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Transcriber's note:
In this Plain Text version of the book only symbols from the
ASCII character set have been used.
Text in italic typeface is enclosed by underscores (_italics)_.
Text in small capital typeface is displayed as ALL UPPER CASE.
Text in bold typeface is enclosed by equal symbols (=bold=).
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Instances of distinctive font symbols (T, V, W, Y) which occur
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Note that numerous taxonomic names have changed since 1894.
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BUTTERFLIES AND MOTHS
(British)
* * * * *
OUT-DOOR WORLD LIBRARY.
THE OUT-DOOR WORLD; or, Young Collector's Handbook. By W. FURNEAUX,
F.R.G.S. With 18 Plates, 16 of which are coloured, and 549
Illustrations in the Text. Crown 8vo. 7_s._ 6_d._
BUTTERFLIES AND MOTHS (BRITISH). By W. FURNEAUX, F.R.G.S. With 12
coloured Plates and 241 Illustrations in the Text. 10_s._ 6_d._ net.
_To be followed by_
BRITISH BIRDS. By W. H. HUDSON, F.Z.S. With a Chapter on Structure
and Classification by FRANK E. BEDDARD, F.R.S.
LIFE IN PONDS AND STREAMS. By W. FURNEAUX, F.R.G.S.
BRITISH MAMMALS AND REPTILES.
AND OTHER VOLUMES.
London: LONGMANS, GREEN, & CO.
New York: 15 East 16th Street.
[Illustration: Plate I
_Danielsson & Co., del. ad. Nat. et Chromolith._]
* * * * *
BUTTERFLIES AND MOTHS
(British)
by
W. FURNEAUX, F.R.G.S.
Author of 'The Out-Door World, Or Young Collector's Handbook'
[Illustration]
With Twelve Coloured Plates and Numerous Illustrations in the Text
London
Longmans, Green, and Co.
And New York. 15 East 16th Street
1894
All rights reserved
PREFACE
The favourable reception with which the 'Out-door World' has been
greeted has encouraged the publishers to issue a series of volumes
dealing in fuller detail with the various branches of Natural History
treated of in that work. Necessarily each subject was only briefly
touched upon, but the study is of so enticing a character that 'appetite
grows by feeding,' and the students of the 'Out-door World,' having
tasted the sweetness of companionship with Nature, will not rest
satisfied with the help afforded by that handbook. Each one will want to
go deeper into that particular department which most appeals to his own
inclinations.
The present volume is written expressly for those who desire to extend
their knowledge of the British Lepidoptera, or, to use the more popular
names, 'Butterflies and Moths.'
The general characteristics of this interesting order of insects are
described somewhat fully, but, of course, it would be impossible to give
an individual account of all the British Lepidoptera in a work of this
size, so a selection has been made such as will satisfy the requirements
of the great majority of those who intend to take up this particular
branch of entomology. The number of British Butterflies, however, is
so limited that a place has been found for a figure and a description of
every species; and, of the larger moths, many of the common and typical
kinds have been included. An introduction to the study of the
Micro-lepidoptera has also been added.
No trouble has been spared to render this work thoroughly practical. In
addition to the verbal descriptions of so many species, twelve coloured
plates and a large number of woodcuts have been specially prepared to
help the student in his work. It is believed that the extreme care with
which these have been produced will render them of the greatest
assistance to the collector in the recognition of his specimens.
But he has not only to recognise his specimens--he must first catch
them; and here full directions have been given to insure success in this
part of his work, as well as in the management, preservation, and
arrangement of his captures.
The Author hopes that this volume may be the means of adding many happy
hours--hours of the purest enjoyment--to the lives of those whom he has
succeeded in luring into the fields and lanes and woods of the Out-door
World.
