in all species of _Formica_. The stingless ants (_e.g._ the Red
Wood Ant, _F. rufa_) inflict a wound with their strong mandibles, and
then, bending the abdomen forwards under the thorax, squirt the contents
of the poison-bladder into the wound. Ants form colonies, always of
large size, and consisting of reproductive and sterile individuals.
Their food is both of animal and vegetable nature, but chiefly consists
of insects and similar small animals. They mostly devour caterpillars,
but also dead or wounded beetles (_e.g._ cockchafers), mammals, birds,
and reptiles. As destroyers of caterpillars they are of use, but this is
true more of those living in woods than those which inhabit fields and
meadows. Ants are fond of all sweet substances; when they enter houses
the sugar jar is very often the end they have in view. They are
particularly fond of licking up the sweet juice which aphides excrete
from their abdomens. On plants infested with aphides many ants are found
which greedily sip up all the drops hanging from the abdomens of the
aphides; they may even promote the shedding of the juice by stroking the
abdomens of the little animals with their antennæ. There are, indeed,
species of ants which carry the aphides to the plant parts on which they
thrive best, and again, when these are sucked dry, transport them to
other uninjured parts. Sometimes aphides are kept in the overground or
underground nests of the ants. The common yellow meadow ants shelter
aphides in their subterranean nests, where they live on the roots of
grasses and other plants. In order to get, when necessary, fresh food
for these “milch kine,” they occasionally enlarge the nest, so that new
plant roots are laid bare, and they then carry the aphides to these.
During the greater part of the year only workers, larvæ, and pupæ are
found in an ants’ nest, but reproductive individuals appear in summer,
disappearing again before the cold weather comes on. As soon as there is
a sunshiny day they fly out, usually in large numbers. After pairing,
the females let themselves fall to the ground; they then either tear off
their own wings or this is done for them by the workers, which search
them out and take them to the nest, where the laying of eggs quickly
begins. The legless larvæ have feebly developed mouth-parts, and are fed
by the workers on food broken down by them. The pupæ vary; in the
sting-bearing ants (_Myrmica_) they are naked, in the stingless ants
(_Formica_), on the other hand, they are invested in a cocoon. The
latter kind of pupæ, known by the incorrect name of “ants’ eggs,” are
collected and used as food for insect-eating birds. The nests are made
either out of pine-needles and small branches heaped together (=Red Wood
Ant= = _Formica rufa_), or they eat out passages and cell-like spaces in
sound tree trunks (the larger =Wood Ants=, e.g. _F. herculeana_ and _F.
ligniperda_) or in decayed tree trunks (=Small Wood Ant= = _F.
fuliginosa_); others (=Yellow Wood Ants= = _F. flava_, etc.) make
passages and cavities in the ground, throwing up the earth into
ant-hills. _Damage_: Several species do harm by excavating the soil,
either in meadows and cornfields, by which the plants are killed and
harvesting rendered difficult, or under summer-houses and
dwelling-rooms. Others destroy tree stems. They are indirectly harmful
on account of the way in which they care for aphides, causing these
pests to increase to a greater extent than would otherwise be the case.
_Remedies_: If ants have got into a room the nest must be found if
possible, and the insects there destroyed with paraffin or boiling
water. If it proves to be too difficult to find and destroy the nest,
all the openings by which the ants can enter must be stopped up with
lime to which some extract of colocynth has been added. The nests found
in fields and gardens may sometimes be destroyed by quickly digging them
up, pouring paraffin over them, and then igniting it. It is also a good
plan to frequently tread or roll down the ant-hills which are thrown up,
as in this way they will be dispersed in the end. Ants are of service in
forestry, but scarcely in agriculture.
Family: =Ichneumonidæ= (_Ichneumon Flies_).
The species of ichneumon flies deviate in many ways from one another,
but they all have similar habits and play a similar part in nature. They
all have a longer or shorter ovipositor, always surrounded by two flaps,
and serving for laying eggs in other animals. Those which seek their
prey in branches and leaves generally possess a very short ovipositor
not obvious on cursory examination; those which lay their eggs in
insects inhabiting crevices, _e.g._ wood insects, are often provided
with a very long ovipositor. No colonies and, consequently, no workers.
The female ichneumon fly generally lays her eggs in the body of an
insect larva, on which the ichneumon larvæ developed from these eggs
feed, using up the reserve matter stored up in the fat body (p. 92).
Caterpillars are most infested; then follow false caterpillars, and then
the larvæ of weevils and leaf beetles. The eggs of a few kinds are laid
in pupæ, or even in the eggs of moths and butterflies. They always
select for this purpose those insects which possess reserve material.
The large kinds of ichneumon fly lay only a single egg in one host,
especially if the latter is not of large size; many of the smaller
ichneumons, on the other hand, lay many eggs (Fig. 90) in one host, even
up to a hundred or more. A caterpillar containing ichneumon eggs does
not at first appear different from other caterpillars, except that a
dark spot or patch usually indicates where its body was pierced by the
ovipositor of the ichneumon fly. The parasite breathes while in the host
by bringing the tip of its abdomen (where the main stem of the air-tube
system opens) into connection with one of the host’s spiracles. Since
the larva feeds altogether upon perfectly digestible substances an anus
is superfluous and is absent. Many ichneumon larvæ are ready to become
pupæ when the host is about to pass into the same condition; the larva
then bores through the skin of the latter, which quickly dies. Other
species do not attack the organs of the host so soon, but allow it to
become a pupa in peace, and then themselves become pupæ inside it; later
on, one or several ichneumon flies come out of this pupa instead of a
moth or butterfly. It is obvious that ichneumon flies are very
serviceable by destroying a large number of harmful insects. They
cannot, indeed, prevent the increase of any particular noxious insect,
but, when this takes place, they themselves increase to a greater
extent, and finally appear in such numbers as to make an end of the
pest.
[Illustration:
FIG. 90.—The Yellow-legged Ichneumon Fly (_Microgaster glomeratus_) of
the Cabbage Caterpillar. Left, the adult insect; right, the larva
(both enlarged). In the middle, Cabbage Caterpillar and a heap of
Microgaster pupæ.
]
I shall not enumerate here all the various ichneumon flies which benefit
agriculture, but simply mention the =Small Cabbage Caterpillar Ichneumon
Fly= (_Microgaster glomeratus_), depicted in Fig. 90, which, like its
host (the large cabbage white), appears in two generations. The larvæ of
the ichneumon fly live in large numbers in the large cabbage
caterpillar, and at their last moult acquire minute teeth, with which
they bite through the skin of their host; they then leave it to die, and
surround themselves with a cocoon close to its dead body. There are,
besides, a few small and also some large ichneumon flies which lay their
eggs in the pupæ of the cabbage white, so that, _e.g._, in winter many
of its angular pupæ, occurring on tree stems and hedges, are found with
many small or several large white ichneumon larvæ within them.
Family: =Tenthredinidæ= (_Saw_-_flies_).
Body thick-set. Abdomen never very long, and united by a broad base to
the thorax (Fig. 91). Saw-shaped ovipositor (p. 89), drawn in when not
in use, and only protruded during egg-laying. Mandibles strong, the
remaining mouth-parts not so well developed. The larvæ are false
caterpillars (p. 92); they can usually be recognized by their
characteristic attitude, for many of them bend the abdomen very much
upwards and forwards, especially when frightened, and when at rest the
hinder part of the body is spirally coiled (Fig. 91). The fully
developed larva spins a cocoon in which it still remains for a long time
in the larval condition, even during the whole winter. It becomes a pupa
two or three weeks before the appearance of the perfect insect. There
are many larvæ of this kind destructive to woods, but only a few which
interest the farmer. Here is included—
The =Turnip Saw-fly= (_Athalia spinarum_).
_Adult_: Female one-third of an inch long, stretch of wing over
two-thirds of an inch; male somewhat smaller. Bright orange or reddish
yellow. Head black, thorax and legs with black markings. Wings large.
_Larva_: Length may be rather more than two-thirds of an inch. The
just-hatched larvæ are almost colourless, but the skin quickly becomes
bright green, and after the first moult, dark green to black. Ventral
side slate grey. Head shining black. Twelve broad body segments, upon
which are many wrinkles of the skin.
[Illustration:
FIG. 91.—The Turnip Saw-fly (_Athalia spinarum_): adult female and two
caterpillars.
]
The sluggish adult is found, during May or August, upon kohl rabi and
turnips, mustard and charlock, with its wings folded together. The
female, by means of her ovipositor, saws small holes in the margin or
under side of the leaf, and lays her eggs in these. The larvæ are
hatched in from four to six days, and they undergo four moults. The
presence of the larvæ can be detected by their cast skins, which remain
sticking to the leaves even when the animals themselves, which are often
found rolled up on the under sides of the leaves, cannot be seen. The
enemy is also known by its way of feeding, for the larvæ keep on the
surfaces of the leaves (upper or under surface) and eat out longish
holes. As soon as these have reached a certain size, other parts of the
leaves or other leaves are attacked. When the larvæ are numerous the
holes continually increase in number until only the leaf-ribs are left.
The mature larvæ creep into the soil to a depth of from two-fifths to
four-fifths of an inch, and spin a small cocoon. The saw-fly emerges
either the same or the following year. These insects may therefore
appear in May or in August, but in many cases they are seen at only one
of these times, either the summer or autumn turnips being attacked, as
the case may be. _Remedies_: Fowls and ducks willingly eat the larvæ,
and, provided they are not able to do any damage, can therefore be
brought into the fields. Strewing with soot has a good effect. It pays
to pick off the larvæ from young plants.
ORDER 5: =Lepidoptera= (BUTTERFLIES AND MOTHS).
[Illustration:
FIG. 92.—Head of a Butterfly. A, eye; _Fh_, antennæ; Z, proboscis.
]
[Illustration:
FIG. 93.—Scales from a Butterfly’s Wing (strongly magnified).
]
Sucking mouth-parts, forming a “proboscis” made up of the two very long
maxillæ, spirally rolled up under the head when not in use (Fig. 92),
and adapted for sucking honey. There are some forms which take no food
in the adult condition, and in which the proboscis is short; in a few
species of hawk-moths, this organ is even longer than the body. The
larvæ (“caterpillars”) have biting mouth-parts. The body of a butterfly
or moth is covered with hair-like structures developed by the skin; in
the wings these are broader, have a characteristic appearance (Fig. 93),
and partially overlap one another. These scales cause the colours of the
wing. They can easily be wiped off, leaving the corresponding part of
the wing transparent and clear as glass. In many species (all
hawk-moths, many owlet moths) there is a _wing-hooklet_, i.e. the hind
wing has a spine or a thick brush which grasps a band-like area of the
fore wing. In this way the two pairs of wings are held together. The
females of a few species of spinner and looper moths are wingless, or
only possess short flap-like wings useless for flight. The metamorphosis
is complete (p. 89); the larvæ are true caterpillars; the pupæ are
obtectate (p. 93). Many caterpillars creep into the ground to become
pupæ, and spin no investment at all (_e.g._ hawk-moths). Others make a
cocoon, which may consist of threads loosely woven together or may be of
firm texture (Fig. 60). The cocoon consists chiefly of silk, a substance
secreted in a spinning gland, and exuding to the exterior on the lower
lip; but minute particles of sand or earth, and fragments of wood gnawed
off by the caterpillar, may be stuck in the cocoon. The pupæ of
butterflies are naked, without cocoon, but are fixed by threads to
leaves, tree stems, walls, hedges, etc. A distinction is drawn between
girdled and suspended pupæ; the first are fixed by a silk band, which
surrounds them, and the head is directed upwards, while the latter are
suspended by the tip of the abdomen (Fig. 94). The time required for the
development of the perfect insect from the pupa is not always the same,
depending not only upon the species, but also upon the time of year. The
summer generation of the large white spends scarcely fourteen days in
the pupa stage, the winter generation eight months.
Family: =Diurna= (_Butterflies_).
Body relatively weak and thin; wings very broad, not very long
relatively. No wing-hooklet (_see above_). Wings folded together above
in a state of rest, so that their upper sides touch. Antennæ thickened
in a club-like way at the tip. The caterpillars possess five pairs of
pro-legs; they are usually almost devoid of hair. There are, however, a
few (_e.g._ the caterpillar of the peacock butterfly, Fig. 94) which
possess hard, spine-like, much-branched bristles. The naked pupæ are
sharp cornered; some are girdled, others suspended (p. 137).
[Illustration:
FIG. 94.—The Peacock Butterfly (_Vanessa io_), with pupa, and larva
suspended before passing into the pupa state.
]
Among butterflies with larvæ that become suspended pupæ are the =Red
Admiral= (_Vanessa atalanta_), the =Peacock= (_Vanessa io_, Fig. 94),
the =Fritillaries= (_Argynnis_), the =Meadow Browns= (_Hipparchia_),
etc.; and among those with girdled pupæ the =Swallow Tail= (_Papilio
machaon_), the =Whites= (_Pieris_), etc.
The =Cabbage White=, or =Large White= (_Pieris Brassicæ_).
_Butterfly_: Length a little over an inch, span of wing 2½ inches. Both
fore and hind wings milky white, the former black at the root, on the
front edge, and the outer angle; also a black patch on the inner margin
of the fore wing, passing on to the front margin of the hind wing. The
female possesses, in addition, two round black patches on the middle of
each fore wing. Under side of the fore wings milky white, yellow at the
tip, blackish at the root; under side of the hind wings yellow, with
black dots. _Caterpillar_ (Fig. 95): As much as 1⅓ inch long; greenish,
or sulphur yellow, with black dots. Head and dorsal side of last segment
of the body grey with black spots. Young specimens are of a very bright
green with black wartlets closely crowded together.
[Illustration:
FIG. 95.—The Cabbage White (_Pieris brassicæ_) female laying her eggs;
caterpillar, and pupa.
]
From the pupæ which have lived through the winter butterflies emerge in
May, and lay their golden yellow eggs in small heaps on the under sides
of the leaves of rape, mustard, and cress, also on charlock and
such-like cruciferous weeds. The caterpillars of this first generation
are hatched in fourteen days, and rarely do any harm, since they only
appear in small numbers. They develop rapidly, and during the last days
of June become pupæ on the branches and leaves of the plants they live
on; the butterflies appear in July. Owing to their rapid development the
caterpillars and pupæ of this first generation are but little exposed to
the attacks of enemies (ichneumons, birds, etc.). Only a few of them
die, therefore, if the weather is favourable. As a result of this, the
July butterflies and the eggs laid by them are relatively numerous, so
that the number of caterpillars appearing in late summer may be very
large. These caterpillars, however, live almost exclusively on the
various kinds of cabbage and kohl rabi, and it is this second generation
which in many years is so harmful. At the beginning of August the
caterpillars are ready to become pupæ, and for this purpose they seek
tree stems, hedges, walls, etc. The pupæ now formed live as such through
the winter. During this period, however, they are exposed to many
dangers (damp, cold, sudden alternation between very low and very high
temperatures; ichneumons, birds), and most of them perish, so that only
a few butterflies come out the following spring, and lay but a few eggs.
It is therefore obvious that the first generation of caterpillars (May,
June) is much less numerous than the second generation occurring from
late summer to autumn. Under exceptionally favourable conditions even a
third generation may appear, since caterpillars of the second generation
are able to become pupæ at the beginning of August; and these pupæ,
instead of remaining as such over winter, become butterflies the same
month. These, again, lay eggs from which the caterpillars of the third
generation are hatched, which, however, are not always fully developed
before the advent of the cold weather, and in this case perish. It is
clear that, in the case of pupæ which develop into butterflies during
August in about fourteen days, the unfavourable influences have either
no effect (unfavourable weather) or but little (ichneumons, birds), so
that the butterflies appear in flocks, which wander into other regions,
since they have themselves, when larvæ, devoured the cabbage and turnip
plants. In reference to the damage effected by the caterpillar, it may
be observed that only the chief veins of the leaf are left, and the
margins are not spared. _Remedies_: Collection of the little heaps of
yellow eggs and the young caterpillars, which are blackish and live
together in small companies; the planting of a few small hemp plants in
the cabbage fields to be protected, by which the butterflies will be
kept away.
The =Garden White=, or =Small White= (_Pieris rapæ_).
[Illustration:
FIG. 96.—The Garden White (_Pieris rapæ_), male.
]
[Illustration:
FIG. 97.—The Garden White (_Pieris rapæ_), female, caterpillar.
]
_Butterfly_ (Figs. 96 and 97): Length rather less than an inch, span of
wing two inches; very much like the cabbage white. Base and tip of the
fore wing not of such a deep black colour; the black patch in the inner
margin of the fore wing is usually absent in the female. The male,
however, very often has a black patch in the upper side of the fore
wing. _Caterpillar_: Just over an inch long. Dull green; a longitudinal
yellow line on the back; also the black stigmata are connected by a
yellow line. Habits as in the preceding species; the female, however,
lays her yellow eggs separately, and not in heaps, and the second
generation of caterpillars usually become pupæ somewhat later in the
year. Collecting is more difficult than in the preceding species, since
the young caterpillars live independently, and their colour makes it
difficult to recognize them on the green cabbage leaves.
The =Green-veined White= (_Pieris napi_).
_Butterfly_ (Fig. 98): As large or somewhat smaller than the preceding
species. Wings milky white on their upper side; fore wings dusted with
black on their front margin, tips, and ends of the ribs. Two spots on
the middle of the fore wing in the female, one or none in the male.
Under side of the hind wings yellow; under side of the veins dusted with
greenish grey. _Caterpillar_: A little over an inch. Dull bluish-green,
with minute blackish tubercles above, and whitish ones below. A yellow
longitudinal line on each side connecting the black spiracles, which are
bordered by reddish yellow. Very like the preceding species in the
larval condition. Habits as in the preceding species, but this is less
common.
[Illustration:
FIG. 98.—The Green-veined White (_Pieris napi_).
]
Family: =Noctuidæ= (_Owlet Moths_).
Night-flying moths, of medium size and dull colour, with smooth-haired
bodies. Antennæ long and thin, thread like,—comb-shaped only in the
males of a few species; wings powerful, lie in a roof-like way when at
rest; almost always a wing-hooklet. Caterpillars usually hairless;
mostly with five pairs of pro-legs, a few with four or three pairs. The
owlets pair at night; they also fly about during the day, even in bright
sunshine. Flight strong and rapid, but always in fits and starts. Almost
all species lay their eggs separately, and on herbs, only a few species
on trees. The caterpillars are very much scattered, and the damage
caused by them is never great, except in spots here and there,—on the
contrary, when they increase to a great extent they spread over a wider
area. Several species are harmful to agriculture.
The =Surface Caterpillars= (Species of _Agrotis_)
are stout caterpillars, 1⅕ to 2 inches long, with five pairs of
pro-legs, and shining transparent external skin. They remain in the
ground during the day, feeding above ground at night, and also in the
daytime when the sky is much overcast. When touched they bend themselves
into the form of a C. There are in Britain several species of surface
caterpillars which have these habits, but I will only describe here, to
begin with, the commonest kind:—
[Illustration:
FIG. 99.—The Common Dart or Turnip Moth (_Agrotis segetum_) with
Caterpillar.
]
The =Common Dart= or =Turnip Moth= (_Agrotis segetum_ or _A.
clavis_).—_Moth_ (Fig. 99): Length almost ⅘ of an inch. Span of wing
about 1⅘ inch. Fore wings small, ash-grey or brownish, with many dark
patches and similar markings. Hind wings in the male, bright grey to
snowy white; in the female, brownish grey. _Caterpillar_ (Fig. 99): Up
to two inches, earthy grey, occasionally somewhat greenish. Head and
prothorax darker. The time taken by the caterpillars to complete their
development differs according to the plants attacked, and it is
therefore easy to understand why the moths should be seen flying about
from the first half of May right on into the autumn, without having
recourse to the improbable hypothesis of two successive generations. The
eggs are consequently laid at very different times, and are always
deposited singly in the soil in the neighbourhood of plant roots, or
else in the low-lying leaves and stems of various herbs. The
caterpillars hatched from these are destructive earlier or later,
according to the time of egg-laying. Most specimens are half grown in
winter; these continue their destructive work the following spring. In
autumn they attack the roots of winter grain (rye and wheat), rape, and
species of cabbage; they also bore readily into turnips and potatoes. In
spring, after the winter rest, they continue to attack the roots of
winter grain, winter rape, etc., or fleshy underground parts (turnips,
potatoes) developed in the interim, or the roots of summer plants
(summer grain, buckwheat, summer rape, vegetables, etc.). On clear days
the caterpillars always remain hidden in the soil; and those which have
bored into juicy underground parts of plants (turnips, carrots), do not
leave their abode during the day, but the others, both during the night
and on cloudy days, come above ground to attack the leaves and stems of
young plants. In exceptional cases the caterpillar is mature by the
beginning of winter, in which case it hybernates in the soil as a brown
pupa. The moths escaping from such pupæ naturally appear earlier than
others. As a rule, the caterpillars do most damage to the winter crop in
autumn, wandering about a great deal; in many cases they gnaw through
the main root, thus quickly killing the plant attacked, from which they
proceed to another. _Remedies_: When the caterpillars have done much
damage in late summer, it is recommended to leave the field alone till
October, then to plough it up and sow the winter grain. By putting off
the seed-time in this way, the caterpillars will have lost their
activity when the corn germinates, and the winter crop will thus escape
them. Besides this, the preceding ploughing will bring many caterpillars
to the surface, where they will become the prey of birds, or, if not,
can be collected. Warm soils, especially those manured with horse dung,
are most infested by the caterpillars; and the use of warm kinds of
manure should, therefore, be avoided in regions which have much to fear
from these insects. Where everything has been destroyed, a thorough
ploughing is desirable. Swine may also be driven in during autumn, and
will grub up and devour the caterpillars. In this case, sowing will take
place the following spring.
Other _Surface Caterpillars_, which have pretty much the same habits as
the preceding, are those of the =Heart and Dart Moth= (_Agrotis
exclamationis_), the =Wheat Moth= (_A. tritici_), and the =Thick-bodied
Surface Caterpillar= (_A. ravida_ or _A. crassa_).
The =Cabbage Moth= (_Mamestra brassicæ_).
_Moth_ (Fig. 100); about ¹¹⁄₁₂ of an inch long, span of wing 1⅗ inch.