CONTENTS
PART I
_STRUCTURE AND LIFE HISTORY OF THE LEPIDOPTERA_
CHAP. PAGE
I. GENERAL CHARACTERS 1
II. THE EGG 16
III. THE LARVA 22
IV. THE PUPA OR CHRYSALIS 40
V. CLASSIFICATION OF THE LEPIDOPTERA 55
PART II
_WORK AT HOME AND IN THE FIELD_
VI. CATCHING BUTTERFLIES AND MOTHS 63
VII. COLLECTING OVA, LARVAE, AND PUPAE 98
VIII. REARING LEPIDOPTERA 112
IX. SETTING AND PRESERVING 122
X. PRESERVING OVA, LARVAE AND PUPAE 130
XI. THE CABINET--ARRANGEMENT OF SPECIMENS 134
PART III
_BRITISH BUTTERFLIES_
XII. THE SWALLOW-TAIL AND THE 'WHITES' 139
XIII. THE FRITILLARIES, VANESSAS, AND THE PURPLE EMPEROR 154
XIV. THE BROWNS AND HEATHS 173
XV. THE HAIRSTREAKS, COPPERS AND BLUES 183
XVI. THE DUKE OF BURGUNDY AND THE SKIPPERS 196
PART IV
_COMMON BRITISH MOTHS_
XVII. SPHINGES 203
XVIII. BOMBYCES 217
XIX. THE NOCTUAE 239
XX. GEOMETRAE 268
XXI. THE MICRO-LEPIDOPTERA 290
APPENDICES
I. COMPLETE CLASSIFIED LIST OF BRITISH MACRO-LEPIDOPTERA 309
II. THE LEPIDOPTERIST'S CALENDAR 326
REFERENCES TO COLOURED PLATES 347
INDEX 351
LIST OF ILLUSTRATIONS
_COLOURED PLATES_
1-7. BRITISH BUTTERFLIES _Frontispiece_
8. LARVAE AND PUPAE OF BRITISH BUTTERFLIES }
9. SPHINGES }
10. BOMBYCES } _At end_
11. NOCTUAE }
12. NOCTUA AND GEOMETRAE }
_Full references accompany the Plates._
_ILLUSTRATIONS IN THE TEXT_
FIG. PAGE
1. SCALES FROM THE WINGS OF BUTTERFLIES 1
2. PORTION OF THE WING OF A BUTTERFLY FROM WHICH SOME OF THE
SCALES HAVE BEEN REMOVED 2
3. BODY OF A BUTTERFLY--UNDER SIDE 3
4. SECTION OF THE EYE OF AN INSECT 4
5. ANTENNAE OF BUTTERFLIES 5
6. ANTENNAE OF MOTHS 5
7. SECTION OF THE PROBOSCIS OF A BUTTERFLY 7
8. DIAGRAM OF THE WINGS OF A BUTTERFLY 9
9. THE UNDEVELOPED FORE LEG OF A BUTTERFLY 10
10. THE FOUR STAGES OF THE LARGE WHITE BUTTERFLY
(_Pieris Brassicae_) 14
11. EGG OF THE MEADOW BROWN BUTTERFLY 20
12. EGG OF THE SPECKLED WOOD BUTTERFLY 20
13. EGG OF THE VAPOURER MOTH 20
14. THE CATERPILLAR OF THE CLOUDED YELLOW BUTTERFLY 22
15. THE CATERPILLAR OF THE DARK GREEN FRITILLARY BUTTERFLY 23
16. THE CATERPILLAR OF THE PURPLE EMPEROR BUTTERFLY 24
17. AN ICHNEUMON FLY (_Cryptus Migrator_) 25
18. ANOTHER ICHNEUMON FLY (_Pimpla Instigator_) 25
19. THE CATERPILLAR OF THE ANGLE SHADES MOTH (_Meticulosa_) 26
20. WALKING LEG OF A CATERPILLAR 28
21. LARVA OF THE YELLOW UNDERWING MOTH (_Pronuba_) 28
22. LARVA OF THE CRIMSON SPECKLED MOTH (_Pulchella_) 28
23. LARVA OF THE LOBSTER MOTH (_Fagi_) 28
24. CATERPILLAR OF THE IRON PROMINENT MOTH (_Dromedarius_) 29
25. LARVA OF THE BRIMSTONE MOTH (_Luteolata_) 29
26. THE CLASPERS OF A CATERPILLAR 30
27. THE HOMES OF LEAF MINERS AND LEAF ROLLERS 33
28. THE COCOON OF THE EMPEROR MOTH 40
29. THE COCOON OF THE SIX-SPOTTED BURNET (_Filipendulae_) 40
30. THE PUPA OF THE PRIVET HAWK (_Ligustri_) 44
31. THE CHRYSALIS OF THE LARGE WHITE BUTTERFLY (_Brassicae_) 44
32. THE PUPA OF THE DARK GREEN FRITILLARY (_Aglaia_) 45
33. THE PUPA OF THE BLACK-VEINED WHITE BUTTERFLY (_Crataegi_) 45
34. THE PUPA OF THE CURRANT MOTH 45
35. PUPA OF THE PALE TUSSOCK MOTH (_Pudibunda_) 45
36. A BUTTERFLY, JUST AFTER EMERGING 50
37. A BUTTERFLY AT REST (LARGE COPPER) 57
38. A MOTH AT REST (GOTHIC) 57
39. A WIRE FRAME FOR A BUTTERFLY NET 65
40. STICK FOR THE NET 65
41. THE METAL Y 66
42. PATTERN FOR THE NET 67
43. THE CYANIDE BOTTLE 68
44. SECTION OF THE LAUREL BOX 70
45. THE CHLOROFORM BOTTLE 72
46. }
47. } FITTINGS FOR THE COLLECTING BOX 75
48. }
49. }
50. FRAME OF NET FOR COLLECTING INSECTS ON LAMPS AND WINDOWS 87
51. A TRAP FOR CATCHING MOTHS 88
52. METAL JOINT FOR LANTERN AND NET 91
53. NET AND LANTERN FOR TAKING MOTHS FROM HIGH BLOSSOMS 91
54. FRAME FOR THE SUGARING NET 94
55. CAGE FOR DECOY FEMALES 96
56. A SUGAR TRAP 96
57. A LARVA GLASS 114
58. A LARVA GLASS 114
59. A LARVA CAGE 115
60. SECTION OF A SETTING BOARD 123