Fore wings shining brown, with yellowish and black marbling; each patch
having a dark outline; a yellowish zigzag line on the outer margin. Hind
wings shining yellowish-grey brown. A strongly developed crest in the
middle line of the thorax. _Caterpillar_ (Fig. 100): 1⅗ inches,
cylindrical. Bright or dark green, brownish green, or greenish brown. On
the back a dark longitudinal stripe, divided into two halves by a narrow
white longitudinal line. A whitish line running along each side; between
this and the dorsal line a dark transverse streak on each segment. The
brown pupa (Fig. 100) remains in the soil during the winter, and is not
invested in a cocoon. The moth appears in May; during the day it rests
on windows, in barns, etc. The greenish yellow eggs are laid separately
on the leaves of cabbages (sometimes also on lettuces and turnips). The
caterpillars, which appear in fourteen days, creep about actively
between the leaves. Within a month they are full-grown, and become pupæ
in the soil. At the end of July and in August the summer generation of
moths appears. From the eggs laid by these are hatched a second
generation of caterpillars, which are always much more numerous than
those of the first. From August to October they are found in all kinds
of cabbage, especially compactly headed kinds and cauliflower. At first
they eat holes in the leaves, leaving, however, the chief veins and
usually the edges. Later on they eat right on into the heart of the
cabbage. They fill their burrows with excrement, and the attacked plants
begin to rot internally. The full-grown caterpillars creep out and
become pupa in the soil. _Remedy_: Collecting the caterpillars while
they are still on the outer leaves.
[Illustration:
FIG. 100.—The Cabbage Moth (_Mamestra brassicæ_), with caterpillar and
pupa.
]
The =Vegetable= or =Lettuce Moth= (_Mamestra oleracea_).
_Moth_: ⅗ of an inch long; span of wings about 1⅖ of an inch. Fore wings
dark rusty brown, darker on the nerves, dusted with white. Hind wings
reddish white. Head and thorax like the fore wings; abdomen like the
hind wings. _Caterpillar_: Up to 1⅗ inch; dirty greenish grey, or olive
green, irregularly bestrewn with dirty white dots. The caterpillars feed
on cabbages, lettuce, asparagus, and other vegetables. Those of the
first generation (June and July) hollow out lettuce stalks before the
head begins to be formed; those of the second generation (August and
September) feed on cabbage or asparagus leaves. The first generation of
moths appear in May, the second in the first half of August.
The =Pea Moth= (_Mamestra pisi_).
_Moth_: About ⅖ of an inch long; span of wings about 1⅖ of an inch. Fore
wings bright reddish brown with bluish-grey markings, and a yellowish
longitudinal streak. Hind wings reddish grey. _Caterpillar_: 1⅘ of an
inch; cylindrical; slender. Back dark greenish or brown red; closely and
tolerably regularly veined with dark lines, and with two sulphur yellow
longitudinal streaks on the back and one on each side. Head, belly, and
feet flesh red. If the caterpillar is touched it moves the front part of
its body about here and there, and then lets itself fall down. The moths
appear in May and June; the caterpillars are found from July to
September on peas, vetches, beans, clover, lupins, sorrel, orach, heath,
willow, birch, and yet other plants. Seldom very destructive.
The =Grass-root Moth= (_Hadena monoglypha_, or _H. polyodon_).
_Moth_: About ⅝ of an inch long; span of wing 1⅘ inches. Fore wings
longish; yellow brown blended with dark brown and white; the tips are
coloured most brightly. Three black rays on the fore wing; hind wings
brown grey. _Caterpillar_: About 1⅗ inches long, ⅓ of an inch broad,
with sixteen feet. Grey or reddish white, more or less shining. Head,
prothorax, the last body segment and warts black. At the end of July and
during August the female lays her eggs separately on the bases of grass
haulms and leaves. The caterpillars creep out at the end of August, and,
especially after their hybernation (in April and May), attack meadow
grasses, biting through the leaves and haulms at their bases,
immediately above the surface of the ground, and devouring, as it were,
passages through the grass. The reddish brown pupæ rest in the soil.
The =Couch-grass Moth= (_Hadena basilinea_).
_Moth_: Nearly ⅘ of an inch long; span of wings 1⅗ inches. Head and back
rust-coloured or reddish grey, in the male with a large tuft of hairs.
Fore wings coloured like the back, with two transverse lines in the
middle, and brighter and darker marks as well. Hind wings bright brown,
with a faint golden sheen, and with a yellowish fringe. _Caterpillar_:
1⅕ to 1⅖ inches long, with sixteen feet, bluish grey, somewhat brownish,
with dirty white longitudinal lines; greenish belly, and large bright
brown head. The moth lays the eggs in little heaps on the stems and
leaves of grass plants. The damage which the caterpillars effect among
meadow grasses is inconsiderable; but they sometimes appear in
considerable numbers on grain-plants, and are then very destructive. The
insects are chiefly found on dry high-lying land, which is consequently
most liable to the attacks of their larvæ. After hybernation they feed
on grass or the leaves and stems of young grain-plants, and change in
the soil into stout, smooth, yellowish-brown pupæ, devoid of cocoon.
_Remedy_: In case the caterpillars have got into the crop, threshing
should take place as soon as possible, or, after hybernating, they will
continue to devour the grain in the barns.
The =Wheat-haulm Moth= (_Luperina didyma_).
_Moth_: Span of wing 1⅕ inches. Individual specimens differ very much
from one another: brownish, greyish yellow to ochre yellow, with various
dark and light markings. _Caterpillar_: With sixteen legs, and over an
inch long in full-grown specimens (May); thin, spindle-shaped; stiff;
bright shining green, with two broad dark red lines on the back. The
caterpillars live in the stalks of wheat plants, and other gramineous
forms, hollowing them out; they hybernate when tolerably young. In
spring they continue to hollow out the wheat plants, going from one
stalk to another. The plants attacked quickly have their leaves turned
to a rusty colour, and they sicken or even die.
The =Grass Moth= (_Charæas graminis_).
_Moth_: Length ⅗ of an inch; span of wings about 1⅓ inches. Antennæ of
the male comb-like. Fore wings short, of a brownish-red, olive brown, or
dirty olive-green ground colour, with three whitish patches, and darker
markings. Hind wings yellowish grey, brighter at the roots.
_Caterpillar_: With sixteen legs; 1⅘ inches long; bronze grey, back more
of a bronze brown, with three narrow bright longitudinal streaks. Head
ochre yellow. The moth lays her some two hundred eggs during July, in
little heaps at the bases of the grass haulms and leaves. The
caterpillars hide during the day, and feed at night. They are very
injurious even in the autumn, but become insatiable the following
spring, always devouring the lowest parts of the haulms and leaves, so
that the upper parts die off. They wander in large companies from one
field to another. In June they become pupæ of a shining reddish brown
below the surface of the soil or under sods. _Enemies_: swine, moles,
shrews, rooks, wagtails, ducks, fowls. _Remedy_: Driving in swine, where
this is practicable.
[Illustration:
FIG. 101.—The Grass Moth (_Charæas graminis_) and its caterpillar.
]
The =Darnel Moth= (_Neuronia popularis_).
_Moth_: Length rather less than ⅘ of an inch; span of wings nearly 1⅗
inches. Much variegated, beautiful. Fore legs reddish brown, with
peach-coloured glow; all the nerves and several markings yellowish
white, and dark markings as well. Hind wings yellowish, and abdomen
white. Head and thorax brown, mixed with yellowish white. _Caterpillar_:
Over two inches long, and about one-third of an inch thick; 16-legged;
tapers at both ends. Has an oily lustre. Dorsal side of a bronze brown,
sharply marked off by a yellowish line from the bright brownish grey
ventral side, and traversed by three longitudinal bright brown lines,
which in young specimens are almost white. Habits pretty much like those
of the preceding species.
The =Silver Y Moth= (_Plusia gamma_).
[Illustration:
FIG. 102.—The Silver Y Moth (_Plusia gamma_), with caterpillar and
pupa.
]
_Moth_: About ⅝ of an inch long; span of wings 1¾ inches. Dark grey,
mixed with a reddish tint, and darkly marbled. About the middle of the
fore wing there is a very obvious gamma (γ), or Y-shaped mark. Hind
wings bright brown at the root, darker at the margins, with a whitish
fringe. A crest of hairs on the dorsal side of the thorax.
_Caterpillar_: 12-legged. It bends its body like a looper (Fig. 102).
Length 1 to 1⅕ inches. Ground colour green; but there may be variations
in this from a dirty green to a brownish colour. Six fine longitudinal
lines on the back, and a yellowish line above the legs. The caterpillar
is almost naked, only possessing a few small, isolated bristle-like
hairs. _Habits_: At least two generations, and sometimes as many as five
in two years. The Silver Y Moth generally hybernates as a half-grown
caterpillar, but sometimes also in the pupa, or moth state. The
caterpillars may therefore be met with the whole year; but they are
usually most abundant from the end of June to the middle of August, and,
under favourable conditions, may become an agricultural pest. They
devour the leaves of almost all wild and cultivated plants (except
grasses, corn, and trees), and are especially fond of leguminous plants
(peas, vetches, clover), flax, beet, rape, cabbage, and buckwheat. The
moths mostly appear in May, but also in July, and later on in the
summer, especially on clear days. The female lays her numerous bright
green eggs, some four hundred in number, separately, on the leaves of
the above-named plants. The caterpillars are not always easy to see,
owing to their greenish colour; under favourable conditions they may
pass through the whole of their development up to the moth stage in from
six to seven weeks. In some years they appear in such large numbers,
that almost all the cultivated plants found in the fields of an infested
region are utterly spoilt by them, excepting the corn. _Natural
enemies_: Starlings, all sharp-beaked singing birds haunting fields;
sparrows; ground beetles, rove beetles, and the larvæ of these families;
several ichneumon flies, parasitic fungi. _Remedies_: Driving in
poultry, where practicable. Collecting, _e.g._ by means of a machine
invented by L. Dehoff, of Gutenberg, near Halle. “Several troughs with
steep inner walls are fastened together by laths, at distances equal to
those between adjacent furrows, and besoms are fixed to the laths. These
troughs are drawn along like sledges by a horse walking in the furrows,
and the caterpillars are swept by the besoms into the troughs, from
which they are collected in sacks at the ends of the furrows. With this
cheap machine about twelve acres per day can be cleared” (Taschenberg).
Family: =Pyralidæ= (_Snout Moths_).
Small moths with thread-like antennæ, comb-like in the males of a few
species, with tolerably large eyes, and very large labial palps often
stretched out in front like a beak (Fig. 103). Fore wings of an
elongated triangular shape. Wing booklets. Legs tolerably long.
Caterpillars slightly hairy, with four or five pairs of pro-legs.
The =Rye Snout Moth= (_Pyralis secalis_).
_Moth_: ⅗ of an inch long, span of wings 1⅕ inches. Wings elongated,
whitish grey, with an A-shaped patch on the fore wings. _Caterpillar_:
Rather more than ⅖ of an inch long; green, streaked with brown,
16-legged, with a brown head, and tapering at both ends. _Habits_: The
caterpillar lives during June in the rye haulms, hollowing them out. As
a result of this, the ears remain hidden between the leaves and
leaf-sheaths, and it often happens that only the tips of the awns appear
externally. No grain is formed; the ears first become white and dry, and
then fall off.
The =Hop Snout Moth= (_Hypena rostralis_).
[Illustration:
FIG. 103.—The Hop Snout Moth (_Hypena rostralis_).
]
_Moth_ (Fig. 103): Length rather less than ⅖ of an inch; span of wings
1⅕ inches, or more. Fore wings usually brownish, somewhat scalloped on
the fringed outer margins; a zigzag black line near the base; in the
middle, near the front edge, a patch bordered with white, and behind
this a dark longitudinal streak. Hind wings dull grey, with a silky
sheen. _Caterpillar_: At most one inch long, 14-legged, very slender,
green, with a dark middle line and two white side lines. Very active;
wriggles about on the ground like an eel. _Habits_: The moth is on the
wing at the beginning of August, the second generation in August; the
latter hybernates in outhouses, barns, summer-houses, etc. The eggs are
laid on wild and cultivated hops, also on stinging nettles. The
caterpillars are found on the hop plants, especially in June; they
sometimes entirely devour the leaves, with the exception of the nerves.
In July they become pupæ, either between the leaves or on the soil, and
are invested in a grey cocoon. The moths appear at the beginning of
August, and give rise to a second generation of caterpillars, from
which, after the pupa stage, the moths which live through the winter are
developed.
The =Cabbage Snout Moth= (_Botys forficalis_).
_Moth_: Length about half an inch. Span of wings rather over one inch.
Fore wings sharply bent in front before their sharp tips; rusty yellow,
somewhat darker on the nerves, with rusty brown transverse streaks from
the outermost corners to the middle of the hinder margin, and with other
reddish brown markings. Hind wings and body shining straw yellow.
_Caterpillar_: ⅘ inch long, 16-legged, tapering in front and behind.
Yellowish green, with indistinct longitudinal lines and bright brown
head. A few small yellowish-green hairs. _Habits_: The first generation
appear in small numbers in May. The caterpillars hatched out from the
eggs of these live (May and June) on the leaves of cabbages and wild
cruciferous plants. They always shelter themselves between the leaves,
and spin a few thin threads across the entrances to their abodes. The
caterpillars burrow horizontally in the earth, and there become pupæ
invested in cocoons. The moths of the second generation appear in
August; in autumn the caterpillars hatched from their eggs damage
cabbages, sometimes to a large extent. In October they burrow into the
soil, where they hybernate. _Remedy_: Deep digging or ploughing after
the crop, by which the larvæ invested in webs are buried deeply, and
consequently for the most part killed.
The =Mother-of-pearl Moth= (_Botys margaritalis_ = _B. extimalis_).
_Moth_ (Fig. 104): Length nearly ⅖ inch; span of wing over 1⅕ inches.
Fore wings bright sulphur yellow, with large rust-coloured patches, and
two rusty yellow transverse lines. Hind wings shining straw yellow; all
four wings with a mother-of-pearl sheen. _Caterpillar_ (Fig. 104): ⅘
inch, 16-legged, yellowish, head and neck-shield black. Body with a
broad, grey, longitudinal streak on each side. Four longitudinal rows of
dark brown warts. _Habits_: The moth is on the wing in June and July,
and lays the longish ovoid eggs on cruciferous plants (rape, radish,
several wild forms). The caterpillar lives concealed in a white web, and
gnaws holes in the pods, into which it inserts the forepart of its body
for the purpose of devouring the still green seeds. The attacked pods,
owing to the presence of round holes in them, look something like flutes
or fifes.
[Illustration:
FIG. 104.—The Mother-of-pearl Moth (_Botys margaritalis_), with larva
(1) and injured pods.
]
The full-grown caterpillars burrow into the soil, where they hybernate
in a delicate web. _Remedy_: Compare the preceding species.
Family: =Tortricidæ= (_Leaf-rollers_).
Small, thick-set moths (Fig. 105), with smaller palps than the snout
moths. Fore wings broad at the root, with straight or somewhat curved
outer margins. Hind wings as broad, or even broader, than the fore
wings. When at rest the fore wings lie in a roof-like way. They usually
possess many characteristic markings. Hind wings greyish, without
markings. Antennæ thread-like. Caterpillars hairless, or only slightly
hairy; 16-legged: many kinds live in leaves, which they roll up; others
in twigs, buds, and fruits, which they hollow out.
The =Fawn-coloured Pea Moth= (_Grapholitha nebritana_ = _G. pisana_).
_Moth_ (Fig. 105): Length ⅜ inch; span of wings about ⅖ inch. Fore wings
fawn-coloured, with metallic sheen; alternating short, white, and dark
lines on the front margin. Hind wings black, with bronze sheen and white
fringe. _Caterpillar_: ⅓ inch long; 16-legged; pale green, with brown or
black head, neck-shield, and last body segment. The thoracic legs are
black. Dark warts on each segment. _Habits_: Compare the succeeding
species.
[Illustration:
FIG. 105.—The Fawn-coloured Pea Moth (_Grapholitha nebritana_).
]
The =Crescent Pea Moth= (_Grapholitha dorsana_).
_Moth_: Somewhat larger than the preceding species. Fore wings olive
brown, with many small short white lines on the front margin. A
yellowish white crescent on the middle of the hinder margin. Hind wings
brownish. _Caterpillar_: Nearly ⅖ inch long, 16-legged, orange yellow,
with brown or black head, neck-shield, last body segment, and thoracic
feet. Covered with brownish-yellow warts. _Habits_: The moths fly about
in large numbers round the pea blossoms, always a short time after
sunset. The female lays one, two, or at most three eggs, on a very young
pod, or on an ovary. In fourteen days the caterpillar is hatched, bores
into the pod, and attacks the peas. The opening made in the margin of
the pod closes up again. The pod generally ripens early. When it opens,
the full-grown caterpillars creep out, and become pupæ in the soil,
within a web, where the pupa lives through the winter. The peas attacked
are always covered, while in the pod, with the coarse-grained excrement
of the caterpillars, and are often united two or three together by web
fibres. _Remedy_: Deep digging of the soil before the winter, or, still
better, deep hoeing as soon as the pea crop is gathered in. In this way
many of the caterpillars or pupæ hidden in the soil will be destroyed.
Family: =Tineidæ= (_Leaf-miners_).
[Illustration:
FIG. 106.—The Larch Moth (_Coleophora laricella_).
]
These moths are the smallest of the Lepidoptera. Like the snout moths,
they have strongly developed labial palps, but are distinguished from
them by their small wings; the hind wings are especially small, and have
sharp tips. The extent of the wings is increased by a broad marginal
fringe. When at rest, the wings slope like a roof, and the fringe near
their tips is often turned upwards. Antennæ thread-like, tolerably
long—in the males of a few species may even be very long. Caterpillars
slightly hairy, with five, or, rarely, four pairs of pro-legs. To this
family belong the well-known =Clothes Moth=; the =Corn Moth=, living in
stored-up grain; and also—
The =Carrot Moth= (_Depressaria nervosa_ = _Hæmylis daucella_).
_Moth_: Length ⅖ inch. Span of wings rather over ⅘ inch. Fore wings
reddish-grey brown, blackish on the nerves, and with scattered whitish
markings. Hind wings more of a grey brown. Thorax and abdomen very
shiny, and somewhat brighter than the wings. _Caterpillar_: Nearly ⅖
inch long, tolerably thick, especially in the middle, and variegated.
Head, thorax, and last body segment shining black, the last two regions
with reddish-yellow margin, and the thorax, in addition to this, divided
into right and left halves by a longitudinal yellow line. The rest of
the body is olive green; a broad orange-coloured line divides it into a
darker dorsal and a lighter ventral side. On the back many ill-defined
warts of a shining black colour. _Habits_: In March and April many of
the carrot moths which have survived the winter come out of their
hiding-places; they only fly at night. The eggs are laid separately on
umbelliferous weeds, carraway, or carrot plants. The caterpillars are
first seen when the plants flower; they live on the flower-stalks, which
they bind together by a few threads, and devour the flowers and young
fruits, sometimes even the flower-stalks. The caterpillars are very
active, and let themselves down by a thread when disturbed. Usually they
are fully grown in five weeks, and then bore into the stalks of the
plant, where they become pupæ. It is not known whether there are one or
two generations. The caterpillars are found at very various times, from
May to August.
The =Diamond-back Moth= (_Plutella cruciferarum_ = _Tinea xylostella_).
_Moth_: About ¼ inch long; span of wings ⅗ inch. Fore wings small,
lancet-shaped, with long fringes. Ground colour yellowish brown, darkly
speckled. Hind wings brownish grey, small, strongly fringed. When at
rest the long fringes form a sharp backward and upwardly directed comb,
while the antennæ are applied together and stretched straight forwards.
_Caterpillar_: About ¼ inch long, tapering in front and behind. A
beautiful green, with a black head. Lives hidden under a very thin web
or under a few fibres, on the lower side of the leaves of cabbage, rape,
and other crucifers. _Habits_: The pupa lives through the winter; the
moths emerge in May, and fly about in the evening. Two generations; the
first generation of caterpillars in the first half of July, the second
in late summer. The second generation is particularly apt to be
destructive to cabbage. Pupæ found on the leaves of the plants attacked,
and surrounded by a thick web.
SIXTH ORDER: Hemiptera (HALF-WINGED INSECTS).
[Illustration:
FIG. 107.—Left pair of wings of a Bug.
]
The mouth-parts are modified into a sucking and piercing beak. Head
small. Legs usually slender, with two- or three-jointed feet. Wings are
absent in several species (_e.g._ bed bugs); in one section (_e.g._
fruit bugs) the fore wings are half of leathery, half of membranous
texture (Fig. 107); in others, all four wings are membranous (winged
plant lice), or the fore wings are somewhat harder than the hind wings
(frog-hoppers). Incomplete metamorphosis (p. 89). None of agricultural
importance except—
Family: =Aphidæ= (_Plant Lice_).
[Illustration:
FIG. 108.—The Bean Aphis (_Aphis papaveris_); a larva of the same
below.
]
Long, five- to seven-jointed antennæ. Long thin legs, no power of
springing. Sucking beak long and thin. In the same species there are
both winged and wingless aphides, mostly the latter. In autumn, male and
female specimens are found. After pairing, the latter lay their eggs,
which are destined to live through the winter. The aphides hatched from
these the following spring are all females, but are distinguished from
those of the previous autumn by producing living young, which contain at
the time of their birth the germs of a new generation. The number of
young produced by a single female, and the number of generations
appearing within the year, vary according to the species. There are
species in which each female bears from eighty to one hundred young, and
nine to sixteen generations succeed one another in the year. In autumn
males and egg-laying females once more appear. As a rule the eggs live
through the winter, but the insects themselves may also do this. I must
add that there are constant differences within the boundaries of the
same species according to the habitat, and especially in the species
which regularly wander, either from one plant to another, or from the
leaves to the roots. But since the species injurious to agriculture do
not migrate in this way, nothing further need be said on the point. As
aphides suck plant juices during the whole of their lives, and have
enormous reproductive powers, they are very destructive. They suck from
stems and leaves the juices which would otherwise be used by the plants
themselves for growth or for the production of flowers and fruit, and
bear young, which bore their beaks into the same part in the immediate
neighbourhood of their mother, and quickly begin to multiply in their
turn. In this way, colonies consisting of a hundred or more individuals
are regularly formed (_e.g._ on peas, beans, roses). A plant part
attacked in this way shrivels for want of nourishment, and the aphides
upon it would die if they did not wander elsewhere. The third generation
usually contains, not only wingless individuals, but also others which,
after repeated moults, fly away and start a new colony in another plant.