61. SECTIONS OF SETTING BOARDS 123
62. A BUTTERFLY ON THE SETTING BOARD 124
63. ANOTHER METHOD OF SETTING BUTTERFLIES AND MOTHS 126
64. A BLOWPIPE FOR LARVAE 131
65. THE BATH WHITE--UNDER SIDE 147
66. THE CLOUDED YELLOW--FEMALE 151
67. THE SMALL PEARL-BORDERED FRITILLARY--UNDER SIDE 155
68. THE PEARL-BORDERED FRITILLARY--UNDER SIDE 156
69. THE QUEEN OF SPAIN FRITILLARY--UNDER SIDE 157
70. THE DARK-GREEN FRITILLARY--UNDER SIDE 158
71. THE HIGH-BROWN FRITILLARY 159
72. THE SILVER-WASHED FRITILLARY--UNDER SIDE 160
73. THE GREASY FRITILLARY--UNDER SIDE 161
74. The GLANVILLE FRITILLARY--UNDER SIDE 162
75. THE COMMA--UNDER SIDE 164
76. THE PURPLE EMPEROR--UNDER SIDE 172
77. THE MARBLED WHITE--UNDER SIDE 174
78. THE WOOD ARGUS--UNDER SIDE 176
79. THE GRAYLING--UNDER SIDE 178
80. THE LARGE HEATH--UNDER SIDE 179
81. THE RINGLET--UPPER SIDE 180
82. THE MARSH RINGLET--UNDER SIDE 181
83. THE BROWN HAIRSTREAK--MALE 184
84. THE WHITE-LETTER HAIRSTREAK 184
85. THE PURPLE HAIRSTREAK--MALE 186
86. THE GREEN HAIRSTREAK 186
87. THE TAILED BLUE--UNDER SIDE 188
88. THE SILVER-STUDDED BLUE--UNDER SIDE 189
89. THE COMMON BLUE--UNDER SIDE 191
90. THE CLIFDEN BLUE--UNDER SIDE 191
91. THE CHALK-HILL BLUE--UNDER SIDE 192
92. THE HOLLY BLUE--UNDER SIDE 193
93. THE MAZARINE BLUE--UNDER SIDE 194
94. THE SMALL BLUE--UNDER SIDE 194
95. THE LARGE BLUE--UNDER SIDE 195
96. THE SILVER-SPOTTED SKIPPER--UNDER SIDE 201
97. THE DEATH'S-HEAD HAWK MOTH 205
98. THE LARVA OF ATROPOS 206
99. THE CATERPILLAR OF EUPHORBIAE 207
100. THE SMALL ELEPHANT HAWK MOTH 208
101. THE POPLAR HAWK 209
102. THE BROAD-BORDERED BEE HAWK 212
103. THE HORNET CLEARWING OF THE POPLAR 213
104. THE CURRANT CLEARWING 213
105. THE FORESTER 214
106. THE SIX-SPOTTED BURNET 215
107. THE LARVA OF FILIPENDULAE 215
108. THE GREEN SILVER-LINED 217
109. THE SHORT-CLOAKED MOTH 218
110. THE MUSLIN MOTH 218
111. THE COMMON FOOTMAN 219
112. THE LARVA OF JACOBAEAE 219
113. THE SCARLET TIGER 220
114. THE BUFF ERMINE 222
115. THE WHITE ERMINE 222
116. THE GHOST SWIFT--FEMALE 223
117. THE COMMON SWIFT 224
118. THE GOAT MOTH 225
119. THE LARVA OF LIGNIPERDA (LESS THAN HALF FULL SIZE) 225
120. THE LEOPARD MOTH 226
121. THE LARVA OF PYRINA (ONLY PARTLY GROWN) 226
122. THE BROWN TAIL 227
123. THE GIPSY--MALE 227
124. THE BLACK ARCHES--MALE 228
125. THE VAPOURER MOTH--MALE 228
126. THE FEMALE VAPOURER 228
127. LARVA OF THE VAPOURER MOTH 229
128. THE DRINKER--MALE 230
129. THE OAK HOOK TIP 233
130. THE CHINESE CHARACTER 233
131. THE POPLAR KITTEN 234
132. THE PUSS MOTH 235
133. THE COXCOMB PROMINENT 235
134. THE LARVA OF BUCEPHALA 236
135. THE CHOCOLATE TIP 237
136. THE PEACH BLOSSOM 237
137. THE YELLOW HORNED 238
138. THE MARBLED BEAUTY 240
139. THE GREY DAGGER 240
140. THE POPLAR GREY 241
141. THE FIGURE OF EIGHT 241
142. THE BROWN-LINE BRIGHT-EYE 242
143. THE SMOKY WAINSCOT 243
144. THE COMMON WAINSCOT 243
145. THE BULLRUSH 244
146. THE FROSTED ORANGE 245
147. THE FLAME 245
148. THE LIGHT ARCHES 246
149. THE FLOUNCED RUSTIC 246
150. THE CABBAGE MOTH 247
151. THE DOT 247
152. THE RUSTIC SHOULDER-KNOT 248
153. THE MARBLED MINOR 248
154. THE MOTTLED RUSTIC 249
155. THE TURNIP MOTH 250
156. THE HEART AND DART 251
157. THE GARDEN DART 251
158. THE FLAME SHOULDER 252
159. THE LESSER BROAD BORDER 252
160. THE LESSER YELLOW UNDERWING 253
161. THE GOTHIC 254
162. THE OLD LADY 254
163. THE COMMON QUAKER 255
164. THE CHESTNUT 256
165. THE PINK-BARRED SALLOW 256
166. THE DUN-BAR 257
167. THE BROAD-BARRED WHITE 257
168. THE ANGLE SHADES 258
169. THE GREY ARCHES 259
170. THE SHEARS 260
171. THE BRIGHT-LINE BROWN-EYE 260
172. THE EARLY GREY 261
173. THE SHARK 262
174. THE BURNISHED BRASS 263
175. THE SILVER Y 264
176. THE RED UNDERWING 266
177. THE LIGHT EMERALD 270
178. THE AUGUST THORN 271
179. THE PEPPERED MOTH 272
180. THE WILLOW BEAUTY 273
181. THE LARGE EMERALD 274
182. THE COMMON EMERALD 274
183. THE LACE BORDER 275
184. THE RIBAND WAVE 276
185. THE BLOOD-VEIN 276
186. THE COMMON WAVE 277
187. THE CLOUDED SILVER 277
188. THE V MOTH 278
189. THE COMMON HEATH 279
190. THE BORDERED WHITE--MALE 279
191. THE CURRANT MOTH 280
192. THE SPRING USHER 281
193. THE MARCH MOTH 282
194. THE NOVEMBER MOTH 282
195. THE TWIN-SPOT CARPET 283
196. THE GRASS RIVULET 283
197. THE NETTED PUG 284
198. THE NARROW-WINGED PUG 284
199. THE BRINDLED PUG 284
200. THE SMALL SERAPHIM 285
201. THE BLUE-BORDERED CARPET 285
202. THE BEAUTIFUL CARPET 286
203. THE COMMON CARPET 286
204. THE SILVER GROUND CARPET 287
205. THE GARDEN CARPET 287
206. THE YELLOW SHELL 288
207. THE SMALL PH[OE]NIX 288
208. THE SMALL MALLOW 289
209. THE TABBY OR GREASE MOTH 291
210. THE MEAL MOTH 292
211. THE SMALL MAGPIE 292
212. THE MOTHER-OF-PEARL 293
213. THE GARDEN PEBBLE 293
214. THE BEAUTIFUL CHINA MARK 294
215. GONODACTYLA 295
216. OSTEODACTYLUS 295
217. PENTADACTYLA 295
218. HEXADACTYLA--ENLARGED 296
219. PHRAGMITELLUS--ENLARGED ONE-HALF 297
220. HAMELLUS--SLIGHTLY ENLARGED 297
221. TRISTELLUS 297
222. HORTUELLUS 298
223. MELLONELLA 298
224. XYLOSTEANA WITH WINGS CLOSED 299
225. VIRIDANA 300
226. CRISTANA--ENLARGED 300
227. LECHEANA 300
228. PRUNIANA 300
229. SALICELLA 301
230. OCTOMACULANA--ENLARGED 301
231. CIRSIANA--ENLARGED 302
232. POMONELLA 302
233. ZOEGANA--ENLARGED 302
234. FAGELLA 303
235. CUPRELLA 304
236. PADELLUS 304
237. NERVOSA--TWICE NATURAL SIZE 304
238. GEOFFRELLA 305
239. IBIPENNELLA--ENLARGED 305
240. COMPLANELLA--ENLARGED 306
241. AURELLA--ENLARGED 307
PART I
STRUCTURE AND LIFE-HISTORY OF THE LEPIDOPTERA
CHAPTER I
_GENERAL CHARACTERS_
The word _Lepidoptera_, which you see at the head of this page, is the
name of the order of insects to which this volume is to be devoted. It
is formed from two Greek words, one (_lepis_) signifying a _scale_, and
the other (_pteron_) denoting a _wing_; and was applied by the great
naturalist Linnaeus to the scaly-winged insects popularly known as
Butterflies and Moths.
[Illustration: FIG. 1.--SCALES FROM THE WINGS OF BUTTERFLIES.]
Every one of my readers has undoubtedly handled some of the interesting
creatures of this group--having been led to do so either by the extreme
beauty of their clothing, or, perhaps, from a murderous intent in order
to protect his own garments from the ravages of a supposed marauder. A
light mealy powder will probably have been observed afterwards on the
fingers that have touched the victim's wings.
This powder, although it sometimes presents a beautiful glossy surface
when spread over the skin, does not exhibit any definite form or
structure without a more minute examination. Yet these are the scales
that led the immortal naturalist to invent the somewhat long but useful
term _Lepidoptera_.
The very next time the opportunity offers itself, dust off a little of
the mealy powder with a small and very soft brush on to a strip of white
paper or a slip of glass, and examine it with a powerful lens or the low
power of a compound microscope. What a sight you will then behold! Each
little particle of dust is a beautifully formed scale, stamped with a
number of minute rounded projections, and often displaying the most
gorgeous colours. A great variety of designs and tints are often
exhibited by the 'dust' from a single wing. Take, for instance, for your
inspection, scales from the wing of one of our commonest insects, the
Small Tortoiseshell Butterfly (Plate III), and you will be surprised at
the pleasing contrasts. But when your curiosity leads you to deal with
others in the same manner, the varied display of forms and colours is
simply amazing.