Since aphides have many enemies (starlings, sparrows, grasshopper
warblers, etc., lady-birds and their larvæ, drone fly larvæ, lace fly
larvæ), and are often killed in large numbers by wind and rain, it only
occasionally happens, particularly in dry summers, that they entirely or
largely destroy the plants they infest. They injure plants, not only by
drawing away their nourishment, but also by the separation of a sugary
sticky fluid from the anus. If the minute drops of this fluid fall from
the upper parts of an infested plant to the lower (garden and field
beans), or from the leaves of an infested tree to the plants growing at
its foot, or, as sometimes happens, are carried by the wind to more
distant plants, great damage may be caused. The fluid evaporates and
leaves behind a shining sticky substance, which closes up the stomata of
the leaves, and partially checks exchange of gases (assimilation and
respiration). Particles of dust, sand, and smoke carried by the wind,
and also the cast skins of the aphides, stick to the surface of the
leaves and render exchange of gases still more difficult. The leaves
develop brown dirty patches, and die off. Besides this, the spores of
disease-producing fungi, carried by the wind, stick very easily to the
places covered by the sweet fluid, and readily germinate in it. Aphides
may thus be the indirect cause of several diseases (_e.g._ smut). These
insects are destructive, therefore, to other plants than those infested
by them. _Remedies_: Spraying with any one of the fluids destructive to
them—soapy water; a decoction of quassia chips; tobacco water, not too
concentrated; Nessler’s fluid (1½ ozs. soft soap, 2¼ ozs. tobacco
mixture, 2 ozs. fusel alcohol, half a pint ordinary alcohol, diluted
with rain water up to a quart: when used, mix with one-fifth the
quantity of rain water); Koch’s fluid (2 lbs. soft soap dissolved in
half a gallon of hot water; ½ lb. of quassia chips extracted for twelve
hours in 5 quarts of rain water, and the fluid thus obtained boiled and
filtered. It is then added to the soap water, and the whole brought up
to 10 gallons by addition of rain water). Spraying with one of the
above-named fluids must be renewed in a short time, so as to reach all
the aphides wherever possible; if even a few remain untouched, there
will soon be a large number again. A warm evening is best for the
spraying. Infested plants can also be strewn with finely powdered
substances, or these may be scattered over them by means of a small
bellows. Since such substances should remain on as long as possible,
they should be used after rain or early in the morning, when the dew is
still on the leaves. Among powdered matters suitable for the purpose,
the following may be named: gypsum, lime, tobacco, wood-ash, insect
powder (prepared from the flower-heads of Persian species of
chrysanthemum and from tansy heads). It must also be pointed out, that
these remedies must be employed as soon as the insects begin to show
themselves in considerable numbers; it is not desirable to delay till
the infestation has made considerable headway, as it is then much more
difficult to get a satisfactory result. In some cases, it is desirable
to cut off and burn or otherwise destroy much infested parts, or those
parts on which the insects first begin to multiply (_e.g._ early cutting
off of the tips of the stems in field and garden beans).
The species of aphis which most commonly occur upon cultivated plants
are:—The =Bean Aphis= (_Aphis papaveris_), ¹⁄₁₂ inch, black; on the tips
of the stems of field and marsh beans, also on poppy, turnips, lettuce,
and on several wild composites and umbellifers. The =Pea Aphis= (_Aphis
ulmariæ_), ⅛ to ⅙ of an inch long; green; July to September on peas,
chickling peas, and several wild leguminous plants; very destructive.
The =Corn Aphis= (_Aphis cerealis_), ¹⁄₁₂ inch, green or reddish brown,
also reddish brown with green abdomen; June to August on rye, barley,
oats and several grasses; sucks the axis of the ears, and the
flower-stalks; as the (black) eggs remain on the stubble during the
winter, it is advisable to plough this deeply in immediately after
harvest. The =Oat Aphis= (_Aphis avenæ_), ¹⁄₁₂ inch, dark green,
speckled with white; on oats and barley, scarcely ever on the ears, but
on the leaf-sheaths and the upper sides of the rolled-up leaves. The
=Hop Aphis= (_Aphis humuli_), ¹⁄₁₂ inch, green; on the under side of the
hop leaves, and, when very abundant, on the scales of the fruit. The
=Cabbage Aphis= (_Aphis brassicæ_), ¹⁄₁₂ inch, dark green, speckled with
grey; from May to September on all kinds of cabbage, and also on other
crucifers.
SEVENTH ORDER: =Physopoda= (BLADDER-FOOTED INSECTS).
Very minute insects, possessing a characteristic jaw apparatus, with
which they pierce the outer skin of leaves or the parts of flowers, and
suck their juices. The four small wings have long fringes at their
edges; the fore wings are tolerably hard. The ends of the feet do not
possess claws, but small bladders or suckers. The metamorphosis is
incomplete. In some years, one or other of the species may increase to a
very large extent, and these minute insects then fly about in swarms,
especially on very hot days; and they also wander about in large flocks.
If they settle on the face or hands of human beings, they cause a
disagreeable and persistent itching, as they continually walk about.
[Illustration:
FIG. 109.—Corn Thrips (_Thrips cerealium_).
]
The =Corn Thrips= (_Thrips cerealium_), ¹⁄₁₂ inch. Dark brown to black.
Male wingless. Female with small wings bending outwards at their tips
(Fig. 109); fore wings horny, hind wings membranous. Larva orange
yellow; head, prothorax, and tip of the abdomen, black. After the last
moult it becomes yellowish white, and acquires scale-like wings.
Hybernates in the adult condition; lays its eggs on various grasses,
also on different grain-plants. The larvæ, and, later on, the perfect
insects are found in large numbers sucking the ovaries of flowering corn
(wheat, rye, barley); as a result of which the ears do not fully
develop, but wither away. _Remedy_: Deep ploughing of the stubble, by
which the hybernating individuals are destroyed.
The =Elder Thrips= (_Thrips sambuci_) lives in elder, and sometimes also
multiplies in very young field beans, the leaves of which blacken and
shrivel up in consequence.
The =Flax Thrips= (_Thrips lini_) often injures flax.
EIGHTH ORDER: =Diptera= (FLIES).
Mouth-parts elongated, adapted for sucking or piercing. Fore wings
developed, rarely absent. Hind wings absent, as such,—altered into
club-like bodies (balancers or halteres) often covered with scales.
Metamorphosis complete. Larvæ always legless; most have biting
mouth-parts and no distinct head (maggots); the head-bearing dipterous
larvæ possess similar mouth-parts. The last become obtectate pupæ (p.
93), while the headless larvæ become pupæ within the larval skin.
Family: =Culicinæ= (_Gnats_).
Slenderly built, with long, thin legs. An elongated piercing proboscis
in the female. The male with feebly developed mouth-parts, and
feather-like antennæ. Both sexes suck up water and plant juices, and the
female blood as well; hence only the latter bites, especially at night.
They hybernate in the adult condition in cellars, barns, etc. The female
lays 250 to 300 eggs on any floating object in stagnant water (pools,
ditches, water-vessels). The larvæ (with large head, well-developed
prothorax, and a breathing-tube on the abdomen) live in water, as do the
pupæ. Several generations annually; especially in damp summers and
districts where the draining of the soil leaves much to be desired.
Although sand flies torment our domestic animals more than gnats, yet
these also may be very troublesome to them. They principally attack the
less hairy parts of the body (inner side of the ears, nose, mouth,
corners of the eye, arms, sexual parts). _Remedies_: Thorough draining
of the soil. Washing the domestic animals to be protected with a vinegar
extract of walnut leaves; rubbing with walnut leaves. Wherever possible,
any sores should be covered up, as they attract gnats, sand flies, and
flies; or the skin near them may be painted with turpentine or very
dilute carbolic acid. This is the less to be neglected, as several kinds
of flies eagerly lay their eggs in the sores of domestic animals.
Family: =Gallicolæ= (_Gall Gnats_).
[Illustration:
FIG. 110.—The Wheat Midge (_Cecidomyia tritici_), female.
]
Small gnats with large broad wings, much narrowed at the root, rounded
at the tip, and generally rough with hairs. Feelers made up of a large
number of spherical or cylindrical joints, covered with spreading hairs.
Proboscis short, legs long. The female has an ovipositor, with which she
inserts eggs in any part of a plant. At this particular spot a luxuriant
growth of vegetable tissue takes place later on, of varying extent, and
even forming a regular gall. The species of gall gnat are usually
brightly coloured, often red or yellow; these colours are lost, however,
in dried specimens. The larvæ are spindle-shaped, yellowish white,
yellow, or red; they become pupæ either in the soil or within the part
of the plant which they inhabit. Several species are destructive to
fruit-tree culture or forestry; I mention here only the most destructive
kinds which attack cultivated plants.
The =Hessian Fly= (_Cecidomyia destructor_).
[Illustration:
FIG. 111.—Plant of Barley, attacked by Hessian Fly. The pupæ at _a_.
]
Female about one-eighth of an inch long, male somewhat smaller. The
former velvety black, with black hairs, red belly, and red markings;
wings greyish; antennæ one-third the length of the body. Male black,
with reddish-yellow hairs, dirty red belly, and red markings. The name
“Hessian flies” was given in North America, during last century, because
it was believed they were introduced from Germany, in 1778, by Hessian
soldiers, in their straw. It is still very destructive in North America,
also in Germany, Russia, England, and Scotland. _Habits_: During April
or May, on warm still evenings, the female lays her eighty or ninety
eggs, singly or in pairs, on the lowest leaves of the still very short
haulms of rye, wheat, and barley. Eight days, on an average, after this
the maggots, which are at first oblong and spotted with reddish yellow,
are hatched, and glide down into the leaf-sheath, where they begin to
suck the haulm. They gradually alter their shape, becoming ovoid, and
transparent with the exception of the large yellowish white, quite
opaque fat body. They soon become pupæ (Fig. 111), which look like
grains of linseed, and are found in summer on the haulms of the ripe
grain. The presence of the constantly sucking larvæ causes great and
injurious distortions of the plant, especially obvious during the
flowering time, and for a short time afterwards. The haulm withers, and
shrivels at the point where the larvæ are present, _i.e._ above the
lowest node, or the lowest but one. At the time when the haulm begins to
turn yellow—that is, when the grain begins to ripen,—the larvæ become
pupæ; the haulm now easily breaks off at the infected spot; a strong
wind or heavy rain throws it to the ground. A badly infested field
looks, on this account, as if a herd of cattle had got loose and trodden
it all down, or as if the grain had been devastated by hail. Only a few
haulms bear ears containing normally developed grains. The flies emerge
from the pupæ in August and September, after which the females quickly
seek the winter corn, and lay their eggs singly or in pairs on the
leaves of the yet young plants. The larvæ creep between the leaf-sheath
and the still quite undeveloped haulm, and, in the case of small haulms,
a number of larvæ may collect together in the immediate neighbourhood of
the root, causing a spherical swelling. In many cases the plant dies if
its lower parts are inhabited by many larvæ. Before winter, the larvæ
attain their full size, leave the plants, and creep into the soil,
where, in the following spring, they become pupæ, from which flies
emerge fourteen days later. There are, therefore, two generations
annually. The _spreading_ of Hessian flies into regions where they were
formerly unknown may be caused by (_a_) straw containing the
linseed-like pupæ (straw for paper manufacture, packing, etc.); (_b_)
grain, among which are often found pupæ that have fallen out of the
haulms among the separated grain. _Remedies_: 1. Sowing the winter grain
as late as possible, so that the females of the summer generation when
they come out of the pupæ will find no winter-grain-plants in which to
lay their eggs. 2. Ploughing up the stubble immediately after harvest,
or else burning it, so that the pupæ found above the lower nodes are
either deeply buried or else burnt.
The =Scarlet Wheat Midge= (_Cecidomyia equestris_).
Female about ⅛ inch, male ¹⁄₁₂ inch; cherry red, with yellow hairs; back
of the thorax dark brown. Antennæ as long as the body in the male, half
as long in the female. On the wing from May till June; lays its eggs on
the leaves of grain-plants, at the base of the uppermost leaf by
preference. The blood-red maggots, when they are hatched, let themselves
slide down, and get between the leaf-sheath and haulm. Here they work
themselves into the haulm, making a longitudinal groove, the walls of
which swell more or less, and the end of which is indicated by an
obvious transverse thickening. The leaf-sheath hiding the attacked part
of the stem is usually more or less swollen. These gall-like outgrowths
take up a great deal of nutritious matter, not only from the affected
haulm but also from the plant at large, so that the regions not directly
attacked are retarded in their growth. The larvæ are full-grown at
harvest time, leave their hiding-places, and let themselves fall to the
ground, where the following spring they become pupæ, from which midges
quickly emerge. _Remedy_: After a year in which the insect has caused
great damage, the fields must be deeply ploughed in order to kill the
larvæ, which would otherwise live through the winter.
The =Wheat Midge= (_Cecidomyia tritici_).
[Illustration:
FIG. 112.—The Wheat Midge (_Cecidomyia tritici_): LI, larva in the
contracted, LII, the same in the extended condition. B, a wheat
flower: _a__{1} outer, _a__{2} inner glume, _b_, stamens; _c_,
brush-like stigmas; _d_, ovary; _l_, larvæ of the wheat midge. LI
and LII highly, B less highly, magnified.
]
Male ¹⁄₂₅ inch, female (Fig. 110) ¹⁄₁₇ inch, and possessing an
ovipositor which, when extended, is twice that length. Citron yellow,
slightly hairy; antennæ blackish, eyes black, legs dirty yellow. In
spring or early summer, the midges creep out of the soil in fields where
wheat has been planted the previous year. After pairing, the females
wander to fields where wheat or, more rarely, rye is growing. The
attacks of the midges commence when the ears begin to emerge from the
leaf-sheaths, and are continued throughout the flowering time of the
wheat. At night the female pierces the glumes with her ovipositor, and
lays three to ten perfectly transparent eggs in each flower. Each midge
lays eggs in several flowers, but two or more midges may use the same
flower for this purpose, so that as many as thirty maggots may be found
in one bloom (Fig. 112). The maggots, which are hatched out in a week,
creep down to the ovary and suck its juices. If many maggots live in one
flower it is sure to die, but if there are only a few it may produce a
grain, though this may be small. Ears infested by the maggots develop
yellow spots later on; many ears remain quite empty, and consequently
thin and upright. Full-grown maggot: ⅛ inch; straw yellow to chrome
yellow; quite transparent when very young. Is fully developed in three
weeks, and then lets itself fall to the ground (July or August). Becomes
a pupa the following spring; fourteen days later the midge escapes.
Family: =Rostratæ= (_Crane Flies_, _Daddy Longlegs_).
[Illustration:
FIG. 113.—The Daddy Longlegs, or Common Crane Fly (_Tipula oleracea_).
Left, the male and the maggot; right, the female and the pupa.
]
These very long-legged gnats live on the juices of plants, and do not
sting. The larvæ are legless, without a hard well-marked head; those of
most species live in mouldering plant parts (_e.g._ rotten wood), or the
decaying manures of our fields and meadows. A few species, however, are
very destructive, since they injure roots and other parts of cultivated
plants. The adult and larval stages of all the injurious kinds are not
yet distinguished. We know that the larvæ of the yellow and spotted
_Tipula maculosa_ are chiefly destructive in sandy soil; while more
binding clay soil and rich garden earth are infested by the larvæ of
_Tipula oleracea_ (Fig. 113), and damp meadows by those of _Tipula
paludosa_. The two last-named species are very much like one another;
grey or greyish brown with bright brown wings, having dark front margin.
Much is still unknown about the habits of “crane flies”; my researches
relate to the =Yellow-spotted Crane Fly= (_Tipula maculosa_). The adults
fly about in swarms during summer, usually from the beginning of June,
in the fields where the larvæ lived in spring. They lay their eggs
either in the same fields or (usually) in others, and are blown about
for long distances by the wind. Where the flies settle they lay each
time two or three black ovoid eggs, bent like a sickle, and repeat this
till all the eggs (200 to 250) are laid. Those fields which have
previously been grass land are the most infested by the crane flies. The
larvæ are headless, grey to lead coloured, with small prickles at the
hinder end of the body, and they first appear, in large numbers, under
the pieces of turf which are left behind in such fields, and which
appear to be the centres from which the destruction of the standing corn
begins. The larvæ are hatched out in summer, during the later part of
which, and during autumn, they devour plant roots; after hybernating,
they again attack the underground parts of plants the following spring.
They devour most readily the roots of grass and corn, but also those of
clover, rape, and several other plants, including some found in flower
and kitchen gardens. They are mainly injurious either in autumn or
spring, according to the nature of the plants attacked. Young
grain-plants are killed by them, older ones usually not. On fields where
winter corn grows they therefore do most damage in autumn, while this is
the case in spring on land where summer corn is cultivated. They are
sometimes harmless, since they can also feed on roots left behind in the
ground. The larva do not limit their ravages to underground parts; in
the evening, and also in the daytime during dark damp weather, they
devour parts of the first leaves of very young corn plants, though the
damage thus effected is often inconsiderable. In May the larva is ready
to pass into the pupa stage; it comes near the surface and becomes a
brown pupa, bearing small spines on the abdominal rings. After a rest of
fourteen to seventeen days, the pupa works its way upward till the front
part of its body sticks out of the soil. The fly then escapes.
_Enemies_: Mole, shrews, wagtails, grasshopper warbler, rook, gulls.
_Remedies_: When the maggots are very destructive in gardens they may be
collected, preferably in wet weather, since they then leave the soil
during the day. If they appear to an injurious extent on summer corn,
the fields should be rolled in April (either with the ordinary or the
spiked roller). At the time (June) when the crane flies swarm about the
fields and meadows in flocks, thousands of individuals can easily be
caught with a net.
Family: =Muscæformes= (_Gnat Flies_).
Gnats with relatively short legs, and antennæ which are in any case
shorter than the body, and are usually quite short and cylindrical,
possessing, however, six or more joints, while the antennæ of true flies
usually have only three joints. The gnat flies form, as it were, the
transition between the slender gnats with their long legs and antennæ,
and the more thick-set flies, the legs and antennæ of which are short.
Here belong the genera of =Shade Gnats= (_Sciara_, e.g. _Sciara Thomæ_,
the larvæ of which often wander about in companies, as the so-called
=Army Worm=), the =Sand Flies= (_Simulia_), and the =Hair Gnats=
(_Bibio_, _e.g._ the =Garden Hair Gnat=, _Bibio hortulanus_, the larva
of which gnaws the roots of plants, especially in humous garden soil).
The =Sand Flies=, or =Mosquitoes= (_Simulia_),
have thick-set bodies, short legs, and short nine or ten-jointed
antennæ; they are from ¹⁄₂₅ to ⅕ of an inch long, and have a short but
sharp proboscis, with which they suck up the flower juices which
constitute their chief food. But the female also sucks the blood of
human beings and animals, making herself exceedingly annoying in this
way. Its larval state is passed through in stagnant water; its
appearance is therefore local, and is especially favoured by damp
summers. The mature sand flies are found from early spring or through
the whole summer; several generations succeed one another in the same
year. Sand flies often appear in swarms, containing thousands of
individuals. Since the female eagerly creeps into the ears, noses, and
corners of the eyes in horses and oxen, she is extremely annoying and
even dangerous. Her bite produces a smarting sensation, and may cause
actual boils to form in the skin. When a large swarm of sand flies
settles on a herd of cattle or on some horses, these animals become
maddened and furious; they often rush wildly round for so long that they
fall down dead. _Simulia reptans_ is a common British form. _Remedies_:
Compare what is said on p. 165, about gnats. Sand flies can usually be
kept from horses’ ears by means of ear-caps.
Family: =Tabanidæ= (_Gad Flies_).
[Illustration:
FIG. 114.—The Rain Breeze Fly (_Hæmatopota pluvialis_).
]
Large or medium-sized flies with thick-set body, large broad head, flat
abdomen, and strong legs. The proboscis is less developed in the male,
which lives merely on plant juices, than in the blood-sucking female.
The cylindrical whitish larvæ live in earth, and are harmless. But the
female insects bite human beings, and the larger kind attack horses and
cattle in such a manner that blood-drops may be seen on the ground under
the animals attacked, if these remain for a time in the same spot. There
belong to this family: 1. The =Breeze Flies= (_Tabanus_), large insects
up to ⅘ inch long, which are seen flying about with a buzzing sound over
meadows and fields in the sunshine (=Ox Fly= = _T. bovinus_; =Horse Fly=
= _T. autumnalis_). 2. The =Lesser Breeze Flies= (_Hæmatopota_), smaller
and more slender, with grey wings, bite most before a storm and in hot
sultry days. 3. The =Blinding Breeze Flies= (_Chrysops_), as large as
the Lesser Breeze Flies, but broader, with shining golden-green eyes and
wings marked with black. _Remedies_: Compare p. 165, and above; draining
the soil, however, is no good here.
Family: =Muscidæ= (_True Flies_).
These are flies with three-jointed antennæ, constructed on the type seen
in the common house fly. Here are included the =Caterpillar Flies=
(_Tachina_), the =Flesh Flies= (_Sarcophaga_), =Common Flies= (_Musca_),
=Flower Flies= (_Anthomyia_), =Green-eyed Flies= (_Chlorops_), etc.
The =Caterpillar Flies= (_Tachina_)
are black, grey, or reddish yellow flies, reminding one by their
appearance of the common house fly or the blue-bottle. They play the
same part in the economy of nature as the sand wasps (p. 129), but
always lay their eggs externally on the skin of the host; the maggots
consequently never prey on those insect larvæ which live in the tissues
of plants or in the soil.
[Illustration:
FIG. 115.—Caterpillar Fly (_Tachina fera_).
]
The =Flesh Flies= (_Sarcophaga_)
have a longish abdomen, with large bristles on the hinder margins of the
segments. Thorax with three longitudinal streaks. The flies suck up
sweat, but do not bite. The eggs develop within the abdomen of the
mother; the flies lay the young larvæ in dead flesh; also, if not kept
clean, in wounds of human beings and animals,—sometimes, too, in the
genital opening of horses, cattle, and swine, in which case the maggots
live as true parasites in the vagina and uterus, causing a secretion of
mucus, upon which they live. Two to three generations yearly; fifty to
eighty maggots each time. _Remedies_: On keeping the flies from cattle,
cf. p. 165; to keep them from meat, flynets, a gauze cover. =Blow Fly=
(_S. carnaria_), with black speckled abdomen.
The =Common Flies= (_Musca_)
are coloured dark or shining green. The headless white maggots live in
dung (=House Fly= = _Musca domestica_), in fresh or decaying meat
(=Blue-bottle= = _M. vomitoria_), exceptionally (_M. vomitoria_) in
wounds that are not kept clean, or in the vagina of several domestic
animals. _Remedy_: Compare above (“Flesh Fly”).
The =Flower Flies= (_Anthomyia_).
These are found on flowers, and resemble many common flies in appearance
and colour. The headless white maggots live in dung, also in decaying or
sound parts of plants; a few species may sometimes develop in the one
kind of material, sometimes in the other. _Anthomyia meteorica_ swarms
round the heads of domestic animals, and may even cause inflammation of
the eyes and ears. The =Wheat Bulb Fly= (_Anthomyia coarctata_, about a
quarter of an inch long, yellowish grey, with black hairs) lives as a
larva during winter and spring in the hearts of rye and wheat plants,
the leaves of which become yellow in consequence. During April and the
beginning of May the larvæ quit these plants and become pupæ in the
ground. The second generation can, in like manner, live in various kinds
of summer grain. The =Lupine Fly= (_A. funesta_)—nearly one-fifth of an
inch long, brownish grey (male) or whitish grey (female), with black
legs—digs, when a larva, tunnels in the roots, stems, and seed-leaves of
young lupine plants, causing the root and stem to turn black, and the
seed-leaves to wither. _Preventive Measure_: Early sowing of the
lupines. The =Mangold and Beet Fly= (_A. betæ_), a quarter of an inch
long, yellowish grey, lays its eggs, five to eight in number, in the
young leaves of mangold and beet. The maggots devour the green substance
of the leaf between the two layers of epidermis, so that the leaves die.
In June the maggots creep out of the leaves, and become pupæ in the
soil. The flies quickly escape, and two or three generations follow one
another in the year. As, however, the leaves are now larger, the later
generations only effect a small amount of damage. _Preventive Measure_:
Close sowing of the turnips, so that even if many are killed there will
still be enough young plants. The =Cabbage Root-eating Fly= (_A.
radicum_) and the =Radish Fly= (_A. floralis_) live as fleshy, wrinkled,
dirty white maggots with black dots, in the underground parts of turnip,
cabbage, horseradish, radishes, etc. They lead a similar life to the
=Cabbage Fly= (_A. brassicæ_), the cylindrical, smooth, yellowish white
maggot of which lives in the underground parts of cabbage, turnip, and
rape. The roots attacked swell here and there (Fig. 116), and later on
decay; the leaves of the infested plants first become of a dull leaden
colour and then wither. Entire fields of cabbage, rape, or turnips, are
often destroyed by cabbage fly maggots. The insect passes the winter in
the pupa state; the flies appear early in the spring, and usually twice
more later on. It is therefore most desirable to pull up and burn the
infested plants as soon as possible. A proper rotation of crops should
also be practised. [The =Onion Fly= (_A. ceparum_) maggot feeds within
the bulbs of stored onions. The male fly is grey, the female yellow.]
[Illustration:
FIG. 116.—A turnip infested by the Cabbage Fly: A, swellings; G,
tunnels.
]
The =Cheese Fly= (_Piophila casei_),
one-fifth of an inch long, slender, with a metallic sheen, almost
hairless, black, with dirty yellow legs and wings of glassy clearness.
These small flies abound in front of the windows of places where cheese
is stored; in summer and autumn the shining white maggots, which are
cylindrical in form with tapering ends, and one-third of an inch long,
live in large numbers in old cheese, gnawing it through and through, and
making it dirty. Now and then they spring forwards by bending their
bodies into a circle and suddenly straightening them again. They become
pupæ on the walls or in straw, near the cheeses from which they have
crept out. _Remedies_: Keeping the cheeses clean; mechanical exclusion
(gauze screens outside the windows, enclosure in chests).
The =Green-eyed Flies= (_Chlorops_)
include a number of small flies, under one-sixth of an inch long, with
spherical head, rounded greenish eyes, strongly arched thorax, and short
egg-shaped abdomen, pointed in the male and blunt in the female. The
headless larvæ live in the haulms of grasses and species of grain; the
life history of a few forms only is adequately known. A few are harmful,
especially as there are two or three generations annually. The late
summer generation often appears in large numbers, indeed in actual
swarms. Since no species lives exclusively on corn, it is impossible to
keep them down for a long period of time. I describe only two species:—
[Illustration:
FIG. 117.—The Ribbon-footed Corn Fly (_Chlorops tæniopus_).
]
The =Ribbon-footed Corn Fly= or =Yellow Haulm Fly= (_Chlorops
tæniopus_), nearly one-sixth of an inch long, shining yellow; the
antennæ are black, and there are three longitudinal stripes on the
dorsal side of the thorax and four transverse bands on the abdomen of
the same colour; the latter region is scarcely longer than the thorax.
The insect (Fig. 117) is on the wing in cornfields about the middle of
May. It lays its eggs separately on the upper leaves of various species
of wheat, rye, and barley, choosing the upper side of the blade, not far
from the sheath. Only those plants are selected for the purpose in which
the ears are still hidden deep down between the leaf-sheaths. Wheat
plants are picked out whenever possible. The maggot when hatched works
its way between leaf-sheath and haulm, digging into the latter. It is
yellowish white, clear and translucent, and about a quarter of an inch
long. While still young it penetrates the haulm, and then attacks the
developing ear or the upper part of the haulm which immediately adjoins
this, and travels gradually up to the first node of the haulm or nearly
so, always continuing to slowly suck. Thus a furrow, from 2½ to 3½
inches long (Fig. 118, C and D), is formed along the surface of the
upper part of the haulm, and often also along the lower part of the ear.
The part of the haulm attacked swells transversely, and the part below
often remains short, so that the ear cannot emerge from the leaf-sheath;
but, in any case, only small worthless grains are developed. The furrow
is always much deeper below than above, and its margins thicken in
consequence of the swelling of the tissues of the haulm. At the end of
June or in July, the larva becomes a pupa at the lower end of the
furrow. The yellowish-brown pupa (Fig. 118, B), one-fifth of an inch
long, remains as such in the furrow for three weeks; the fly emerges in
August. Very considerable damage may be done by the first generation, of
which the habits have just been described. During 1869 in Silesia, from
two-thirds to five-sixths of the ears in many fields remained hidden in
the leaf-sheaths, and consequently gave no increase. The first
generation of the ribbon-footed corn fly can also develop in the way
described in the haulms of several grasses, _e.g._ in species of _Poa_
and _Holcus_.
The flies, emerging in late summer, lay their eggs, here, too,
separately, on the leaves of grass or corn. Wherever possible, they seek
out for the purpose the winter wheat plants then present in the fields,
but also content themselves with rye, or even with wild or meadow
grasses; they have to be satisfied with grasses if, at the time of
egg-laying, the winter corn is not yet up. The maggot, when hatched,
works its way to the inner side of the leaf-sheath, and thence to the
apex of the still very small haulm; there it remains during the winter.
The damage becomes apparent the following spring. The growth in length
of the haulm in question is extremely small, while growth in thickness
increases to an abnormal extent. Almost all the leaves completely
surround the haulm, which swells to an enormous extent (Fig. 119),
together with the enclosing leaf-sheaths, which are much broader than
usual. The unattacked plants are naturally much larger than the sickly
ones, and deprive these of air and light, so that they die down, being
overshadowed, not only by the sound haulms, but also by their own
secondary shoots. The resulting damage may be tolerably great,
especially at the edges of the field. It may happen that both summer and
winter generations of the ribbon-footed corn fly are harmful in the same
district; but it frequently happens that only one or the other is
complained of in a particular spot. It is only natural that the flies,
which swarm around in May, and again in August, September, or October,
should not always find suitable corn plants upon which to deposit their
eggs. In such cases grasses are used. _Remedies_: Sowing the summer corn
as early as possible, that it may be developed to a stage which is
unsuitable for the purpose of egg-laying, before the flies appear. The
winter seed, however, must be sown as late as possible, so that the
second generation of flies may find no corn plants fit to lay their eggs
upon. Bearded wheat, especially the strongest varieties, should be sown
in preference to awnless wheat. Careful tillage and suitable manuring,
so that strong plants of rapid growth may be produced.
[Illustration:
FIG. 118.—The Ribbon-footed Corn Fly (_Chlorops tæniopus_); larva (A)
and pupa (B) magnified. To the left a wheat haulm and ear (C) with
the furrow (_q_) dug out by the larva; the pupa (_p_) is seen at the
bottom of the furrow. To the right a wheat haulm with furrow (D) and
the larva (_r_) lying in it.
]
[Illustration:
FIG. 119.—A wheat plant distorted by
the winter generation of the Ribbon-footed
Corn Fly.
]
The =Frit Fly= (_Chlorops_, or _Oscinis frit_)
(Fig. 120, C) is about one-tenth of an inch long, shining black, with a
metallic sheen. Legs short, feet yellow. Maggot (Fig. 120, A) yellowish
white, about one-eighth of an inch long, cylindrical, and tapering in
front. Usually three generations. 1. The maggots of the first generation
are found during May, in the lower part of the haulm of summer corn
(especially oats and barley); the plants attacked either die off
entirely, or some haulms develop further, remaining small, however, and
yielding only a few light grains. The base of the haulm thickens
abnormally, but the growth in length is always small; the leaves, too,
grow badly, first becoming yellowish at the tip, and then entirely
yellow or reddish. The symptoms of disease are exhibited to a less or
greater extent, according as few or many (even up to ten) maggots
inhabit the base of a plant. The shining brown pupæ (Fig. 120, B) are
found in the lower part of the haulm, or between the leaf-sheath and the
haulm (Fig. 120, D). The adult insect is on the wing at the end of May
and in June. The first generation often appear on wild or meadow
grasses, and are chiefly seen on summer corn when this is sown late or
develops slowly. 2. The maggots of the second generation are found in
average cases during July, on the as yet scarcely ripe grains of late
summer corn, principally those of oats and barley, often occurring also
in the haulms of grasses. They keep between the awns, and suck the
juices of the soft developing grains, which are rendered incapable of
growth, and in any case remain light. The maggots of the second
generation develop more quickly than those of the first or third; they
are mature in three weeks. The pupa rest is very short, and the flies
appear in August, September, or October. They lay their eggs on the
leaves of winter corn or winter grasses, and from these eggs are
developed (3) the maggots of the third generation, which are to be
found, during September and October, in the heart of winter corn and
grasses, injuring these plants in exactly the same way that the maggots
of the first generation injure the summer corn. The insect passes the
winter as a pupa in winter corn plants or grasses. It is but very rarely
that all _three_ generations infest the corn of any particular region;
as a rule, only the first, second, or third generations do this, or the
first _and_ third; in such cases the other generations live on grasses.
_Remedies_: Extermination of the insect is impossible, since it can
always go from corn to grass plants. Oats and barley are almost always
attacked in spring, if in the immediate neighbourhood there is winter
rye inhabited by the maggots, for the flies, when they emerge the next
spring, seek out the summer corn. This may, however, be made impossible,
or at least difficult, if a field of peas, clover, lupines, rape, or
some other crop not of gramineous nature, is interposed between fields
of winter corn and those of oats, barley, or similar late sown crops of
summer corn. Sowing the summer corn (especially oats and barley) as
early as possible.
[Illustration:
FIG. 120.—The Frit Fly (_Oscinis frit_, L.): A, larva; B, pupa; C,
fly; D, a diseased corn plant, as appearing in spring,—the larvæ and
pupæ are seen of the natural size in the lower part of the plant.
]
Family: =Syrphidæ= (_Hover_ or _Hawk Flies_).
Chiefly includes brightly coloured flies, marked with yellow or red and
black bands or patches (Fig. 67), and flying rapidly with a buzzing
noise. They can remain suspended at the same point in the air by moving
their wings up and down with great rapidity. A few of them resemble the
humblebee in their thick covering of hair; others, with yellow and black
abdomen, look like wasps (_Syrphus_). The proboscis is adapted for
sucking, but not for piercing; these flies suck their food from flowers.
They are fond of hovering in the air in sunny places. The legless larvæ
vary, according to species, in their habits, and consequently in their
structure. Some (those of the =Drone Flies=, _Eristalis_) live in
stagnant water; others (_e.g._ those of _Eumerus lunulatus_) live in
onions, which they hollow out; while some, again, develop in rotten
wood, etc. The maggots of the =Aphis-eating Flies= (_Syrphus_), however,
feed on insects, chiefly aphides, which they suck out completely. They
are elongated, tapering in front, thickened behind, move like leeches,
and vary much in colour (green, yellow, brown, chequered), according to
the species. As they grow quickly, and consequently more than one
generation is found each year, and as they are very voracious, we must
look upon them as powerful allies for the extermination of aphides.
Family: =Stomoxydæ= (_Stable Flies_).
In many points the stable flies resemble ordinary flies, but their
mouths are adapted for piercing. Their painful bites make them known to
every one as pests to human beings and cattle. Here belongs the common
=Stable Fly= (_Stomoxys calcitrans_), a form often confounded with the
house fly, but distinguished from it by a sharp proboscis projecting at
right angles, besides which the abdomen is more of a yellowish grey. The
maggots usually live in dung. Two generations yearly: the first flies
about in March; the second, and much more numerous one, in August and
September. _Remedies_: Cp. p. 165.
Family: =Œstridæ= (_Bot Flies_).
Medium-sized or large flies (Fig. 121), with thick hemispherical heads,
and mouth-parts not strongly developed. The antennæ can be drawn back
into deep pits. The hot flies make a buzzing sound during flight. The
headless, twelve-ringed maggots live in the bodies of various mammals.
Their skin is provided with numerous wart-like projections, or circlets
of spines. When very young the maggots are elongated and cylindrical,
and then possess a mouth-hook, which disappears during the later moults.
As soon as the maggots are fully developed they leave the body of the
animal they inhabit, and let themselves fall to the ground, where they
become pupæ within the shrivelled larval skin.
The following genera are distinguished: =Warble Flies= (_Hypoderma_),
and =Bot Flies= (_Œstrus_ and _Gastrus_, or _Gastrophilus_). To the
first-named genus belongs the
=Ox Warble-fly=, or =Ox Bot Fly= (_Hypoderma bovis_),
two-fifths of an inch long, black. Hair: whitish yellow on the head;
reddish yellow on the fore part of the thorax, black on the hinder part;
grey on the fore part of the abdomen, black in the middle, and reddish
yellow behind. Legs black. Wings brownish, not quite transparent.
On the wing during summer (June to September). As soon as the cattle
hear the flies buzzing around (especially on hot days) they become very
restless, run about as if mad, and even plunge down steep places. Young
cattle are selected for egg-laying; the elongated white eggs are fixed
separately to hairs. The maggot, elongated when first hatched,
perforates the skin, and gets into the subcutaneous connective tissue,
where it does not, as a rule, keep to any one place, but wanders here
and there, sometimes penetrating the flesh, or even entering the spinal
canal. It always, however, wanders back again later on into the
subcutaneous connective tissue, where it gives rise, during the winter
or the following spring, to one of the well-known tumours, or “warbles.”
After fixing on a definite spot, it moults, becoming broader, and of a
yellowish white colour. The maggot first causes an increased flow of
blood to the part, and then inflammation. An excavation filled with
matter is thus developed, and there is gradually formed a connective
tissue sac communicating with the exterior by a minute tube. In spring,
or early summer, the warble, which is visible externally, has reached
the size of a pigeon’s egg; the maggot meanwhile becomes first greyish
yellow, then brown patches appear, and lastly it assumes a dark brown
colour, is an inch long or rather more, and somewhat swollen. It is now
ready to pass into the resting stage, crawls out, and lets itself fall
to the ground, where, within the larval skin, it becomes a black pupa
four-fifths of an inch long, from which, about four weeks later, the fly
creeps out. _Damage done_: If the warbles occur only in small numbers on
an animal, its health is not much affected, though this must undoubtedly
be the case if there are many, say fifty, or even up to a hundred, in
the same animal. In such cases the yield of milk will be considerably
diminished. Holes, too, are present in the skin, which, though they may
close again, if the animal remains alive, always leave a thin place. The
outer surface of meat from animals infested with warbles is dirty
yellow, flaccid, or even soft and jelly-like (“licked beef”); it must be
scraped off. _Enemies_: Starlings settle, in spring, on the backs of
infested cattle, and seize the parasites with their beaks. Starlings,
rooks, and wagtails destroy the maggots ready to become pupæ, as they
lie on the ground. _Remedies_: Washing the back, shoulders, and loins
with vinegar extract of walnut leaves during the summer, to keep away
the bot flies. In spring: squeezing out the maggots from the warbles,
having previously opened them, when necessary, with a penknife. If the
warble is “ripe,” _i.e._ if it has opened so far that the black hinder
end of the maggot can be seen, the opening may be stopped with fat or
cart-grease, by which the larva will be killed where it lies.
The =Sheep Bot Fly= (_Œstrus ovis_),
two-fifths to three-quarters of an inch long, yellowish grey, almost
hairless; head large, round, reddish; thorax grey, with small black
warts; abdomen yellowish white; legs short, bright; wings of a glassy
clearness. The flies are found (in September) on the walls of
sheepfolds, and in woods near which sheep graze. On sunny days the
female flies round the sheep, in order to deposit her brood upon them.
The sheep threatened press their nostrils to the ground, though this is
not of much use. The maggots are hatched while still in the body of
their mother, and are deposited by her on the margins of the nostrils.
These little maggots creep about on the mucous membrane lining the
internal cavities of the nose, causing intolerable itching. The sheep
try to get rid of the intruders by shaking their heads and rubbing their
noses on the ground. The maggots, however, creep further into the nasal
cavities, and get into the hollows of the frontal bone and upper jaw,
perhaps even into the horns. In these places they feed on the fluid
which their presence causes the mucous membrane to give out in large
quantities. The maggots remain as such for nine months, during which
time they alter their shape in various ways. Those just born are white,
one-twenty-fifth of an inch long, while those which have reached the
length of two-fifths of an inch are yellowish white. Individuals ready
to become pupæ are about an inch long, yellowish brown, with dark
transverse lines; they wander back to the nasal cavities and thence to
the exterior, often being expelled by sneezing. In the soil they become
pupæ, first of a brown, then of a black colour, within the larval skin;
the flies emerge in six or seven weeks. Different maggots develop at
different rates, according to the nature of the cavities into which they
penetrate.
The maggots cause the disease known as “false gid,” which appears most
obviously from March to May; at this time the parasites are tolerably
well developed. They irritate the mucous membrane of the cavities of the
head in which they live, causing an unusually large flow of blood to
these parts, as a result of which the mucus secreted in the nose
increases largely in quantity (sneezing, snuffling), and the brain
begins to work abnormally (uneasy movements of the head, high lifting of
the feet; in worse cases, rolling of the eyes, gnashing of the teeth,
and foaming at the mouth). The sheep have also an intolerable itching of
the nose, which they rub in consequence on the ground, against posts, or
their own legs; besides this, there may be inflammation of the eyelids
and increased secretion of tears. They are also apt to grow very thin.
The disease is more frequent, and the symptoms severer, in young than in
old sheep. False gid may cause death; the animal is cured, however,
after the maggots have crept out. _Preventive Measures_: Keeping the
sheep away from the edges of woods, avenues, etc., where the flies live
by preference. When sheep are killed, the maggots coming from the head
should be collected and destroyed. Smearing the margins of the nostrils
with tar, or rubbing them with walnut leaves, before the sheep go to
pasture in the morning. For sheep, which in late summer rub their noses
up and down tree stems, walls, hedges, or their own legs, substances
that cause sneezing may be employed, _e.g._ cheap snuff, which is best
introduced into the nose by means of a quill-feather. Later on, when the
maggots have passed from the nasal cavities into the frontal sinuses,
etc., sneezing does no good. Operations seldom succeed in removing all
the maggots.
[Illustration:
FIG. 121.—Horse Bot Fly (_Gastrus equi_): _a_, egg on a hair, strongly
magnified; _c_, younger (magnified), and _b_, older larva; _d_,
opened pupa case; _e_, fly.
]
The =Bot Flies= (_Gastrus_, or _Gastrophilus_) live in various parts of
the stomach (in left side of horse’s stomach) and intestine. I give,
first of all, a compressed tabular view of the external characters and
mode of life of the four British species. (See next page.)
_Diseases caused by Bot Flies._—The maggots bore into the walls of the
stomach and intestines until they reach the layer in which the
blood-vessels, lacteals, and lymphatics ramify; they then suck the
juices found in these vessels, and also serous fluids. In small numbers
they are often almost harmless, but when a great many are present they
hinder the secretion of the digestive juices. They may also set up
inflammation of the intestinal coats, or may cause death by internal
bleeding if they perforate the wall of an artery. In foals they often
bore right through the wall of the intestine, and enter the abdominal
cavity, where they may set up inflammation of the peritoneum or of the
mesentery. There may be as many as a hundred or two hundred maggots in
the stomach or intestine, and they then cause, at the very least,
digestive disturbances and colic. If the maggots (_G. nasalis_) get into
the windpipe (or larynx) they interfere with the breathing; if into the
gullet, with swallowing. In either case death may ensue (winter, early
spring). _Remedies_: Killing the flies as they lay their eggs. Removing
the eggs by brushing, combing, and washing; the last is best done with
warm water, to which some caustic potash is added. Rubbing the lips and
nostrils, neck, chest, and fore legs with walnut leaves, or a decoction
of the same.
────────────────────┬──────────────────┬──────────────────┬──────────────────
SPECIES. │ FLY. │ EGG. │ MAGGOT.
────────────────────┼──────────────────┼──────────────────┼──────────────────
=Horse Bot= │½ to ⅖ inch, very │White: on the │At first flesh
(_Gastrus equi_). │ hairy, like a │ hairs of the │ red, then
│ humblebee; │ mane, neck, │ yellowish-brown.
│ brownish yellow.│ chest, fore │ Lives in the
│ Fore part of │ legs, and hind │ stomach of the
│ thorax with │ feet of horse. │ horse, often in
│ yellowish-brown,│ │ large numbers.
│ hind half with │ │
│ black hairs. │ │
│ Abdomen with │ │
│ brown hair in │ │
│ front, │ │
│ brownish-yellow │ │
│ behind. │ │
=Cattle Bot= │Male about ½ inch,│Black: on the same│First yellowish
(_Gastrus_ │ brown, closely │ parts of the │ grey, then
_pecorum_.) │ covered with a │ horse’s body as │ blood-red. First
│ mixture of │ in the preceding│ in the small
│ yellowish and │ species; │ intestine, and,
│ black hairs. │ exceptionally on│ for some time
│ Wings │ the hairs of │ during June or
│ smoke-coloured. │ horned stock. │ July, in the
│ Female rather │ │ rectum of the
│ larger. Head, │ │ horse. When
│ thorax, and │ │ ready to become
│ first segment of│ │ pupæ, they creep
│ the abdomen with│ │ out of the anus,
│ colour and hairs│ │ to the margin of
│ as in the male; │ │ which, however,
│ rest of abdomen │ │ they may remain
│ black, and │ │ sticking for
│ tapering │ │ some time.