[Illustration: FIG. 2.--PORTION OF THE WING OF A BUTTERFLY FROM WHICH
SOME OF THE SCALES HAVE BEEN REMOVED.]
In order that we may learn still more of the structure of the wings of
the _Lepidoptera_, we will examine a portion of one from which some of
the scales have been removed, again bringing the lens or the microscope
into our service. We now see that the scales are arranged in rows with
great regularity on a thin and transparent membrane, which is supported
by a system of branching rays. And the membrane itself, in parts which
have been laid bare, is marked with regular rows of dots--the points at
which the scales were originally attached by means of short hollow rods.
The framework that supports the thin membrane we have spoken of as
consisting of a system of _rays_, but to these the terms _veins_,
_nerves_, _nervures_, or _nervules_ are more commonly applied by various
naturalists. We cannot do better, however, than adhere to the name
originally used, for the structures in question do not perform the
functions of veins, though at first they contain blood, nor are they
themselves parts of the nervous systems of the insects to which they
belong.
The result of our examination of the wings of butterflies and moths has
been to justify the application of the term _Lepidoptera_; but we must
now study other equally important and interesting features of the
structure of these insects. First, let us note the general form of the
body.
[Illustration: FIG. 3.--BODY OF A BUTTERFLY--UNDER SIDE.
1-7, segments of the abdomen; 8, anal extremity; _a_, antennae; _b_,
tarsus; _c_, tibia; _d_, femur; _e_, palpi; _f_, head; _g_, thorax.]
A cursory glance at this portion of the creature's anatomy will show
that it consists of three distinct and well-defined parts. In front
there is the head, the size of which is somewhat small in proportion.
Two very large eyes make up the greater portion of its bulk. It is
remarkable, too, that butterflies possess eyes proportionately much
larger than those of moths. Now, since butterflies always fly by day,
and moths are, generally speaking, nocturnal insects, we might be led to
suppose that the reverse of this arrangement would have suited the
creatures better; for a small eye, we should think, would be able to
collect sufficient light in the daytime to form a bright image, and a
larger light-receiving area would be necessary during the darker hours
for the same purpose. But it is evident that the sense of vision must
depend on other conditions besides the size of the eye; and as these
conditions are not understood in relation to the eyes of insects, any
attempt at an explanation would be quite useless.
The eye of a butterfly or moth is worthy of a closer examination, for it
is a most beautiful and marvellous structure. The outer globular
transparent membrane--the _cornea_--is divided into a large number of
minute polygonal _facets_, each one of which admits light into a small
conical compartment surrounded by a coloured membrane, and supplied with
a fibre of the nerve of vision (the _optic_ nerve). Hence the eye is
often spoken of as _compound_.
If you look closely into the eyes of various butterflies and moths you
will generally see a ground colour of grey, blue, brown, or black; but
when viewed at certain angles in a strong light the most gorgeous hues
of metallic brilliancy--gold, copper, and bronze--are to be observed.
All such colours are due to the reflection of light from the colouring
matter that lies between the numerous conical compartments.
[Illustration: FIG. 4.--SECTION OF THE EYE OF AN INSECT.]
A glance at the section of a compound eye will show you that all the
little cones radiate from a common centre. And, as each little
compartment is surrounded by opaque colouring matter, it is clear that
perpendicular rays only are capable of penetrating to its base and
exciting the nerve fibre that lies there. Thus each little division of a
compound eye forms its own image of the object that happens to be
exactly opposite its facet. But how many facets do we find in a single
eye? Sometimes only a few hundreds, but sometimes as many as seventeen
or eighteen thousand! We must not, however, conclude that the nature of
the vision of butterflies and moths is necessarily very different from
our own. We have two eyes, but the images formed by them are both
blended, so that we do not see double. We can understand, therefore,
that the thousands of images formed in a single eye may be blended
together so as to form one continuous picture. Still there remains this
difference: while in our own case the two images formed by the two eyes
are practically the same, in the case of insects every one of the little
conical tubes of a compound eye forms an image of an object that cannot
possibly be formed by any one of the others. Thus, if the lepidopterous
insect sees a continuous picture of its surroundings, such a picture is
produced by the overlapping and blending, at their edges, of hundreds or
thousands of distinct parts.
There is yet another interesting difference between the vision of these
insects and that of ourselves. As already stated, our two eyes are both
turned toward the same point at the same time. But look at the
butterfly's eyes. Here are no movable eyeballs, and the two eyes, placed
as they are at the _sides_ of the head, are always turned in _opposite_
directions. The corneae, too, are very convex; and consequently the range
of vision is vastly wider than ours. A boy is often easily surprised by
a playmate who approaches him stealthily from behind, but did you ever
try the same game with a butterfly? I have, many a time. After getting
cautiously so near to a butterfly at rest as to be able to distinguish
between its head and its hinder extremity, I have quietly circled round
it so as to approach it from behind, being at the time under the
impression that it wouldn't see me under those circumstances. But not
the slightest advantage did I derive from this stratagem, for the
position and construction of its eyes enabled it to see almost all ways
at once.
In addition to the two compound eyes, the _Lepidoptera_, or at least
most of them, are provided with two small simple eyes; but these are
generally so hidden among the closely set hair that covers the head,
that it is doubtful whether they are of much service as organs of
vision.