│ posteriorly. │ │
│ Wings │ │
│ smoke-coloured. │ │
=Red-tailed= =Bot= │About ⅖ inch. Fore│Black: on the lips│First red, then
(_Gastrus_ │ part of thorax │ and margins of │ bluish-green. To
_hæmorrhoidalis_).│ dark fawn │ the nostrils in │ begin with, in
│ colour, with │ the horse. │ the cavities of
│ bright yellow │ │ the nose or
│ fur-like hair; │ │ mouth, in the
│ hinder part │ │ horse, very soon
│ black. Abdomen │ │ in the stomach
│ shining black, │ │ or small
│ with yellowish │ │ intestine,
│ white hair in │ │ remaining there
│ front, black in │ │ several months;
│ the middle, and │ │ then, a few
│ orange yellow at│ │ months longer,
│ the tip. Wings │ │ in the rectum.
│ of glassy │ │ Exceptionally,
│ clearness, with │ │ the maggots
│ dark brown │ │ remain in the
│ veins. │ │ gullet for some
│ │ │ time.
=Nose Bot= │Nearly ½ inch (not│White: on the lips│Yellowish white.
(_Gastrus_ │ including the │ and margins of │ In the first
_nasalus_). │ long ovipositor │ the nostrils in │ part of the
│ of the female). │ the horse. │ horse’s small
│ A fine but close│ │ intestine, near
│ covering of │ │ the aperture of
│ hairs; │ │ the stomach;
│ variegated, not │ │ exceptionally in
│ always evenly │ │ the nasal
│ covered with │ │ cavities,
│ hair, especially│ │ gullet, and
│ not on the black│ │ stomach.
│ abdomen (partly │ │
│ white, black, │ │
│ orange yellow, │ │
│ yellowish grey);│ │
│ thorax a shining│ │
│ blackish brown, │ │
│ covered with │ │
│ fine, golden │ │
│ yellow hair. │ │
│ Wings clear as │ │
│ glass, widely │ │
│ spread when at │ │
│ rest. │ │
────────────────────┴──────────────────┴──────────────────┴──────────────────
Family: =Pupipara= (_Louse Flies_).
Body flat and broad; skin leathery and tough. Fore legs curved, adapted
for climbing among the hairs. Some (_e.g._ the Forest Fly) have a pair
of wings, others (the Sheep Louse Fly) are wingless. They bring forth
living maggots, each time one only, which is ready to become a pupa
immediately. They reproduce several times. Here belong: 1. The =Forest
Fly=, =Spider Fly=, or =Flat Fly= (_Hippobosca equina_), about one-third
of an inch long, brown, with broad abdomen, and two broad stumpy wings.
Occurs in summer and early autumn, chiefly on horses, especially near
the anus, on the belly, and on the flanks. It sucks blood, and irritates
by running about on the body. Seldom flies. 2. The =Sheep Louse Fly=,
wrongly called “sheep louse” and “sheep tick” (_Melophagus ovinus_);
about one-fifth of an inch long, wingless, rusty yellow, with brown
abdomen, very hairy. Climb slowly about among the wool of the sheep, and
suck blood. Their excrement may colour the wool green. Lambs especially
are much hindered in their growth by this fly. The fleece is also
damaged, for the itching set up by the insect forces the animal to rub
itself against things so that the wool gets pulled out. The flies are
chiefly found on meadow sheep; but relatively few in winter. The
parasites leave the body of their host for the purpose of reproduction,
and lay their maggots, which at the time of birth are nearly one-sixth
of an inch long, under little bits of earth or heaps of dung. When sheep
are kept in folds no permanent result can consequently be expected from
the use of any remedy if, at the same time, the fold and all its
contents are not kept clean. The walls must be cleansed, and washed with
caustic potash, to which carbolic acid has been added. _Curative
Washes_: A decoction of walnut leaves and vinegar. Turpentine, soapsuds,
decoction of tobacco. Washes containing arsenious acid (_e.g._ Bigg’s
Improved Sheep and Lamb Dipping Composition) must be used with caution;
unpalatable substances may be added, so that the sheep will not lick
them, or else a muzzle may be employed.
NINTH ORDER: =Aphaniptera= (FLEAS).
Body strongly compressed laterally. Head small. Mouth-parts adapted for
sucking and biting. Legs long, especially the last pair. They possess
the power of springing. Wingless. Complete metamorphosis. Larva
worm-like, legless, hard-headed. The =Dog Flea= (_Pulex serraticeps_),
which only occasionally passes on to human beings, lives on dogs and
cats. _Remedy_: Sprinkling the moistened hair with Persian insect powder
or powdered parsley seed.
TENTH ORDER: =Parasita= (LICE).
Body flattened. Legs adapted for climbing among hairs and feathers, as
the last joint of the foot is hook-shaped, and can be bent back against
the preceding joint; a hair can thus be held fast between the two
joints. Eyes absent or ill developed (simple). Wingless. The eggs
(“nits”) are fastened by the mother louse to the hairs of the host; the
young lice resemble the old ones in almost all particulars; there is no
true metamorphosis. All lice have a kind of proboscis, which can be
protruded and retracted, and upon which are placed the mouth-parts,
which enable it to be used for sucking or biting. According to the last
feature a distinction can be drawn between true or blood-sucking lice
and biting lice or fur-eaters, which devour small scales derived from
the skin or else bits of hair and feathers. Lice multiply very rapidly
on the bodies of human beings and animals when insufficiently cleansed,
and under these circumstances more on sick and ill-nourished individuals
than on those which are healthy and well nourished. It is obvious that
the true, blood-sucking lice usually injure their host more than the
biting lice, which, however, especially when present in large numbers,
may cause an intolerable and injurious itching by their movements here
and there. _Preventive Measures_: Suitable feeding and treatment. Proper
care of the skin. _Remedies_: Repeated combing with a comb which has
been dipped into a solution of soda. Rubbing the badly infested spots
with soft soap and soda, washing them out after twenty-four hours. Among
other washes are—6 parts soft soap, 1 part benzine, 10 to 15 parts
water; or tobacco water, 1 part of common tobacco in 20 to 25 parts
water; arsenious acid, in various mixtures, _e.g._ in Bigg’s Composition
(p. 193). Employ the muzzle.
[Illustration:
FIG. 122.—Horse Louse (_Hæmatopinus macrocephalus_), magnified ten
times.
]
CLASS II.: =MYRIOPODA= (CENTIPEDES AND MILLIPEDES).
Respiration by tracheæ, as in insects. The body consists of a head and a
large number of very similar segments, each of which possesses limbs.
One pair of antennæ.
This class is divided into two orders: (1) that of =Centipedes=
(_Chilopoda_), with mouth-parts adapted for seizing prey, and _one_ pair
of legs to each segment; (2) that of =Millipedes= (_Chilognatha_),
adapted for devouring substances resembling humus, also the parts of
plants; and _two_ pairs of legs to each segment. Here belong, above all,
the =Snake Millipedes= (_Julus_) or “False Wireworms” (Fig. 123), of
which several species eat out germinating seeds (peas, beans, mangolds,
and beet), and also attack juicy plant parts (potatoes, turnips,
carrots). Seedlings may be protected by using potatoes to draw away the
millipedes.
[Illustration:
FIG. 123.—Common Snake Millipede (_Julus terrestris_), somewhat
magnified.
]
CLASS III.: =ARACHNOIDEA= (SCORPIONS, SPIDERS, MITES).
Air-breathing (by ordinary or modified tracheæ); the lower forms breathe
with the skin. Body at most consists of two chief regions, since head
and thorax are always fused together, making up a cephalothorax (Fig.
124); but this may again be united with the always unsegmented abdomen
into a single piece (Fig. 127). The last is the case with the mites, in
which, therefore, the characters of segmented animals can only be
recognized in the limbs. In the true spiders (Fig. 124) the body
consists of cephalothorax and abdomen. Arachnids have always four pairs
of legs, which, in the true spiders, are attached to the cephalothorax,
in the mites to the front part of the unsegmented body.
[Illustration:
FIG. 124.—A Spider (_Salticus scenicus_).
]
The chief Orders belonging here are: (1) true =Spiders= (_Araneida_);
(2) =Scorpions= (_Scorpionida_); (3) =Harvestmen= (_Opilionida_); (4)
=Mites= (_Acaridea_). Only the last contains species of importance
agriculturally.
ORDER: Acaridea (MITES).
Small arachnids, in which the cephalothorax and abdomen are fused
together into one piece (Fig. 127). The just-hatched young have three
pairs of legs, the adults, of course, four.
Family: =Acaridæ= (_True Mites_).
Soft skin. No tracheæ, no eyes. Legs short, often with a sucker at the
end. Here belong the =Cheese Mite= (_Acarus siro_), the =Meal Mite=
(_Tyroglyphus farinæ_), and several other species living in dead organic
substances; also—
The =Itch=, or =Mange Mites=.
These live as parasites on or in the epidermis, and cause the _itch_ or
_mange_ (scabies) in man, as well as in several domestic animals. By
means of the structure and habits three genera are distinguished:—
1. Digging, blood-sucking mange-mites living in the skin (_Sarcoptes_);
2. Blood-sucking mange-mites living on the outer surface
(_Dermatocoptes_);
3. Mange-mites which merely devour scales of the epidermis
(_Dermatophagus_).
[Illustration:
FIG. 125.—Mange Mite of the Pig (_Sarcoptes scabiei_, var. _suis_),
seen from the ventral side.
]
It is obvious that sarcoptic scabies is not so easily cured in the same
host as the dermatocoptic scabies, since the mites causing the former
dig their passages into the epidermis, while those causing the latter at
least remain on the surface. Dermatophagic scabies is most easily got
rid of, since the mites which cause it not only remain on the outer
surface of the skin, but also, instead of holding fast, run about here
and there; it is easily understood that this kind of mange can often be
removed by simple brushing.
[Illustration:
FIG. 126.—Mange Mite of the Pig (_Sarcoptes scabiei_, var. _suis_),
seen from the dorsal surface. × 200.
]
The itch, or mange (scabies), is caused by the irritation which the
mites continually exert on the skin. The warmer the surroundings of the
host, the more active the mites, and the more painful the skin disease.
(The scarcoptes mites, _e.g._, are most unendurable in man when in bed,
and scabby sheep are most tormented when in a warm fold.) The mites
multiply with such enormous rapidity that it is easy to understand how a
single fertilized female, transferred to a new host by contact with an
affected animal, is able, in a short time, to make large patches of the
skin mangy. The course of the disease is generally as follows:—Soon
after infection small swellings appear, which become little bladders of
the size of a pin’s head. These burst, and the affected parts of the
skin are quickly covered with a crust formed from shrivelled bits of
skin and dried-up fluid. In many places the attacked parts of the skin
are moist, for the host, in consequence of the severe itching, rubs or
knocks itself. In consequence of the shedding of fluid the hairs stick
together, and later on fall out. The skin thickens, becomes encrusted,
and is thrown into folds, between which there are deep cracks. Among
domesticated animals the sheep is certainly the one which suffers most
from scabies (_Dermatocoptes_), especially as the disease spreads
rapidly in the warm sheltering fleece, which also makes the removal of
the parasites a matter of the greatest difficulty. The wool gets dry and
brittle in the diseased parts, and its fibres become loose, though they
remain attached for a short time, since their tips are glued together by
the sticky substance which exudes from the little thickenings in the
skin. They gradually fall out, however, leaving the skin covered with a
thick brownish crust, looking as if it were soaked with oil. Badly
infested sheep get thin and even die. This, however, is not usually the
case, and the injury consists in the great deterioration of the wool,
both as regards quantity and quality.
The following summarizes the kinds of scabies affecting man and domestic
animals, and indicates how far one kind of host can affect another:—
Itch of =Man= (_Sarcoptes_) can be caught by the dog, but by no other
domestic animal.
Scabies of the =Horse=.—The sarcoptes mange of this animal is contagious
for man, and for the ox, but no other domestic animal. The dermatocoptes
mange (found more particularly on the inner sides of the legs, and on
the genital organs, tail, and mane) does not spread to man or to other
domestic animals. Nor is this the case with the dermatophagus mange of
the horse (on the fetlocks and adjacent parts of the legs).
Scabies of the =Ox=.—The dermatocoptes mange of the ox (chiefly
affecting the sides of the neck and root of the tail) spreads to men and
horses, but not to sheep. The dermatophagus mange (principally on the
root of the tail and near the anus) does not seem to be transmitted to
man, horse, pig, or dog.
Scabies of the =Sheep=.—The dermatocoptes mange of sheep is not
transmitted as a permanent disease to man, nor to other domestic animals
(with the exception of the goat). The sarcoptes mange of the sheep
(chiefly on the head) causes the itch in man.
Scabies of the =Pig= (_Sarcoptes_) is contagious for the dog, and causes
an eruption in man.
Scabies of the =Dog= (_Sarcoptes_) can be caught by man, pig, and horse.
Scabies of the =Cat= (_Sarcoptes_) is contagious for man, horse, ox,
dog, and rabbit.
Scabies of the =Rabbit= (_Sarcoptes_) is contagious for man, but this is
not so with the dermatocoptes mange, which flourishes in the external
passage of the ear in the rabbit.
Scabies of the =Fowl= (_Sarcoptes_), which affects the legs of hens,
causing thickening of the skin and formation of large spongy crusts, may
infect horses. Hen-houses should not be built in stables.
_Remedies._—From the foregoing facts relating to the transmission of
scabies from one host to another, the preventive measures at once
follow: A mangy animal must not be allowed to come into contact either
with another animal of the same kind or with an animal of any other
kind for which the disease in question is contagious. If scabies
appears in a few members of a flock or herd, it is absolutely
necessary to separate the healthy animals from the sick ones,—and it
is further necessary to cleanse and disinfect places where mangy
animals have been kept, as well as implements or machines which they
have touched, before sound animals are brought near such things.
Cleansing of folds, etc., with hot water, followed by six weeks’
disuse. Cleansing of infected implements with hot soda and water. The
first important thing to ascertain is whether a sick animal, which has
the external symptoms of scabies, is really affected; in order to
determine this the mange-mites must be found. If the mites cannot be
found on the suspected animal, it must be brought into a warm stall
and covered over; especial care must be taken to warm the places where
the skin seems worst attacked; warmth makes the mites more active, and
induces them to come to the surface. Sarcoptic mites are the worst. I
will deal but briefly with the treatment of mangy animals, as it is
usually best to obtain the advice of a veterinary surgeon. _External_
applications must naturally be employed. It appears from the
investigations of _Vogel_ that corrosive sublimate and arsenic kill
the mange-mites less rapidly and therefore less surely than creosote,
carbolic acid, benzine, tar, caustic potash, and tobacco, or even soft
soap. _Zürn_ recommends a thorough smearing of soft soap on the parts
affected. The soap is allowed to remain for some time, even for a
whole day, the infested spots are then rubbed with hot water, and
brushed, if possible, until the crust on the skin disappears. Other
remedies may now be employed. As such, Zürn mentions creosote, diluted
with spirit or oil (1 : 25). Also, among other things, the following
are recommended—benzine shaken up with water (1 : 5–10), or a solution
of 1 part caustic potash in 30 to 40 parts of water. The above and
several other remedies can be used with good results in combating
scabies in most of our domestic animals. But there is more difficulty
with sheep than with other animals, for the fleece is a hindrance to
the beneficial action of the wash employed. It is not possible to make
the sheep quite healthy so long as they remain unshorn. Till then, the
efforts made must be directed to preventing the _spread_ of the mange.
This is managed in the following way. The crust is scraped from the
parts attacked, after the loose wool which covers them has been
removed. The mangy places are then rubbed with a decoction of tobacco
leaves with carbolic acid (1 part carbolic acid to 15 parts spirit and
60 parts water), or with some other of the remedies named above. When
the sheep are shorn, first dip them in a solution (2 parts soda, 1
part lime, and 50 parts water) by which the crust on the affected
places is softened; twenty-four hours later dip in a solution which
will kill the mites. A decoction of tobacco (1 part tobacco to 12
parts water) may be used for this purpose, using for each sheep about
1¾ pints of the fluid, to which has been added 6½ drams carbolic acid
and 6½ drams alcohol. The first washing must be followed by a second,
for the fluid destroys only the mites and not their eggs. As the young
mites are hatched out in three to seven days, the dipping must be
repeated seven days afterwards.
Family: =Ixodidæ= (_Ticks_).
[Illustration:
FIG. 127.—The Dog Tick (_Ixodes ricinus_).
]
Ticks are generally rather larger than the mites of the preceding
family. The skin is tough as leather. The front part of the body is
covered by a hard shield above; the skin of the hinder part, though
tough, is very extensible. The front end bears a sucking apparatus
formed by the pointed jaws, and by its means the tick pierces the skin
of man or animals and holds on fast. Ticks are chiefly found in sandy
soil, among bushes and shrubs, or among herbs. As long as they remain on
the ground they are tolerably small (⅒ inch) and very active. They creep
up haulms and branches, and rest in a suitable spot till a mammal or
bird passes, when they attach themselves to its hair or feathers by
their legs, and bore into its skin with their sharp mouth-parts. Having
thus fixed themselves, they suck the blood of their temporary host. The
walls of their stomach and intestine are extremely elastic, so that the
tick, which at first is only about one-tenth of an inch long and
one-sixteenth of an inch broad, becomes as big as a pea, or even a
garden bean. When the tick has sucked itself as full as possible, it
withdraws its mouth-parts from the skin of its host for the time being,
and lets itself fall to the ground, where it lies for many weeks without
feeding. The small and feeble legs of the tick are not able to move the
heavy, blood-filled body, and movements do not take place for some time,
till the greater part of the imbibed blood has been digested and the
tick has shrunk once more to its normal size. What has been said about
the habits refers only to the female; the much smaller male never seems
to pierce mammals, and its food is not known. In pairing, it is found
attached to the under side of the female, remaining there several days,
even when the female is fixed to the host. Egg-laying does not take
place till the host is quitted. As ticks draw blood from their host
their presence, in spite of the fact that they remain but a short time,
is not a matter of indifference, especially if large numbers affix
themselves to one animal. Sheep and cattle become thin if daily attacked
in the meadows by many ticks. The piercing of the skin causes a stinging
sensation, followed later on by itching of the parts to which the ticks
are attached. The ticks which are fixed must never be seized and pulled
out, for the mouth-parts are so deeply imbedded in the skin that it is
impossible to remove them by force, and the attempt would only result in
tearing the body from the mouth-parts. A better plan is to put a drop of
oil or tobacco water, or, still better, benzine, on the tick, when it
will loosen itself. We distinguish between the =Dog Tick= (_Ixodes
ricinus_), the =Sheep Tick= (_I. reduvius_), and the =Ox Tick= (_I.
reticulatus_), which, however, are not found exclusively on the animals
after which they are named. The first, although found most commonly on
the dog, attacks men who force their way through underwood (hunters),
and in the same way fixes on sheep and oxen. The last two species are
chiefly, but not exclusively, found on sheep and goats.
Family: =Gamasidæ= (_Beetle Mites_).
Beetle mites are temporary parasites on insects, reptiles, and birds.
They have no eyes, but possess shear-like jaws, and tolerably long hairy
legs. The =Beetle Louse= (_Gamasus coleoptratorum_) lives on dung
beetles, sexton beetles, etc.
The =Fowl Mite= (_Dermanyssus gallinæ_) is the size of a sand grain, and
blood-red or red-brown in colour. During the night it is found in large
numbers on the fowls, but during the day hides on the perches, in the
nests, and particularly in the chinks and crannies in the walls of the
poultry-house, also in dung. It draws much blood from the fowls, and
disturbs their sleep by producing a constant itching, the result being
that they get very thin. _Remedy_: Whitewash the fowl-houses twice a
year (autumn and spring) with hot lime to which 5 per cent. of carbolic
acid has been added. The wooden parts should be scalded with boiling
water before whitewashing.
Family: =Trombidiidæ= (_Running Mites_).
Body four-cornered or longish oval; legs tolerably long, hairy; jaws
claw or needle-shaped; surface of the skin velvety; colour reddish or
yellowish. They run about with great rapidity on the ground, tree
trunks, leaves, etc. Most species feed on the juices which they suck
from insects, or from other arachnids.
The =Plant Mite=, or =Red “Spider”= (_Tetranychus telarius_),
is ovoid, at most one-fiftieth of an inch long; reddish (also yellowish
or brownish), with a dark spot on each shoulder. Plant mites are often
found in considerable numbers during the summer, especially on the under
sides of the leaves of low-growing plants; on garden beans, turnips, and
hops; on several ornamental plants, grasses, and various weeds; on
roses, limes, horse-chestnut trees, elms, willows, and fruit trees. In
some exceptionally dry summers the mite increases to such an extent as
to become a great pest. On the upper sides of the infested leaves there
is to be seen, besides the adult and immature mites, a whitish, mealy
substance, consisting of the cast skins and whitish eggs. Many of the
mites run about here and there, but most of them remain fixed, and suck
the sap. All are covered by a delicate web, which is formed by the
animal. The attacked leaves become limp, shrivel up, die, and fall off.
In dicotyledonous plants the withering generally commences in the axils
of the veins. The infested plants often die off gradually, but death may
also take place with great rapidity. Annuals are often killed by the
attacks of the mite. The mites pass the winter in the ground, under
fallen leaves, under the bark of trees, etc.
CLASS IV.: =CRUSTACEA= (CRUSTACEANS).
The Crustacea breathe by gills, and are therefore suited to an aquatic
life. A few species, however, live in damp earth, or in places where the
air is damp (wood lice). Crustacea have two pairs of antennæ, and a
large number of appendages arranged in a characteristic way, but
differing very much in shape in the different groups; skin usually hard
and thick. Lobsters, crayfish, crabs, wood lice, and the small
sand-hoppers, water-fleas, etc., belong to the Crustacea. No Crustacean
is harmful agriculturally.
=Third Sub-Kingdom: VERMES= (WORMS).
Worms[3] are bilaterally symmetrical animals, in which the body is
enclosed in a “dermo-muscular tube.” Under the delicate epidermis there
is found a layer, which does not, as in the higher animals, consist
exclusively of dermis, but is partly composed of muscle-fibres, which
form a distinct coat internally. Worms are able to move by contracting
the various components of the dermo-muscular tube thus formed. In some
worms limbs assist in the movements, but in others this is not so; in
any case, however, the limbs play a relatively subordinate part. These
limbs, which are only present in the bristle-worms, are small, always
unjointed, foot-stumps, which bear bristles. Leeches and some other
worms possess suckers by which they can attach themselves, and move by
alternately contracting and extending their bodies.
Footnote 3:
In ordinary language one understands by “worms” elongated, cylindrical
animals; and several insect larvæ (_e.g._ “wireworms,” p. 103) have
the name applied to them. But to zoologists all “worm-shaped” animals
are not worms, nor have all worms an elongated cylindrical shape
(liver-fluke).
There are segmented and unsegmented worms (thread worms, liver-flukes);
the degree of segmentation is also very various. In many tapeworms each
joint may be regarded as an individual animal. The joints of other
segmented worms (earthworms) do not become detached, like those of
tapeworms, for the purpose of reproduction. The nervous system is absent
in the lowest worms; in the higher worms ganglia always constitute its
central parts, and in annelids these are arranged in pairs on the
ventral side of the body, and united by nerve fibres into a ventral
cord, which is connected in front with a nerve ring surrounding the gut
and thickened above into cerebral ganglia. In many worms (_e.g._
tapeworms and flukes) the nervous system is of much simpler structure.
The sub-kingdom of worms contains a very large number of forms. It is
only necessary to mention here representatives of three classes:
Segmented worms (_Annelida_), round worms (_Nematelminthes_), and flat
worms (_Platyelminthes_).
CLASS: =ANNELIDA= (SEGMENTED WORMS).
Segmented worms with rounded (earthworm) or flattened (leech) bodies,
and possessing both mouth and anus. They fall into two sub-classes: I.
Leeches (_Discophora_), II. Bristle-worms (_Chætopoda_). The first
possess suckers as organs assisting locomotion, the latter foot-stumps,
which bear longer or shorter bristles; but these foot-stumps may be
absent, and the bundles of bristles are then simply imbedded in pits.
The latter is the case in the only members of the class which interest
us here, _i.e._ the _earthworms_.
The =Earthworms= (_Lumbricus_).
There are several species in the genus, but all agree in their habits.
The body of the earthworm is slender and cylindrical, tapering in front
and somewhat flattened behind. On the ventral side of the second segment
is found the opening of the mouth. There are no eyes, though these
animals are sensitive to the action of light. The earthworm is
hermaphrodite (p. 16); when two individuals pair they mutually fertilize
each other. On a warm summer evening two adjacent worms creep half out
or nearly out of their burrows, and apply the front parts of their
bodies together, especially a reddish, swollen part found at about the
middle of the anterior half of the body. In this region the glands in
the skin are very strongly developed, and secrete a substance which
surrounds the eggs as a capsule as they are being laid. Earthworms are
chiefly found in damp humus, or, at any rate, not in very poor sandy
soil or clay. From time to time they carry their burrows up to the
surface in order to get rid of the undigested remains (“worm castings”)
of the humus and vegetable matters which have been taken into the body.
The burrows run down obliquely into the soil, or more rarely vertically,
to the depth of eight feet or more; they end in an enlargement, where
the worm remains coiled up during the winter, after having closed the
mouth of the burrow with a plug of leaves, twigs, paper, straw, etc.
Although the earthworm chiefly subsists on the organic matters found in
earth rich in humus, it also devours the leaves of cabbage, onion, and
other plants, and especially seedlings (particularly those of beet). It
draws these parts of plants about four-fifths of an inch into its
burrow, and moistens them there with an acid fluid it secretes, and
which acts upon them before they are taken into the body. Earthworms may
effect considerable damage by destroying seedlings, particularly in damp
fields, though this damage is always local. A not inconsiderable amount
of benefit is to be set against this. By means of the burrows which they
dig earthworms cause air to penetrate into the soil much better than it
could otherwise do, which is known to be of the greatest importance for
plant life. Earthworms are extremely important owing to the large
numbers in which they are present in the soil, and for another reason
besides the one just given. Darwin shows that in many parts of England a
weight of ten tons of earth per acre passes through the bodies of
earthworms, and is brought to the surface by them, so that in a few
years the entire humus-containing surface layer of earth has passed
through their bodies. They therefore prepare the soil in an excellent
manner for the growth of plants, by continually exposing it to the air.
They cause stones to sink in the soil by throwing out at the top earth
which naturally consists only of particles small enough to pass through
their intestines. They play the part of gardeners by thoroughly mixing
together the particles of soil, and bury under their castings, in a
shorter time than one would imagine, objects found on the surface of the
soil (bones, oyster-shells, dead animals, leaves). Plantfood is quickly
formed again from these buried matters. Earthworms, therefore, play a
very important part in the economy of nature; indeed, many regions, now
occupied by luxuriant pastures or fertile cornfields, would be a waste,
had it not been for them. Where, however, in damp spots they injure
seedlings, they may be collected, either during the day after a warm
rain, or in the evening, at which times they lie half out of their
burrows. If a decoction of walnut leaves is poured into these, they will
crawl out. _Enemies_: Mole, shrews, hedgehog, toads and frogs, ground
beetles, rove beetles, mole-crickets, centipedes, etc.
CLASS: =NEMATELMINTHES= (ROUND WORMS).
Body cylindrical, unsegmented; body-wall tough, hooklets or spines may
be present on it, but deeply imbedded bristles are always absent. The
gut may be absent (some parasites), but this is exceptional. There are
no special organs for circulation and respiration. Sexes distinct in the
large majority. I will deal with only one of the orders belonging here.
ORDER: =Nematoda= (THREAD WORMS).
[Illustration:
FIG. 128.—Diagrammatic transverse section through the body of a Thread
Worm, internal organs being omitted: _p_, cuticle and skin; _q_,
muscle layer; _a_, lateral lines; _b_, dorsal and ventral lines.
]
Elongated, thread-shaped or spindle-shaped, unsegmented. A gut,
terminating in a ventral anus, is present. Outer investment of the skin
smooth, often weakly ringed or striated. The muscle layer underlying the
true skin is interrupted here and there, where the skin itself stretches
further inwards. In this way are distinguished the _lateral lines_ or
_fields_ (Fig. 128, _a_), which run right along the sides of the body,
dividing it into a dorsal and a ventral region. There are often present
as well two smaller but similar _dorsal_ and _ventral lines_,
respectively situated above and below (Fig. 128, _b_). Mouth usually
surrounded by lip-like folds, but more or less distinct jaws may also be
present. The anus either lies at the apex of the tapering posterior end
of the body (_trichina_), or further forward, on the ventral surface.
Among the Nematodes are included a number of relatively small species,
living free in the earth, and sucking plant parts, while other forms
fairly closely related live parasitically in plants, and often cause
very serious plant diseases (_e.g._ Beet Eelworm); a larger number of
species are parasitic in animals. The free forms and those parasitic in
plants lay relatively few, but very large, eggs, although, in several
species, increase is furthered by a succession of many generations in
the year. The Nematodes parasitic in animals lay very numerous eggs,
even several millions. Harmful species are known from the following
families: 1. =Palisade Worms= (_Strongylidæ_), 2. =Whip Worms=
(_Trichotrachelidæ_), 3. =Slender Thread Worms= (_Filaridæ_), 4. the
=Round Worms= (_Ascaridæ_), 5. =Eelworms= (_Anguillulidæ_).
I will successively treat of the harmful forms, but since many species
belonging to different families infest the digestive organs of the
different domesticated animals, causing similar symptoms of disease
which may be dealt with in much the same way, the following general
sketch is first given:—
=Nematodes in the Gut= (more in young animals than old) cause the
following _symptoms_: (1) Appetite variable. (2) Nutrition in general
affected, even if sufficient food is taken; constipation or diarrhœa;
belly much drawn in or else, and usually, swollen out. The animal itself
is thin, and has (except horse) a tendency to vomit. (3) An itching all
over the body, especially at the nostrils and anus. The animal rubs and
bites the sides of its body. (4) Tongue covered with a thick, soft,
yellowish coating. A sweet smell from the mouth. (5) The skin is tense,
lacking its usual elasticity. (6) The animal suffers from spasmodic
colic, and (7) disturbances of the nervous system (whining or crying;
unrestrained or suppressed fits). _Remedies_: Horses and cows infested
with thread worms may be given chopped carrots, beets, and turnips,
previously mixed with sugar or crushed sugarcandy. Roasted oats are also
good. For sheep finely crushed glass, kneaded into pills with bread,
will always suffice. Gritty sand in the food may also be of use. Pigs
should be given sour milk, acorns, unripe cheese, horseradish. For dogs,
sausages containing garlic, as much flesh food as possible, strongly
salted food, milk boiled with garlic. In all cases iron may be given.
The advice of a veterinary surgeon should be sought in the matter of
medicines (tansy, male fern root, tartar emetic, arsenious acid, etc.).
Family: =Strongylidæ= (_Palisade Worms_).
Spindle-shaped; anus on the tip of the hind end of the body; in all
thread worms the rectum and male sexual organs open by a common cloacal
opening, which, in the palisade worms, is surrounded by an umbrella, or
cup-shaped apparatus (_bursa_), kept expanded by means of muscular ribs
(Fig. 129).
Here belong—
The =Giant Palisade Worm=, or =Strongyle=, (_Eustrongylus gigas_).
Female from a foot to thirty-nine inches long, and as much as two-fifths
of an inch thick. Male six to sixteen inches long; reddish. Lives in the
cavity (pelvis) of the kidneys in horses, oxen, dogs, and man; causes
degeneration of the kidneys, with blood in the urine, nervous diseases,
and disturbance of the feelings and intelligence.
[Illustration:
FIG. 129.—Tail of male _Strongylus armatus_, strongly magnified.
]
The =Armed Palisade Worm=, or =Strongyle= (_Strongylus armatus_),
four-fifths of an inch to two inches long, one twenty-fifth to
one-twelfth of an inch thick; reddish brown. Taken into the gut of the
horse with the drinking water as a young, minute worm, it bores through
the walls of this organ into the blood-vessels branching there. Later on
it bores into the walls of the larger arteries of the hinder part of the
body, especially into those which carry blood to the wall of the gut
(particularly anterior mesenteric artery). At those parts of the
arterial walls where it collects in large numbers, swellings (aneurisms)
are produced, varying from the size of a pea to that of a hen’s egg. A
constriction is often developed quite close to this swelling, and a plug
of fibrin may also be formed within the artery, so that the circulation
in the wall of the gut is greatly hindered. As a result of this the
glands and muscles in the wall of the digestive tube refuse their
office, so that regular digestion and onward movement of the food do not
take place. This leads to colic. As soon as the strongyloid larvæ have
become adult, they pass from the walls of the arteries into their
cavities, and are carried by the blood-stream to the walls of the gut,
which they penetrate in order to reach its cavity, where (cæcum and
large intestine) they pair, after which the female lays eggs, which are
carried to the exterior in the dung. The quickly hatched young seek
water, mud, or damp earth, where they live until, by some means (_e.g._
with the drinking water) they manage to enter the gut of a horse or
(more often) ass. _Preventive Measure_: Horses and asses must not be
allowed to drink stagnant water.
The =Stomach Palisade Worm=, or =Strongyle of the Sheep= (_Strongylus
contortus_). Male one-half to two-thirds of an inch, female
three-quarters to four-fifths of an inch long; whitish or reddish,
somewhat coiled at both ends. The disease of the stomach, and diarrhœa,
which affect lambs, usually in spring, and result from the presence of
these worms in large numbers in the true or fourth stomach, lead to
emaciation, weakness, and poverty of blood. Development unknown.
Nutritious food will cure lambs which are not very badly infested, but
hastens the death of those which are.
The =Lung Worm= of Lambs (_Strongylus filaria_). Male an inch, female as
much as three and a half inches long, thread-shaped, white or yellowish.
It appears that the young worms are taken into the stomach of a lamb (or
sheep) with the drinking water; they are found there in May, June, and
July. They quickly climb back into the throat, from which they get into
the windpipe and its branches. There they penetrate the mucous membrane,
where, until they have reached the sexual stage, they are found imbedded
in small swellings, which they quit at the end of winter or the
beginning of the next spring, if their host lives so long. The female
bears living young, which as very minute worms may be met with by the
hundred in the mucous lining the windpipe and its branches. A direct
transference of the parasite from one sheep to another does not take
place, since the young born in the mucus secreted by the walls of the
air-tubes must first live and grow for some time in water or slime
before they are able to undergo further development in the body of a
sheep or lamb. The fate, however, of the young worms which pass to the
exterior in the mucus is not yet sufficiently known. _Symptoms of
Disease_: Running of slime from the nose, difficulty of breathing,
cough, emaciation, poverty of blood. Death ensues in from two to four
months. Recovery only of very strong individuals infested by
comparatively few parasites, most of which they cough out. _Preventive
Measures_: In regions where the evil is very prevalent the young sheep
must not be allowed to go into the meadows. If it is impossible to keep
them penned in, a little food and water may be given before sending them
to pasture in the morning. In this way the danger of infection will be
somewhat lessened, since it is then less likely that the animals will
eagerly betake themselves to pools and ditches in order to quench their
thirst. Since during the months May to July the young worms (most
probably taken in with the water drunk) are found in the stomach, it is
good during this time to give vermifuges to the lambs and sheep. For
medicines a veterinary surgeon should be consulted.
The =Small-tailed Palisade Worm=, or =Strongyle= (_Strongylus
micrurus_). Thread-shaped; male one and two-fifths, female two and
two-fifths to two and four-fifths of an inch long; lives in oxen
(especially calves) in swellings of the arteries, also in the windpipe
and its branches. Severe bronchitis.
Family: =Trichotrachelidæ= (_Whip Worms_).
Small, slender, elongated worms, with the anus or, in the male, cloacal
aperture at the hinder end of the body; the latter, however, is not—as
in palisade worms—surrounded by an umbrella or cup-shaped expansion.
Here belongs:
=The Trichina= (_Trichina spiralis_).
[Illustration:
FIG. 130.—Encapsuled Muscle Trichinæ in flesh, strongly magnified.
]
[Illustration:
FIG. 131.—Male Intestinal Trichina, strongly magnified.
]
In the sexual condition this lives as a minute worm (male
one-seventeenth, female one-eighth to one-sixth of an inch long), the
so-called “intestinal trichina,” in the gut of human beings and
carnivorous mammals. In this situation it brings forth living young
(some fifteen hundred in number), and the multiplication is enhanced by
the fact that of the very numerous trichinæ found in the gut there are,
on the average, about twelve females to every male. The young trichinæ
bore into the walls of the gut, and are carried by the blood-stream into
the muscles. At first each little worm extends itself longitudinally in
a muscle fibre, but, as it gets larger, curves and becomes spirally
twisted, so that the sheath (sarcolemma) of the fibre is bulged more and
more outwards. The growth of the young trichina is very rapid—an
individual only ¹⁄₂₅₀ of an inch long before leaving the gut may attain
the length of one twenty-fifth of an inch in fourteen days. It then
grows no more, and the sheath of the muscle fibre gradually thickens to
form a capsule or cyst. Later on, in about a year, lime is deposited in
the capsule. The “muscle trichinæ” retain their vitality for several
years. If now the host of the muscle trichina is devoured by any other
mammal, the capsule is digested in the stomach of the latter, and the
once more liberated worm becomes a sexually mature “intestinal trichina”
in a few days. The pig is the ordinary host of trichinæ, which (without
the intervention of any other host) can be permanently parasitic in this
domestic animal, since pigs often devour swine’s flesh. They often
enough devour even their own young, and, especially in large
slaughterhouses, swine are often fed with the offal of their companions.
The trichinæ also spread through the body of any living being (men,
rats) which eats trichinous pork. The trichinæ thus introduced cause, in
the human subject, a dangerous or even fatal disease known as
_trichinosis_. The size of this book does not permit me to describe the
symptoms of this complaint in man. Pigs suffer much less from the
parasite; they may even contain an enormous number of trichinæ in their
muscles without being noticeably ill. Symptoms of disease, however,
often appear more or less clearly. A short time after eating the
trichinous meat the appetite of the pigs is bad; they appear in bad
spirits; the tail straightens out, and they often remain standing with
bent limbs and arched backs. There may be, in addition, pains in the
abdomen, diarrhœa, and fever. Later on, when the trichinæ have settled
down in the muscles, the pigs suffer from stiffness in the legs and
tenderness in the loins; they often cry out in pain. After this,
however, health and appetite may return, and they can be fattened.
Trichinous swine therefore appear quite sound, and are slaughtered in
due course. The trichinæ in the pig are found most abundantly in the
diaphragm, the masticatory, eye-, and other muscles of the head, also in
those of the neck, larynx, abdomen, and loins. The fore part is more
infested by trichinæ than the hinder part, but in very bad cases they
are found everywhere, even in the hams. _Remedies_: (1) The swine must
be prevented, as far as possible, from taking up trichinæ, and therefore
must never be given the offal from other slaughtered swine. The flesh of
trichinous swine should be burnt, and not buried, lest dogs or other
animals should eat it and spread trichinosis. (2) Care must be taken
that no trichinous pork is eaten by human beings (microscopic
examination; meat inspection). Pork (or sausages) must never be used raw
or half cooked. Trichinæ are killed by a temperature of 140° to 150° F.
The _inside_ of the piece of meat must be exposed to this temperature.
Family: =Filaridæ= (_Slender Thread Worms_).
Elongated and thread-shaped. Round mouth. Do not infest the gut or other
cavities, but the tissues of the body, chiefly connective tissue. None
of the species require notice here.
Family: =Ascaridæ= (_Round Worms_).
Relatively shorter than the worms of the preceding family. Mouth
triangular, surrounded by three teatshaped lips. In the male the hinder
end of the body is usually bent in a hook-like manner. The anus is not
placed quite at the hind end of the body. All the species inhabit the
alimentary canal (Cf. p. 211).
=Horse Worm= (_Ascaris megalocephala_). Male six to eight, female twelve
to seventeen inches long; sometimes occurs in great balls, causing
stoppage.
=Round Worm of Cat= (_Ascaris mystax_). Male two to two and two-fifths,
female four and four-fifths to five and one-fifth inches long; in the
intestines of the cat. _Ascaris marginata_ infests the dog.
=Pinworm= (_Oxyuris curvula_). Male one-fourth to one-third, female one
and four-fifths of an inch long. In the rectum of the horse, causing
persistent itching.
Family: =Anguillulidæ= (_Eelworms_).
Extremely small, thin-skinned; lay only a few relatively large eggs,
which develop very quickly. With few exceptions either earth eelworms
(_i.e._ live in decomposing organic matter or humus soil) or as plant
parasites leading to characteristic diseases of wild and cultivated
forms. All these parasitic forms have a “mouth spine.” This structure,
found in the mouth cavity, is very sharp and pointed in front, and can
be worked forwards and backwards so as to penetrate the cell walls of
plants. A mouth spine is not only found in the species which infest
plant tissues (several species of _Tylenchus_ and _Aphelenchus_, as well
as all the known species of _Heterodera_), but also in those forms
living free in the earth which bore into the exterior of plant roots
(the remaining species of _Tylenchus_ and _Aphelenchus_, _Dorylaimus_,
etc.). In all cases an eelworm, devoid of a spine, is not a plant
parasite. I will only deal with those parasites by which well-known
destructive diseases of cultivated plants are caused. These belong to
the genera _Tylenchus_ and _Heterodera_. The first remain eel-shaped
throughout life, but the adult females of the latter swell out
considerably and become lemon- or pear-shaped.
The =Stem Eelworm= (_Tylenchus devastatrix_).
Length one-thirtieth to one-fifteenth of an inch long, usually of
intermediate size; the two sexes of approximately equal length. Live and
reproduce in various cultivated plants (_e.g._, rye, oats, stored
onions, hyacinths, buckwheat, potatoes, clover, fuller’s teasel) and
wild plants (_e.g._, _Poa annua_, _Anthoxanthum odoratum_, _Dipsacus
silvestris_, _Polygonum persicaria_), but not to the same extent in all.
It must also be added that eelworms of which the progenitors have
developed for a considerable number of generations in the same plant,
are not easily transferred to another kind of plant, or at any rate do
not multiply vigorously there. Eelworms, of which the ancestors have
lived for many years exclusively in rye, or alternately in rye and
buckwheat, do not readily pass over to seedling onions, and first only
reproduce in them to a small extent. The eelworms live only in stems,
branches, and leaves, never in roots. In the places where they have
penetrated the plant tissues an abnormal growth in thickness of the
parts involved takes place, while the growth in length is either much
diminished or even entirely stopped. Also the chlorophyll disappears
sooner or later from the attacked spots, and rapid death generally
ensues. Since only those parts of an organ which are inhabited by a
large number of eelworms swell much, it is obvious that cracks are often
developed in the stems and leaves concerned. It is further easily seen
that the species and constitution of the infested plants will have an
important influence on the progress of the disease caused by the
eelworms. But since several generations of this parasite succeed one
another during the same year, the resulting malformation is usually very
considerable. “Clover sickness” is probably due to this eelworm.
I will treat in somewhat greater detail the =Eelworm Disease= of rye,
which is largely prevalent in Westphalia and the Rhine provinces, and
had already made its appearance, in the latter at least, at the
beginning of the century.
The eelworms producing the disease migrate into the soil on the ripening
or death of the grain, and later on go back to the new young rye plants
or to other plants in which they can live, as the case may be. It is
therefore clear that (1) where this disease exists the soil is infected
for a time, and (2), the eelworm disease of rye principally appears in
regions where the culture of rye is carried on to excess. Germination of
the seed corn goes on quite normally in infected fields, and it is only
exceptionally that anything particular is noticed in the young plants of
winter rye during autumn and winter. The disease appears at the
beginning of spring. Some plants soon become yellow and die: others
appear to grow very luxuriantly; they possess a beautiful bluish-green
colour and seem very healthy; later on they develop enormously in
breadth, and each separate plant covers a relatively large area. The
base of the stem swells abnormally, so that the plant looks as if it
bore below an onion projecting above the ground. This is caused by the
lower joints of the haulm remaining very short and thickening
considerably, causing the leaf-sheaths which surround the base of the
stem to become thicker and broader than usual. The feeble development of
roots is also characteristic. The leaves generally remain short, but get
very thick; they often become wavy, and may even appear frilled. All the
leaves, however, are not crumpled in this way; a few remain quite
normal, while others are small and grass-like, but thick (Fig. 132).
Later on, the tip of the haulm and the ear often do not come out of the
leaf-sheaths; in other plants the ear may appear, but remains small and
deformed as well as the rest of the haulm, while the grains which
develop are small. A number of shoots, however, may develop normally and
bear fruit. Badly infested plants quickly die, some at the very
beginning of spring, others later.
[Illustration:
FIG. 132.—Rye plant in the later stage of the Eelworm disease.
]
Where the disease is very bad it may easily be recognized by its
characteristic distribution. A number of bare places are noticed in
spring on the infected fields; round about these places still living but
badly diseased plants may be noticed, and the symptoms of attack are
less obvious the further one goes from the bald spots.