[Illustration: FIG. 5.--ANTENNAE OF BUTTERFLIES.]
[Illustration: FIG. 6.--ANTENNAE OF MOTHS.]
The antennae proceed from two points close to the upper borders of the
eyes. They are jointed organs, and are of very different forms in the
various species of _Lepidoptera_. They are generally long, slender, and
clubbed at the extremity in butterflies, but exhibit several minor
points of difference which we shall have to note later on. In moths the
antennae are sometimes long, slender, and pointed. Some are thick, and
more or less prismatic in form; while others are slightly or deeply
pectinated or comb-like. The antennae of butterflies are always
straight, or only slightly curved; and, although the insects can sway
them bodily, they have no power to bend them, or to stow them away in
any place of shelter. Moths, on the other hand, when at rest, are almost
invariably found to have their antennae snugly tucked under the wings,
and brought so closely against the side of the head for this purpose
that even the uncovered portion is often difficult to find.
There are two other prominent appendages belonging to the heads of the
_Lepidoptera_. These are the _labial palpi_ or feelers of the lips. They
are generally easily seen, projecting forward on the under side of the
head, sometimes so long and conspicuous as to give one the idea of a
snout or long nose. The palpi are jointed--usually in three parts--are
covered with scales, and often furnished with hairs or bristles.
If you watch a moth or butterfly when it is feeding on the sweet juices
of a flower, or on some kind of artificial sweet with which you have
provided it, you will observe its long trunk or _proboscis_, by which
food is sucked up. This instrument is so long and slender that it seems
almost impossible that it can be a tube through which a liquid freely
passes. But a careful examination will show that this is the case. It is
composed of two separate pieces--two half tubes, which, when closely
applied to each other, form a very thin and flexible pipe, perfectly
air-tight and adapted for suction. Sometimes you can see a butterfly or
moth manipulating with its proboscis as if it required readjustment in
some way or other. It has split the tube throughout its length, so that
it now looks like two exceedingly fine hairs. Then, after a short time,
the two halves are put together again, and immediately, as if by magic,
become a single tube in which no kind of seam is to be observed without
a powerful magnifier.
In order to observe the nature of such a wonderful arrangement we must
have recourse to the aid of a good microscope. Thus assisted, we can see
at once how the junction of the two sides of the proboscis is brought
about so quickly and so perfectly. The inner edges of each half are very
regularly fringed with lines of closely set hairs--so regular, in fact,
are they, that they give one the idea of long yet minute beautifully
formed combs. When the two parts are brought together, the hairs of two
opposite edges interlock, those on one side exactly filling the spaces
between those of the other.
The microscope also reveals another interesting fact, viz. that the
proboscis is not a single tube, but, although so remarkably thin, is
really a set of three distinct pipes, one lying on each side of the
central one. It is said that the central tube only is used for sucking
up the liquid food, and there seems to be some doubt as to the uses of
the other two. Some naturalists are of opinion that the latter are air
tubes, and are connected with the respiration of the insect; while
others say that through these the insects eject a thin watery fluid with
which to dissolve or dilute those sweetmeats that are not sufficiently
liquid to be readily sucked up. But possibly both these opinions are
correct, the proboscis serving all three of the purposes here named. The
only observation of my own bearing on the subject is this. While a moth
was feeding on a drop of syrup in a strong light, a powerful lens
revealed drops, of liquid, mingled with bubbles of air, passing
alternately _up and down_ the two lateral tubes of the proboscis. At the
same time the upward current of syrup in the central tube was by no
means steady and continuous.
[Illustration: FIG. 7.--SECTION OF THE PROBOSCIS OF A BUTTERFLY.]
When this organ is not in use, it is beautifully coiled into a close
spiral which lies between the labial palpi. The length varies
considerably in different insects, and consequently the number of turns
in the spiral must differ also. Sometimes there are less than two turns,
while some of the longer ones form spirals of from six to ten turns.
In concluding our brief account of the head of lepidopterous insects it
is, I suppose, hardly necessary to add that there is no kind of chewing
apparatus to be described; all the members of this order, at least in
the perfect state, deriving the whole of the little nourishment they
require entirely by suction through the proboscis or 'trunk.'
The second division of the body is the _thorax_. This is much larger
than the head, and consists of three ring-like segments, joined one
behind the other so intimately that the lines of junction are hardly
visible, even after the thick clothing of fine hair has been brushed
off. Behind the thorax is the abdomen, which is composed of several
segments, the junctions between the rings often being most distinct.
From the sides of the thorax proceed the two pairs of wings, the general
structure of which we have already to a certain extent examined. But
when we are a little farther advanced in our insect studies, we shall
have to become acquainted with detailed descriptions given as aids to
the identification of species. Now, such descriptions cannot be
satisfactory, either to the one who gives or to him who receives, unless
expressed in such definite terms as render a misunderstanding
impossible. A botanist cannot give an accurate and concise description
of a flower without the use of certain names and expressions which have
gradually become an almost necessary part of his vocabulary; neither can
an entomologist give a really useful, and, at the same time, a
_succinct_ description of an insect unless he is acquainted with the
names of its parts. Therefore, seeing that we distinguish the various
species of butterflies and moths _mainly_ by the arrangement and colour
of the markings of their wings, it is really necessary that we should
know the names of the different parts of these organs. For this reason I
have inserted drawings of a fore and of a hind wing of a butterfly,
together with the names of the various parts of the wings, and also the
names of the principal rays or _nervures_. Yet I would not advise any
young entomologist to attempt to commit to memory all the names given.