On the death of the rye plants the eelworms mostly travel back to the
soil, but sundry eggs and larvæ stop in the dried-up remains. Rye straw
may further infect a diseased field by getting into farmyard manure and
being brought back again with it; for the eelworms (at any rate as eggs
and larvæ) are killed neither by drying nor by the action of dung and
other decaying substances. Strongly infected spots (bare patches) on an
infested field are usually the places where dung containing diseased
rye-straw has lain for some time. From such centres the spreading of the
eelworms takes place: (1) _actively_ by the migration of the worms, (2)
_passively_ by rain, the feet of labourers, the hoofs of horses, field
implements, etc.; also (on loose soils) by the wind, which not only
blows about particles of earth, but also the dried-up larvæ which are
always found on the surface of the ground. As the eelworms multiply very
rapidly whenever they are in the plants, and as the means of
distribution are very numerous, the disease spreads with great rapidity.
_Remedies._—Proper rotation; limitation of the culture of rye, growing
in place of it carrots, turnips, or lupines. Now and then (but not too
frequently), potatoes, buckwheat, clover, and oats may be cultivated in
the fields affected, at any rate before sowing rye again. Abundant
manuring, especially with sulphates of potash, ammonia, and iron. Deep
cultivation of the soil, since the eelworms find no food in the deeper,
damper layers of the soil, nor can they pass into the dried condition,
and so must die.
=Oats= suffer from eelworms just in the same way as rye.
=Clover Sickness= is marked by short stunted shoots, and whitish rounded
buds, often remaining closed; also by the whitish colour and abnormal
thickening of the shoots and buds.
=Eelworm Disease of Potatoes.=—Crumpling and small growth of the parts
above ground. In many cases there may even be no potatoes at all, or
only small ones, poor in starch, though sometimes they may be tolerably
large. On the surface of the tubers there are discoloured rotten spots,
not penetrating deeply, and usually (but not always) at the attached
end. These dark patches contain the eelworms.
=Eelworm Disease of Buckwheat.=—Joints of the stem for the most part
much thickened, but abnormally short. In many cases a large amount of
branching in the lower part of the stem, usually at a place where it
bears a nodular swelling. Branches generally short. There may be twists
and bends in the stem and branches. Often, but not always, the formation
of flowers and fruit is stopped. The thickened parts of the stem are
brittle; they contain the eelworms in their interior.
The =Wheat Eelworm= (_Tylenchus scandens_ = _T. tritici_).
[Illustration:
FIG. 133.—Ear Cockles of Wheat; the third shows the eelworm larvæ on
its cut surface.
]
Length of the male about one-twelfth of an inch, of the female one-tenth
to one-fifth of an inch (according to the size of the galls in which the
eelworms develop). The wheat eelworm is the cause of “ear cockles,” also
known as “peppercorns” and “purples.” In several parts of the ear short
thick dark brown galls (Fig. 133), resembling the seeds of corn-cockle,
are found instead of wheat grains. Inside the thick brown shell there is
a yellowish white mass, containing hundreds or even thousands of eelworm
larvæ (one thirty-first to one twenty-seventh of an inch long). These
are quite dry and rigid, but gradually revive on moistening, even if the
black galls have remained twenty years in the dried-up condition. When
the wheat is ripe the dark-walled galls are gathered in with the crop,
and in many cases are sown again with the sound grains. The brown shell
then decays, and the eelworm larvæ leave the gall, travelling to a
neighbouring wheat seedling, where they live between leaf-sheath and
haulm, also penetrating into the terminal bud. The haulm of a wheat
plant infested by many eelworms remains relatively short, the leaves are
often sharply bent and have wavy margins. Wheat plants thus infested
closely resemble rye plants diseased in a similar way, but are much less
deformed. This is because the wheat eelworms do not reproduce till they
reach the ear, and there is consequently only one generation per year,
while several generations of eelworms succeed one another in the same
rye plant. The eelworms quickly travel from all parts of the plants into
the ears, and get into the rudiments of the flowers, causing them to
swell up like bladders, and their walls to become first dark green, and
then dark brown. Sixteen to twenty eelworms are present in the lowest
flowers of the ear, ten to twelve in those higher up (and therefore
smaller), and four to six in the topmost (smallest) ones. Soon after
entering the flowers the eelworms become sexually mature, and lay eggs
(600 to 1600), from which are developed the larvæ that inhabit later on
the cockle-seed like galls. The disease is known in England, Germany,
France, and Italy, and is especially harmful in Saxony, where it
sometimes attacks a quarter of the wheat crop. _Remedies_: Either there
should be no ear cockles in the seed corn, or else the eelworms should
be destroyed in them. The infested grain may either be put through a
sieve, or else soaked for twenty-four hours in weak sulphuric acid (one
pint strong acid to thirty-three gallons of water), when many of the
galls float and can be skimmed off, while the eelworms are killed in
those which sink.
[Illustration:
FIG. 134.
(_For Description, see note[4], next page._)
]
Footnote 4:
FIG. 134.—The Beet Eelworm (_Heterodera Schachtii_): 1, A beet root
with adult females attached (natural size); 2, a lateral rootlet of
beet which Eelworm larvæ (_a_) are penetrating (enlarged); 3, a
lateral rootlet of beet with swelling (_a_) of the outer skin caused
by the excessive development of larvæ which have previously entered
it, and which have now become nearly mature females (enlarged); 4, a
just-hatched larva; 5, a larva which has penetrated a root and swollen
up into a club-shaped form; 6–8, development of the male; 9, a nearly
adult and, 10, an adult female. The following letters have reference
to Figs. 4–10: _a_, mouth spine,—_b_, sucking stomach (pharynx),—_c_,
_d_, intestine,—_e_, _f_, rectum,—_f_, anus,—_g_, excretory organ; _h_
(in Figs. 4–7), rudiments of the sexual organs in the undeveloped
larvæ; _h_ (in Fig. 8), testis; _i_ (in Figs. 7 and 8), copulatory
spicules of the male; _k_ (Figs. 9 and 10), ovary; _l_ (Figs. 9 and
10), female sexual opening; _m_, nerve ring; _w__{1} (Figs. 6–8),
larval skin; _w__{2} (Figs. 6–8), new skin which the developing male
forms within the larval skin. Figs. 4 and 5 are magnified more than
Figs. 6–10.
The =Beet Eelworm= (_Heterodera Schachtii_)[4]
is the cause of the “beet sickness” of the soil. The course of the
disease is as follows. At the end of July light-coloured patches are
found here and there among the normally developed beet. The leaves are
weak and limp, and the outer ones especially get yellow, spotted, and
die off. Later on the inner leaves die as well, after which the top of
the beet becomes black and the whole root gradually decays. In less
severe cases the beet may recover towards autumn and develop new heart
leaves, but the roots remain small and the crop is poor, often being
only one-third of its normal amount. Kühn has proved by infection
experiments that the sole cause of beet sickness is a nematode, of which
the life history is as follows. The female is found fixed to the
branches of the root; it is citron-shaped, about one twenty-fifth of an
inch long (Fig. 134, 1 and 10), and contains on an average three hundred
and fifty eggs. Some few of these, together with a jelly-like substance
making up an “egg-sac,” may pass out to the exterior, but the large
majority develop in the body of the female, which ultimately becomes a
mere sac enclosing the eel-like larvæ. The female is killed by the
process. The liberated larva (Fig. 134, 4) seeks out a root (about one
twenty-fifth of inch thick), and bores into it. Here it lives as a
parasite, causing the disease of the attacked beet plant. The larva
quickly sheds its old skin, assumes a thicker form (Fig. 134, 5), ceases
to move, and gradually causes the outer skin of the root to bulge out
externally (Fig. 134, 3, _a_). The distinction between the sexes now
rapidly makes its appearance. A thick motionless larva, destined to
become a male, temporarily ceases to feed, shrinks within its old skin,
develops a thin new one, and ultimately becomes a long eel-like worm
(Fig. 134, 6, 7, 8), which grows into an adult male (8). In the stage
represented in Fig. 134, 8, the animal still lies under the outer skin
of the root, which never bursts during its development, but the mature
male bores out of its larval skin and out of the root, passing into the
soil, where it finds and fertilizes the female, which in the meantime
has developed but remains attached to the root. The female develops in a
simpler way, by the gradual distension and growth of a larva (not by a
process of re-formation) and gradual development of the female sexual
organs. As the larva passes from the stage of Fig. 134, 5, into that of
Fig. 134, 9, and later on into the adult condition, 10, the outer skin
of the rootlet is ruptured, and the female comes out from its tissues,
remaining, however, attached to its outside (Fig. 134, 1). The entire
development from egg to sexual adult takes four or five weeks, and there
may be six or seven successive generations, the reproduction is
consequently very rapid.
It also obviously follows that “beet sickness” of the soil is especially
prevalent in fields where there has been an excessive amount of beet
culture. The disease, however, may suddenly appear in fields which have
been hitherto “safe” for beet, and in many such cases it has been proved
to result from manuring with artificial compost rich in refuse from
affected fields. The disease frequently appears, too, in fields where
beet have never been cultivated, but where cabbage has been grown for a
long time. It has been shown, especially by Kühn’s investigations, that
the beet eelworm can live in many plants both cultivated and wild,
_e.g._ of the former, cabbage, rape, mustard, garden cress, chickling
peas, mangold, oats; of the latter, charlock, spurrey, couch grass.
These researches are of the greatest importance both for understanding
the way in which beet sickness spreads and in combating it.
_Preventive Measures_: Manufactured compost must not be used as a manure
on beet-fields. The refuse from infested beets, if used on other fields,
must be mixed with one-sixth its bulk of quicklime. The boots of
labourers employed in beet-sick fields, the hoofs of horses working in
them, and also the implements used, must be carefully cleansed lest
infected earth should be carried to other fields. _Remedies_: Kühn has
recommended the use of plants which attract the eelworms
(“lure-plants”). He sows on beet-sick land rapidly germinating plants,
of kinds which the worms readily attack, and weeds them out again when
they have become infested by the parasites, but before these have had
time to mature and re-enter the soil. The eelworms are thus allured into
the plants grown, and destroyed with them. Such lure-plants must be sown
as thickly as practicable, so that the soil may be penetrated by as many
slender rootlets as possible. After these plants have been dug up, a
second lot should be grown, since all the eelworms will not have
attacked the first lot; and it is even advisable to grow a third batch.
Kühn used as lure-plants the various kinds of cabbage, also summer rape
(_Brassica rapa_), since this plant has a great attractive power for the
beet eelworms, and can hold a large number of them in its numerous, much
branched rootlets. I cannot go into all Kühn’s researches here, and will
only mention the following. In the course of the year 1880 part of a
beet-sick field had three successive crops of lure-plants grown upon it,
each being dug up from thirty to forty days after sowing. The field was
ploughed in autumn, suitably manured the next spring, and sown with beet
in the middle of April. The other part of the piece of land was treated
in exactly the same way, except that no lure-plants were grown upon it.
A difference was very soon seen between the two plots, and there was a
very great difference at the time the crop was ready to be gathered in.
The plants on all parts of the first plot were in a flourishing
condition, but those on the second plot were in many places either
killed outright or else small and misshapen. The crop succeeding the
lure-plants was three times as great as it had been before, and almost
equal to that of a healthy field. Later on, Kühn made an important
discovery; he found that larvæ which have reached the thickened
motionless stage, depicted in Fig. 134, 5, require a considerable amount
of food to keep them alive, and enable them to develop further. If the
plants are disturbed in such a way as to kill the rootlets containing
the larvæ in this stage, these are unable to develop any further. Kühn
caused a kind of horse machine to be made, adapted for rapidly
destroying the lure-plants in the fields. For further details, his
original memoirs may be consulted.
The =Root-knot Eelworm= (_Heterodera radicicola_).
This second species of the genus _Heterodera_ develops much like the
beet eelworm, living like it on the roots of plants, but more deeply
within them, so that the body of the female (which swells till it
becomes pear- or flask-shaped) does not cause the outer part of the
infested root to project, and does not reach the exterior. Where the
eelworms collect, galls are formed which decay later on, when the
eel-shaped larvæ escape into the soil, very soon, however, to enter the
roots again at their slender tips. The galls are thickenings in the
course of the root, and are never lateral appendages, like, for
instance, the well-known “tubercles” in the roots of leguminous plants
(_e.g._ clover, pea). The root eelworm lives in the roots of more than
fifty plant species in the most various parts of the world, and infests
both weeds and cultivated plants. It is especially damaging to clover
and lucerne, in which not only the galls die, but also all parts of the
root below them. In this country the roots of cucumber and tomato are
sometimes attacked (E. A. Ormerod).
CLASS: =PLATYHELMIA= (FLAT WORMS).
Flat worms have a flat, generally leaf-like body, and usually no
body-cavity, the space between the internal organs and the muscular
body-wall being filled up with connective tissue.
I will only deal here with the orders of Tapeworms (_Cestoda_) and
Flukes (_Trematoda_).
ORDER: =Cestoda= (TAPEWORMS).
[Illustration:
FIG. 135.—_Tænia saginata_: head, and a number of joints, represented
natural size.
]
[Illustration:
FIG. 136.—The Common Tapeworm (_Tænia officinalis_): _a_, head and
neck, strongly magnified; _b_, joints, natural size; _c_, eggs,
strongly magnified.
]
[Illustration:
FIG. 137.—Tapeworm Larva (of _Tænia solium_), much enlarged.
]
[Illustration:
FIG. 138.—The three types of Bladder-worm, diagrammatically
represented.
]
[Illustration:
FIG. 139.—Measle of _T. solium_, with head thrust out (× 6).
]
The external characters of an ordinary tapeworm may be gathered from
Figs. 135 and 136. A very small “head” continued behind into a small
“neck” can be distinguished, and a very large number of joints, of which
the first are very small and short, while those which follow get larger
and larger the further they are from the head. The tapeworm at first
consists only of a head which holds on to the lining of the intestine by
means of suckers or similar structures. The hinder part of the head next
elongates to form the so-called “neck,” and a cross-wall is quickly
developed a little way in front of the hind end of this neck. By this
division is formed the first joint, which, though forthwith tolerably
independent, remains attached to the neck of the tapeworm head, until a
new joint is separated off from the hinder part of the neck, immediately
in front of the first joint. Every new joint is similarly formed by the
constriction of the hinder part of the neck. Each joint possesses a
complete set of hermaphrodite reproductive organs; it becomes sexually
mature without reference to other joints, breaks off, and creeps about,
even for considerable distances, and finally ruptures, so that the
numerous eggs are liberated. Each joint may therefore be regarded as an
individual, though the tapeworm, considered as a whole, also possesses a
certain individuality. The tapeworm is a species of animal which exists
in two forms. One of these is the sexually reproducing joint, which
leaves the original host, and from the eggs of which are developed
larvæ, which become, in another host, _bladder-worms_, or _measles_.
These develop a _head_, which is the asexual second form of the
tapeworm. This, therefore, is a case of metagenesis (p. 16). It appears,
from what has been said, that the head can in no sense be compared to
the head of an ordinary animal; it has neither mouth nor jaws, for
tapeworms do not possess a gut. The head and joints take up osmotically
through their walls the nutritive matter found in the intestine of their
host. There are suckers and, in several species, a circlet of hooks on
the head (Fig. 136, _a_), by which the animal holds fast to the
intestinal wall. Thousands, or even tens of thousands, of eggs may be
produced by a single joint. The joint is liberated when the eggs begin
to ripen, often before. In some species several adjacent joints are
pinched off at the same time. The tapeworm joints leave the intestine of
their host either alone or with the dung. After falling to the ground
they creep along like snails, and attach themselves to various plants.
It is obvious that a tapeworm joint or a number of the eggs produced by
it may easily be taken up by a grazing animal. The eggs of a particular
kind of tapeworm are only able to develop further if they reach the
intestine of a particular kind of host. It is undoubtedly true that, as
a rule, only a relatively small number of the eggs produced by a
tapeworm develop further, but the great powers of reproduction prevent
the species from dying out. If, now, either a joint or the eggs from one
are taken into the gut of a suitable host, the joint and the egg-shells,
or the latter only, as the case may be, are digested in the stomach or
intestine, so that the larvæ are set free. These (Fig. 137) are
spherical, glass-like, of microscopic size, as might be expected, and
bear three pairs of hooklets, by means of which they quickly perforate
the wall of the gut, and make a way through the tissues of the host.
They may also be carried further by the blood-stream. The larva of a
particular species settles down finally, not only in some particular
kind of host, but also in some definite organ or tissue. It then loses
its hooks, and is rapidly transformed into a hollow _bladder-worm_
(measle), which grows till it reaches a definite size, depending on the
species. Meanwhile it gradually develops one (_Cysticercus_) or several
(_Cœnurus_) ingrowths, or (in _Echinococcus_, Fig. 138) several new
bladders are developed inside the bladder-worm, and ingrowths are
usually formed within these, similar to those of the simpler kinds of
bladder-worm. These ingrowths resemble tapeworm heads in all respects,
possessing suckers, and, it may be, a circlet of hooks, but these are
_inside_, and not _outside_. Later—either in the animal originally
inhabited by the bladder-worm, or after it has been transferred in the
flesh of this to the gut of some carnivorous animal—the bladder-worm
contracts, so that it can no longer hold the fluid which is present, and
the ingrowth is turned inside out, the suckers thus becoming external.
The tapeworm head is formed in this way, but the bladder still remains
attached to its hinder end (Fig. 139). If a host inhabited by
bladder-worms is not devoured by another animal, the bladder-worms,
after reaching their full size, remain for a long time in the same stage
of development without being able to develop further. But if the host is
devoured by another animal, the bladder-worms enter its stomach and
intestine, where the bladder is digested, while the tapeworm head
remains uninjured. This thrusts out its suckers and attaches itself by
means of them to the wall of the intestine, the process of
joint-formation already described beginning soon afterwards.
The following tapeworms, which are important to the owner of stock, will
be briefly dealt with.
The =Common= or =Armed Tapeworm of Man= (_Tænia solium_).
[Illustration:
FIG. 140.—Measles in Pork; the white spot is the head (natural size).
]
Six to ten feet long, with seven to eight hundred joints, and a circlet
of hooks (Fig. 136), lives in the human intestine. Several of its
sexually mature joints are commonly pinched off at a time, and if these
are picked up from a field or dung-heap by a pig, the contained eggs
develop into “pork measles” (_Cysticercus_, Fig. 140), which are
especially abundant in the connective tissue between the muscles, and
make the meat “measly.” They may also occur in the connective tissue of
other parts (fat, brain, spinal cord). Young pigs not more than six
months old are most in danger of becoming measly. A tolerably large
number of measles can be borne very well, but if very abundant they
cause emaciation, weakness, lameness, and poverty of blood. The flesh of
an animal badly infested with measles may be pale, watery, or even
greasy, while pork not so much diseased may seem all right, though it is
really unfit for food, since if eaten in an insufficiently cooked state
by human beings it would produce tapeworms. The measles are most
abundant in the muscles of the breast and neck, and next to them in
those of the hams and shoulders. From twelve to twenty thousand measles
may be present in a single pig.
The =Unarmed Tapeworm of Man= (_Tænia saginata_)
lives in the intestine of man, and, as a bladder-worm (_Cysticercus_),
in the connective tissue of the muscles of the ox (and especially in the
calf). It is from twelve to twenty feet, with as many as a thousand
joints, but does not possess a circlet of hooks. The joints generally
leave the intestine one by one, and creep on to grass and herbs, where
they burst, so that the eggs are set free, and therefore get widely
distributed. The ox scarcely ever takes in several joints of _Tænia
saginata_, and consequently only a certain number of eggs. Beef never,
therefore, contains so many measles as pork, and there is not a special
measle disease of oxen. As, however, the eggs of _Tænia saginata_ are
more widely distributed, calves and oxen are more frequently infected
with bladder-worms than is the case with swine.
The =Cœnurus Tapeworm of the Dog= (_Tænia cœnurus_)
is the cause of the bladder-worm, producing sheep-gid, or sturdy
(_Cœnurus cerebralis_). This tapeworm, which may live in the intestine
of other animals besides the dog, has a circlet of hooks, is from
fourteen to sixteen inches long, and consists of about two hundred
joints. It generally lives in the intestine of the sheep-dog, in
correspondence with which is the fact that the bladder-worm lives in the
brain of young sheep. If a sheep-dog harbours _Tænia cœnurus_ in its
stomach, a sheep may very easily take up a joint with grass or heath.
The joint is then digested in the sheep’s intestine, and the larva
escapes from the egg. It bores through the wall of the sheep’s
intestine, gets into the circulation, and is carried by the blood-stream
to various parts of the body; it can only develop further, however, in
the brain (or spinal cord). After the minute larvæ have reached the
cavity of the cranium they move about on the outer surface of the brain,
and dig out channels there till they find a suitable place for further
growth. The larva now becomes a bladder-worm, which gradually grows,
until it attains a size varying from that of a nut to that of a hen’s
egg. It develops numerous tapeworm heads, even from three to four
hundred. These become tapeworms if a sheep is killed by the parasite,
and its head devoured by a dog or fox.
The disease caused by the presence of bladder-worms in the brain is
called “gid,” or “sturdy,” also “staggers.” Two stages can be
distinguished in it. During the first period the symptoms of disease are
chiefly due to the wounds which the larvæ make on the surface of the
brain, and the consequent inflammation of the investing membranes. Even
in this stage the disease may be fatal, but the symptoms cease as soon
as the larvæ cease to move about. The bladder-worms are only able to do
harm by the pressure they exert, which is small at first, though it
gradually becomes greater. The first stage of gid manifests itself in
late summer, the second in late autumn, winter, or spring, according to
the rate at which the bladder-worms develop. The symptoms of the first
stage are caused by the increased flow of blood to the brain and head
generally, resulting from the irritation which the larvæ exert. (Head
very hot. Eyes bloodshot. The sheep are sluggish but restless, and carry
their heads in a strange way, to one side, bent back, or turned up. They
often run round in a large circle. There may also be gnashing of the
teeth, foaming at the mouth, squinting, convulsive movements, and loss
of consciousness.) The symptoms of the disease in its second stage are
the result of pressure on the brain and some of the arteries of the
brain and skull. (The sheep affected separate themselves from the
others, and generally hang their heads. Gaze fixed. Occasional loss of
consciousness. Movements strange; run or turn round in a circle. The
sheep often staggers and falls to the ground. The bones of the skull
become thinner at the place under which the bladder-worm is found,
sometimes even as thin as paper.)
_Remedies_: Trepanning, as the bladders lie just underneath the roof of
the skull. _Prevention_: Reducing the number of sheep-dogs; giving the
dogs medicine to rid them of tapeworms in spring and summer;
administering a specific to the yearling sheep in July and August,
suitable for driving out any tapeworm larvæ which may be present in
their intestines; _burning_ (instead of _burying_) the heads of sheep
affected with staggers which have died or been slaughtered. It is but
rarely that all the larvæ living on the surface of the brain die between
the first and second stages of the disease. A sheep affected by gid is
therefore almost sure to die, and should be slaughtered as soon as
possible. Compare “false gid,” p. 189.
The =Minute Tapeworm of the Dog= (_Tænia eckinococcus_)
is at most scarcely one-sixth of an inch long, and consists of only
three or four joints, often lives in large numbers in the intestine of
the dog without injuring its host, but causes huge cysts (from the size
of a pigeon’s egg to that of a child’s head) in the liver, lungs, or
other organs of man, pig, and ruminants. These cysts are of the type
represented on the right of Fig. 138. They may prove fatal, owing to the
pressure they exert in the organs containing them and the blood-vessels
of the same.
The =Expanded Tapeworm= (_Tænia expansa_)
lives in the intestine of the ox, where it may attain the length of two
feet, while in the intestine of the lamb it reaches at most the length
of about nineteen inches. It is sometimes present in large numbers in
lambs, causing difficulty of digestion with resulting emaciation,
poverty of blood, and even death. Bladder-worm still unknown.
ORDER: =Trematoda= (FLUKES).
Flattened parasitic worms, tongue-shaped or leaf-shaped, living on or in
a host, and provided with one or two ventral suckers. The intestine
forks into two branches immediately behind the gullet, and these two
divisions in some species (_e.g._ the large liver-fluke) branch again
repeatedly in a tree-like fashion. Anus and blood-vessels absent. Almost
all flukes are hermaphrodite; they fertilize themselves. All the forms
living within a host (_i.e._ endoparasitic forms) lay an immense number
of small eggs, from which larvæ are hatched that become asexually
reproducing animals. These or their progeny produce once more the sexual
form. The development is therefore an example of metagenesis (p. 16),
but there is a change of host. Only the two liver-flukes need be dealt
with here.
The =Large Liver Fluke= (_Distoma hepaticum_),
(Fig. 141), is flat, but swollen in the middle, when it contains a large
number of eggs, under which circumstances the edges only are flat. The
last are of a dirty brown colour, while the middle of the body is
greyish yellow. There is a triangular projection at the front end of the
body with a sucker at the apex, and another at hinder end of the
triangle. The outer surface of the body is covered with minute
backwardly projecting spines, which present no hindrance to the forward
creeping of the body in the bile-ducts, but make backward creeping or
gliding impossible.
[Illustration:
FIG. 141.—The Liver Fluke (_Distoma hepaticum_), natural size.
]
Eggs ¹⁄₁₈₀ of an inch long, with a red shell possessing a greenish
sheen. They can only develop if they get into water, and in wet years
the conditions are very favourable on damp meadows, for under such
conditions the sheep-dung, with the contained fluke eggs, is liable to
fall into pools of water. But many of the eggs can develop in years that
are not so wet and on dryer fields, as they may be carried into a ditch
by rain or on the feet of the sheep. The larva hatched from the egg of
the liver-fluke is ¹⁄₁₂₅ of an inch long, elongated in shape, and swims
about freely in the water by means of a covering of cilia (Fig. 142,
_a_). It soon finds its way into the lung cavity of a small water snail
(_Lymnæus truncatulus_, Fig. 142, _i_), loses its covering of cilia, and
becomes broader, even almost spherical. In the free-swimming larva there
are already to be found a collection of germinal cells in the hinder
part of the body; later on, these cells repeatedly divide and form
little heaps, which ultimately become fresh individuals. The larva has,
therefore, passed into a second stage, and this is now known as a
_sporocyst_ (Fig. 142, _b_, _c_). The stage developed asexually from the
heap of germinal cells is distinguished from the sporocyst by a
differently shaped body and by the possession of a gut (with mouth,
pharynx, and intestine, but no anus), which is absent in the latter.
This stage is termed a “_redia_” (Fig. 142, _d_). From five to eight of
them are usually developed within one sporocyst. Germinal cells are also
present in the redia, and they develop into little heaps of cells from
which, while the weather is warm, new rediæ are developed, that live in
the lung cavity of the snail, like their parents. When the weather
becomes colder, “_cercariæ_” (Fig. 142, _f_) are developed from the
germinal cells, some fifteen to twenty of them within a single redia
(Fig. 142, _e_). The cercaria has a long tail, by means of which it can
propel itself in the water, after leaving the mother redia and the
snail. It possesses two suckers, and a forked intestine without anus.
After the cercariæ have moved about in the water for some time they fix
themselves, by means of their suckers, to various plants growing in the
water. The tail being now superfluous is lost, the cercaria becomes
spherical, and contracts somewhat within an investment which it secretes
(Fig. 142, _g_). When, later on, the pools in which the cercariæ live
dry up, the plants which were before submerged are now on dry land, and
may be devoured by sheep, together with the encysted cercariæ found upon
them. The wall of the cyst is dissolved in the intestine of the sheep,
and the contained cercaria gradually becomes a young liver-fluke, which
at first is oval and very small (Fig. 142, _h_), while, later on, its
anterior third becomes the triangular projection at the front end of the
adult fluke, and its posterior two-thirds grow very considerably.
Meanwhile the young liver-fluke has travelled from the intestine of the
sheep into its bile-ducts. It appears that the fluke is completely grown
within a few weeks after its introduction into the body of the sheep.
Infection almost always takes place in summer or autumn. The life
history of the liver-fluke exemplifies change of host and metagenesis
(p. 16). From the egg of a sexual worm a free-swimming larva is
developed, which becomes an asexual _sporocyst_ within the snail. This
sporocyst produces asexual _rediæ_, and from these, also asexually, are
developed _cercariæ_, which leave the snail, pass into water, attach
themselves to plants, and reach the intestine of the sheep later on. The
cercariæ become flukes by a process of metamorphosis, and are to be
regarded as fluke larvæ.
[Illustration:
FIG. 142.—Liver Fluke: _a_, free-swimming ciliated larva; _b_, young
_Sporocyst_, a few days after migration into the snail; _c_,
_sporocyst_, containing rediæ in various stages of development; _d_,
_redia_, containing balls of germinal cells; _e_, mature _redia_,
containing its brood of cercariæ; _f_, _mature cercaria_; _g_,
just-encysted _cercaria_; _h_, young fluke, soon after entering
sheep; _i_, the water snail, _Lymnæus truncatulus_.
_a_, _b_, _c_, _d_ × 200; _e_ × 150; _f_ × 300; _g_ × 150; _h_ × 25;
_i_, natural size and × 3½.
]
It is easily explained why the “fluke disease,” or “liver rot,” caused
by the fluke should appear much oftener in some regions than others.
Low-lying pastures which are now and then flooded are best suited for
the development of the disease, since the fluke eggs have a better
chance of developing upon them. This is because at certain times of the
year there are in such spots numerous submerged plants on which
_cercariæ_ encyst, and which, later on, when the pools dry up, are
nibbled by sheep. It seems that the _cercariæ_ mostly attach themselves
to certain kinds of plants, hence the local nature of the disease, which
of course also depends on the presence of _Lymnæus truncatulus_ (Fig.
142, _i_).
Fluke disease first makes itself apparent in the sheep one or two months
after infection. If the sheep does not die the parasites often remain in
its liver till the next spring. The liver of a single sheep may contain
from 200 to 250 individuals. They live in the various branches of the
bile-duct, and the irritation they set up first causes an unusual
quantity of blood to flow to the liver. Inflammation and internal
bleeding may result, and gall stones are deposited in the thickened
walls of the biliary passages. The flow of bile from the liver is made
difficult or impossible. Later on, the parasites draw so much blood from
the liver that this organ is very insufficiently nourished, so that no
more bile is secreted, and the liver substance shrivels up. In
consequence of these changes the digestion is incomplete, and the whole
body of the sheep is very insufficiently nourished. The diseased sheep
are therefore sluggish and enfeebled; they eat little, but drink a great
deal, and suffer from poverty of blood. Their wool gets dry, and does
not hold together, and they become emaciated. Dropsy and diarrhœa set
in, and jaundice often makes its appearance. If a sheep is infested by a
tolerably large number of flukes, death is almost always the final
result.
“The best _preventative_ is a trustworthy and careful shepherd,”[5] who
will not let the sheep feed in spots where previous experience shows the
disease is usually contracted during damp summers. Furthermore, sheep
badly infested should be slaughtered as soon as possible, so that the
flukes they contain may not get to the egg-laying stage. Sick sheep
should be fed with nourishing food (various kinds of hay, oats; with
addition of cooking salt), so that young sheep containing but few flukes
may get back their strength, while this treatment will make the badly
infested sheep die more quickly.
Footnote 5:
Spinola.
Oxen are also frequently affected by fluke disease in many regions,
other animals to a less extent.
The =Small= or =Lancet-shaped Liver Fluke= (_Distoma lanceolatum_)
is about three-eighths of an inch long, one-tenth of an inch broad,
thin, and lancet-shaped. Lives, like the preceding kind, in the liver of
the sheep. Development unknown.
=Fourth Sub-Kingdom: MOLLUSCA= (MOLLUSCS).
This sub-kingdom, to which oysters, snails, cuttle-fish, etc., belong,
includes unsegmented animals devoid of internal skeleton, and with
bilaterally symmetrical (p. 16) embryo, while the adult may be much
modified, especially in snails, which are enclosed in spiral shells, and
also have their bodies partially coiled. The skin of molluscs possesses
a peculiar and characteristic covering. From a definite part of the body
a larger or smaller fold of skin (“mantle”) grows out, which encloses a
space termed the “mantle-cavity,” and also, from its function, the
“respiratory cavity.” In most molluscs this mantle secretes an external
or internal calcareous mass. In this way a “shell” is developed (Fig.
143, A, _S_), which is usually external. This is the case, for example,
with the edible, or Roman snail, and the common garden snail. In other
cases (cuttlefishes), the shell is formed inside the mantle, or it may
be replaced by a collection of calcareous granules (various slugs). In
most molluscs the chief organ of locomotion is the so-called “foot”
(Fig. 143, _F_). This is a very muscular region of the body, covered by
skin, and serving either for crawling (snails), or else for digging in
the sand, and even springing (bivalve molluscs). Its structure varies
according to its function. I mention three classes, those of
_Cephalopoda_ (Cuttlefishes), _Gastropoda_ (Snails and Slugs), and
_Lamellibranchiata_ (Bivalve Molluscs).
[Illustration:
FIG. 143.—Diagrams to explain the form of the body of a Mollusc. A, a
Bivalve Mollusc; B, a Snail (cross sections). In both; _K_, body;
_F_, foot; _S_, shell; _m_, mantle; _k_, _k_, gills.
]
CLASS: =CEPHALOPODA= (CUTTLEFISHES).
The head is sharply marked off from the rest of the body, and the mouth
is surrounded by a circle of arms bearing suckers or claw-like hooks.
These arms are supposed to be a modification of part of the foot, the
rest of this organ being constituted by a hollow, funnel-shaped
structure, which places the mantle-cavity in communication with the
exterior. The water used for respiration is forced suddenly out from the
mantle-cavity, through the funnel, so as to propel the animal in the
opposite direction. A gland, known as the “ink sac,” secretes a brownish
fluid, which may be pressed out of the sac so as to shield the animal
from attack. All cephalopods are marine, and, since they are therefore
of no agricultural importance, it is unnecessary to enter into details
regarding their form and structure, and I will only mention the
following: =Pearly Nautilus= (_Nautilus pompilius_), with external shell
and numerous arms; =Paper Nautilus= (_Argonauta argo_), with a very
thin, boat-shaped shell, and eight arms; =Poulpe= (_Octopus_), without
shell, and with eight arms; =Cuttle-fish= (_Sepia_), and =Squid=
(_Loligo_), also without external shell, and possessing ten arms.
CLASS: =GASTROPODA= (SNAILS AND SLUGS).
Snails and slugs possess a head which bears unjointed tentacles, and
also eyes, which, in many cases, are borne on the tips of these. The
foot serves for creeping, and is flattened in a sole-like way on its
under side. The mantle is generally small, and limited to the dorsal
side of the animal. The usually spiral shell covers therefore only a
small part of the body, but the rest of the body can also be mostly or
entirely drawn back into it. Snails possess jaws, but the chief organ
used in attacking the plant structures is the swollen tongue, covered by
a rasping plate (radula), on the surface of which regular rows of teeth
are arranged. The rest of the tongue consists of muscle, and two small
cartilages are also found within it. The teeth stick up when the tongue
is protruded, and the whole apparatus forms a kind of rasp, by the
backward and forward movements of which the food is reduced to small
fragments. Marine snails breathe by gills, which are found in the
mantle-cavity, while most of the freshwater and all the land forms
(“Pulmonata”) breathe by means of the inner wall of the mantle-cavity,
which thus serves as a lung. Some members of the group are
hermaphrodite, while the sexes are distinct in others; the first is the
case in all terrestrial forms. Such snails pair, however, mutually
fertilizing each other. They are not able to fertilize themselves. It is
only among land snails and slugs that injurious kinds are found. Species
of the genus _Helix_, _e.g._ the =Edible= or =Roman Snail= (_H.
pomatia_) and the =Field Snail= (_H. nemoralis_), may do harm in
fruit-culture; =Slugs= are very injurious to agriculture (_Limax_ and
_Arion_); in Limax, the respiratory opening is situated behind the
middle of the right margin of the mantle, while the genital opening lies
behind the right feeler; in Arion, the respiratory opening is situated
on the front edge of the mantle, and the genital opening immediately in
front of it. Any kind of snail or slug may be harmful, especially if it
attacks young plants. Some kinds, however, live chiefly in woods,
feeding upon toadstools and dung, perhaps also on bark and weeds (_e.g._
dandelion). This is especially true of the larger kinds, but these too,
if they multiply very rapidly, may effect much damage in gardens and
fields. The commonest slugs are—
The =Common Black Slug= (_Arion ater_).—About four inches long, and
generally black.
The =Grey Field Slug= (_Limax agrestis_, Fig. 144).—Four-fifths of an
inch long, small and smooth, with dark tentacles, grey back, often a
reddish sheen, and bright grey or white under side.
The =Large Slug= (_Limax maximus_).—Up to six inches long, with black
flecks on the hump-like mantle, and black streaks on the rest of the
body.
In a large majority of cases where slugs appear to an injurious extent,
the grey field slug is the offender, and I will therefore deal with it
in greater detail. What is said regarding the small species, however,
may be taken to apply to all the other kinds, should they become a pest.
The =Grey Field Slug= (_Limax agrestis_).
[Illustration:
FIG. 144.—The Grey Field Slug (_Limax agrestis_).
]
The life of the grey field slug is very dependent on moisture. During
dry weather it rolls itself up and hides in the ground, under a stone,
or in some such place, where it is protected as much as possible from
completely drying up. At such times it only comes to the surface to feed
at night, but does so during the day as well when the weather is wet.
The field slug is very destructive in fields and gardens, but this is
only the case in those years the great dampness of which is specially
favourable to its continuance and multiplication. The glassy eggs are
laid in heaps containing from six to fifteen, in damp concealed spots in
the ground, under moss, grass, etc., during August, September, and even
October. A single slug may lay as many as four hundred. The eggs are
able to withstand extreme cold and extreme dryness, and moisture makes
them swell out again if they have shrivelled up. In warm, damp weather
the young slugs (which are one-twelfth of an inch long in the
contracted, and two-fifths of an inch in the extended condition) hatch
out in three or four weeks. Cold weather retards the development. If the
weather is favourable, and suitable food is not wanting, they are often
almost full-grown in six weeks’ time. It is clear, from the foregoing,
that in damp years the slugs may appear in very large numbers,
especially in autumn; but it may also happen that most of the young
slugs hatch out the following spring, in which case the greatest amount
of damage will be done then. A snail may live several years, spending
the dry days and the whole of the cold season in the ground or some
other sheltered place. These slugs devour by preference delicate leaves
and stems; young grain, young clover plants, leaves of rape, cabbage,
turnips, and lettuce are their favourite food, also fallen fruit,
strawberries, cucumbers, and vegetable marrows. _Preventive Measures_:
Protection of their natural enemies: pigs, moles, shrews, ducks, fowls,
pigeons, rooks, starlings, toads. Draining the soil, as slugs flourish
most where it is moist. Sowing the winter grain as soon as possible, as
the young plants will then probably have attained a fair size when the
slugs appear in force. _Remedies_: Collection. The slugs readily crawl
on to bits of cucumber or turnip which are thrown down, and can then
easily be collected, or killed with quicklime. All substances which
readily absorb water kill slugs by taking from them the moisture which
is necessary for their existence. Cooking-salt, unslaked and slaked lime
may be employed for this purpose. It seems to me most convenient to use
freshly slaked lime, ten to twelve bushels per acre. Since the lime can
only kill the slugs when it comes into contact with their skins, it must
always be strewn on the land at a time when they are on the crawl, not
later than 8 a.m., and only in dry weather. As soon as the slugs are
touched by the lime they begin to give out a great deal of slime, and
many of them, especially the younger ones, are killed and become black.
Very many of the older slugs, however, escape death, since the tenacious
slime they give out, when the lime touches them, forms a continuous coat
like a cocoon, out of which the slug creeps, now much poorer in water.
It is therefore a good plan to strew powdered lime over a slug-infested
field twice in succession, leaving an interval of some ten or fifteen
minutes. The second strewing brings the lime into contact with those
slugs which have just crawled out of their slimy investment in a
desiccated condition. They are unable to form a second coating of slime,
and if touched for this second time with even the smallest particles of
lime they at once contract and die. If a double strewing is repeated
very early on the following morning, no slugs will be left alive on the
field so treated.
CLASS: =LAMELLIBRANCHIATA= (BIVALVE MOLLUSCS).
Headless. The mantle consists of two flaps, which secrete two shelly
pieces (valves) movably united on the dorsal side (Fig. 43). The foot is
usually wedge-shaped. Respiration effected by gills placed in the
mantle-cavity, which communicates with the exterior either by the usual
respiratory opening, or by a breathing-tube (siphon). Most species are
marine, but some live in fresh water. No kind is of agricultural
importance. To this class belong the =Oyster= (_Ostrea edulis_), the
=Sea Mussel= (_Mytilus edulis_), the tropical =Pearl Mussel=
(_Meleagrina margaritifera_), the freshwater =Swan Mussel= (_Anodonta
cygnea_), the notorious =Ship Worm= (_Teredo navalis_), etc.
=Fifth Sub-Kingdom=: =ECHINODERMATA= (HEDGEHOG-SKINNED ANIMALS).
[Illustration:
FIG. 145.—The Common Starfish (_Asterias rubens_), seen on the right
from above, on the left from below.
]
The echinoderms are radially symmetrical, i.e. a number of similar parts
which together make up the body are arranged around an axis (Fig. 145).
These animals are usually five-rayed. The mouth lies at lower end of the
axis of the body. In some echinoderms the radial symmetry is indistinct,
and at the same time there is a more or less clear bilateral symmetry
(p. 16). The dermal skeleton either consists of numerous microscopic
calcareous deposits, or of firm plates; the skin often bears spines,
hence the name of the group. Echinoderms move by means of rows of
tubular feet, which are connected with a water-vascular system, and are
protruded by means of small bladders, connected with the same system,
which contract and force water into them. The form of the body is
apple-shaped to spherical (=Regular Sea Urchins=), shield- or
heart-shaped (=Irregular Sea Urchins=), pentagonal to star-shaped, with
arms of varying length (=Starfishes=), or cylindrical to vermiform (=Sea
Cucumbers=). All echinoderms are marine, and none of them, therefore,
are of agricultural importance, though near the coast starfishes are
sometimes used as manure.
=Sixth Sub-Kingdom=: =CŒLENTERATA= (ZOOPHYTES).
With a few exceptions the zoophytes are radially symmetrical (p. 252),
and four-, six-, eight-, or many-rayed. They consist of a body-wall
enclosing a cavity which, in the simplest forms (Fig. 146), is
sack-like, but in several of the higher sub-groups divided up, and
serves, not only for the reception and digestion of food, but also for
the circulation of the digested food. Many zoophytes develop hard parts
in the walls of their bodies, which remain after their death. The red
coral used for ornamental purposes is of this nature, and so also are
the coral islands which polypes build up. With the exception of the
sponges, which are usually reckoned as belonging to this sub-kingdom,
these animals possess “nettling organs” with which they kill their prey,
and by which they are protected from attack. They reproduce by eggs, and
most of them by means of budding as well (Fig. 146). In many species the
buds are not detached as in the Freshwater Polype (_Hydra_), but remain
attached so that a “colony” is formed. There are also free-swimming
cœlenterates, known as jellyfishes or medusæ (Fig. 147). Many of these
lay eggs which do not develop into fresh medusæ, but into polypes, which
increase by budding to form colonies, on which medusæ are once more
developed as buds. There is thus an _alternation of generations_ (p.
16), in which the medusæ represent the _sexual_ and the polypes the
_asexual_ stage.
[Illustration:
FIG. 146.—Freshwater Polype (_Hydra_), bearing two buds of different
ages. Highly magnified.
]
[Illustration:
FIG. 147.—A Phosphorescent Jellyfish (_Pelagia noctiluca_), ½ the
natural size.
]
[Illustration:
FIG. 148.—A Sea Anemone (_Sagartia nivea_).
]
Almost all zoophytes live in the sea, but some few in fresh water; none
are important agriculturally. The following belong to this sub-kingdom:
1. The =Hydroid Zoophytes= (_Hydrozoa_), including the medusæ of the
North Sea, many of which are the sexual stage in the life history of
fixed asexual polypes. The common =Freshwater Polypes= (_Hydra viridis_,
_fusca_, etc.). 2. The =Flower Polypes= (_Anthozoa_), to which belong
=Red Coral= (_Corallium rubrum_), and the =reef-building corals=
(_Astræa_, _Mæandrina_, etc.). 3. The =Sponges= (_Porifera_), which are
usually considered cœlenterates, though they possess no nettling organs
(=Freshwater Sponge= = _Spongilla_, =Bath Sponge= = _Euspongia
officinalis_).
=Seventh Sub-Kingdom: PROTOZOA= (ONE-CELLED ANIMALS).
[Illustration:
FIG. 149.—Two species of Proteus Animalcule (_Amœba_), one with
protoplasmic processes, slender and branched; the other with short
blunt processes. Highly magnified.
]
This sub-kingdom includes animals which are mostly microscopic, or at
any rate small, and live in the sea, fresh water, or damp places. They
are unicellular, and consist of a soft viscous substance (_protoplasm_
or _sarcode_) of contractile nature, and therefore capable of altering
its shape. They may or may not be enclosed by a firm wall. Many secrete
siliceous structures or calcareous shells. They are of no agricultural
importance. Here belong: =Infusoria=, common in putrid solutions; and
=Rhizopods=, such as _Amœba_, the =Proteus Animalcule= (Fig. 149), so
called because its shape is constantly altering.
THE END.
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