Rather use the diagram for reference when occasion requires, more
particularly when you have an insect in your possession that you desire
to study. In ordinary descriptions of butterflies and moths the names of
the _nervures_ are not so generally used as those of the _parts_ of the
wing. Consequently it is exceedingly useful to know what is meant by the
terms _base_, _costal margin_, _apex_, _hind margin_, _anal angle_,
_inner margin_, _discoidal cell_ &c. as applied to the wing.
The two pairs of wings are attached to the second and third segments of
the thorax; but of the _three_ pairs of legs, which we have next to
consider, one pair arises from each of the three segments. The
arrangement of these limbs is well shown in the sketch on page 3, as are
also the names of the different parts of the limb, the latter being
given for reference by the reader when the need arises.
All insects, in their perfect state, we are told, have three pairs of
legs; but if you examine the under surface of certain butterflies, such
as the Marbled White, or any of the Vanessas, Browns, or Heaths, it is
quite likely that you will raise objection to such a statement; for in
these you may possibly see only four legs. But this is the result of a
too cursory observation. Look a little more closely at your specimen,
and you will see a pair of smaller legs folded up under the fore part of
the thorax. By means of a blunt needle you can straighten out these
limbs, and then the difference in length to be observed between them and
the other four is very striking indeed. They are also thinner than the
middle and hind legs; and, unlike these, are not provided with claws.
[Illustration: FIG. 8.--DIAGRAM OF THE WINGS OF A BUTTERFLY.
I. _Fore wing._--1-5, subcostal nervules; 6, 7, discoidal nervules;
8-10, median nervules; 11, submedian nervure; 12, internal nervure;
13-15, disco-cellular nervules; 16, interno-median nervule; 17, median
nervure; 18, subcostal nervure; _a_, costal nervure; _b_, costa or
anterior margin; _c_, apex or anterior angle; _d_, posterior or hind
margin; _e_, posterior or anal angle; _f_, interior or inner margin;
_g_, base; _h_, discoidal cell.
II. _Hind wing._--1, 2, subcostal nervules; 3, discoidal nervule; 4-6,
median nervules; 7, submedian nervure; 8, precostal nervure; 9,
subcostal nervure; 10, median nervure; 11, 12, disco-cellular nervules;
_a_, costal nervure; _b_, costa or anterior margin; _c_, apex or
anterior angle; _d_, hind margin; _e_, tail or caudal appendage; _f_,
anal angle; _g_, abdominal or inner margin; _h_, base.]
These imperfectly developed legs are, of course, quite useless as far as
walking is concerned; indeed, it is extremely doubtful as to whether
they are of any service whatever to the owner. On one occasion,
however, while watching a Peacock Butterfly apparently engaged in
cleaning its divided proboscis, I observed that this organ was
frequently passed under the thorax, and that the front pair of legs were
pressed against it on each side, while it was being drawn outward
between them. It is probable, therefore, that these limbs constitute a
pair of brushes by means of which the fine grooves of the divided trunk
are cleared of any solid or sticky matter that may lodge therein. It is
certain that moths, and those butterflies that possess six _equal_ legs,
use the front pair for this same purpose. The former, also, employ them
for brushing their antennae, which seem to be, by the way, particularly
sensitive to different kinds of irritation.
[Illustration: FIG. 9.--THE UNDEVELOPED FORE LEG OF A BUTTERFLY.]
It is a well-known fact that tobacco smoke has a powerful influence on
certain small insects; and even though it can hardly be regarded as a
perfect all-round insecticide, it is certainly more or less
objectionable to the larger and hardier species. A short time since,
while watching a number of newly emerged moths of the _Sphinx_ group,
and at the same time enjoying the solace afforded by the luxurious weed,
a puff of the smoke was accidentally allowed to play into the box in
which my pets were for the time imprisoned. Immediately they rubbed
their front legs vigorously over the antennae, as if to remove the
obnoxious irritant that had thus intruded on their presence. Similar
observations have led many naturalists to suppose that the antennae are
the seat of various senses, such as those of touch, hearing, and smell.
Seeing that insects do not, as far as we know, possess special organs
for all the five senses which we enjoy (and it is interesting to note
here that some insects certainly experience other sensations which are
quite beyond our ken), we can quite understand the common tendency to
locate the seats of certain of the senses in such easily affected parts
as the antennae. But little, I believe, has been definitely proved save
that the antennae are sensitive to touch and to irritants generally.
While speaking of the senses of insects, I cannot refrain from
mentioning a most remarkable example of a peculiar sensitiveness that
has been observed in certain moths of the family _Bombyces_ (page
217)--notably the Oak Eggar, the Emperor, and the Kentish Glory. Take a
newly emerged female of either of these species, shut her up in a small
box, conceal the box in your pocket, and then walk about in some
country spot known to you as being one of the haunts of that species of
moth. Then, if any of the males of the same species happen to be in the
neighbourhood, they will settle or hover about close to the female
which, although still concealed and quite out of their reach, has
attracted them to the spot.
What a marvellously acute sense this must be, that thus enables the
insects to scent out, as it were, their mates at considerable distances,
even when doubly surrounded by a wooden box and the material of a coat
pocket! You would naturally expect that entomologists have turned this
wonderful power to account. Many a box has been filled with the
beautiful Kentish Glories of the male kind, who had been led into the
snare by the attractions of a virgin Glory that they were never to
behold. Many an Emperor has also been decoyed from his throne to the
place of his execution, beguiled by the imaginary charms of an Empress
on whom he was never to cast one passing glance. And these and other
similar captures have been made in places where, without the employment
of the innocent enchantress, perhaps not a single male could have been
found, even after the most diligent search.
Speaking of this surprising sense, I am again tempted to revert to the
antennae; for it is a remarkable fact that the males of those species of
moths which exhibit the power of thus searching out their mates, are
just those that are also remarkable for their very broad and deeply
pectinated antennae--a fact that has led to the supposition that the
power in question is located in the antennae, and is also proportional to
the amount of surface displayed by these organs.
Up to the present time we have been considering the butterfly and moth
in their perfect forms, but everybody knows that the former is not
_always_ a butterfly, nor is the latter always a moth; but that they
both pass through certain preparatory stages before they attain their
final winged state.
We shall now notice briefly what these earlier stages are, leaving the
detailed descriptions of each for the following chapters.
The life of the perfect butterfly or moth is of very short duration,
often only a few days, nearly the whole of its existence having been
spent in preparing itself for the brief term to be enjoyed
... in fields of light,
And where the flowers of Paradise unfold.
It may be interesting to consider of what use the metamorphoses of
insects are, and to what extent these metamorphoses render them fit for
the work they have to do.
It is certain that the chief work of insects, taken as a whole, is to
remove from the earth the excess of animal and vegetable matter. If they
are to do this work effectually, it is clear that they must be very
voracious feeders, and also be capable of multiplying their species
prodigiously. Now each of these powers requires the special development
of a certain set of organs, and an abnormal development of one set must
necessarily be produced at the expense of the other. Hence we find
insects existing in two distinct stages, with or without an intermediate
quiescent state, during the first of which the digestive apparatus is
enormously developed, while the reproductive organs occupy but very
little space; then, during the other stage, the digestive apparatus is
of the simplest possible description, and the organs of reproduction are
in a perfect state of development.
Allowing, then, that the chief work of the insect is the removal of
surplus organic matter, we can see that a large share of its life should
be spent in the larval or grub stage, and that the perfect state _need_
not occupy any more time than is necessary for the fertilisation of the
eggs that almost completely fill the body of the female at the time of
her emergence from the chrysalis shell.
Many insects undergo their metamorphoses by slow degrees, but the
_Lepidoptera_, after existing for some considerable period without any
important visible change in structure, pass by a rapid transition into
the next state. Thus, a caterpillar, that has not altered in general
form for several weeks, changes into a chrysalis within the course of a
few days; and again, after a period of quiescence that may extend
throughout the whole of the colder months, becomes a perfect butterfly
or moth within twenty minutes of the moment of its emergence.
But this suddenness is more apparent than real, as may easily be proved
by internal examinations of the insect at various stages of growth;
showing that we are led astray by the rapidity of _external_
changes--the mere _moultings_ or castings of the skin--while the gradual
transformations proceeding within are not so readily observed.
We have already said that the life of the perfect butterfly or moth is
short. A few days after emergence from the chrysalis case, the female
deposits her eggs on the leaves or stems of the plant that is to sustain
the larvae. Her work is now accomplished, and the few days more allowed
her are spent in frolicking among the flowers, and sucking the sweet
juices they provide. But males and females alike--bedecked with the most
gorgeous colours and overflowing with sportive mirth when first they
take to the wing--soon show the symptoms of a fast approaching end.
Their colours begin to fade, and the beauty-making scales of the wings
gradually disappear through friction against the petals of hundreds of
flowers visited and the merry dances with scores and scores of playful
companions. At last, one bright afternoon, while the sun is still high
in the heavens, a butterfly, more weary than usual, with heavy and
laborious flight, seeks a place of rest for the approaching night. Here,
on a waving stalk, it is soon lulled to sleep by a gentle breeze.
Next morning, a few hours before noon, the blazing sun calls it out for
its usual frolics. But its body now seems too heavy to be supported by
the feeble and ragged wings, and, after one or two weak attempts at
play, incited by the approach of a younger and merrier companion, it
settles down in its final resting place. On the following morning a dead
butterfly is seen, still clinging by its claws to a swinging stem, from
which it is eventually thrown during a storm.
The tale of the perfect moth is very similar to the above, except that
it is generally summoned to activity by the approach of darkness.
We see, then, that butterflies and moths exhibit none of that quality
which we term parental affection. Their duty ends with the deposition of
the eggs, and the parents are dead before the young larvae have
penetrated the shell that surrounds them.
Yet it is wonderful to see how unmistakably the females generally lay
their eggs on the very plants that provide the necessary food for their
progeny, as if they were not only conscious of and careful concerning
the exact requirements of their offspring, but also possessed such a
knowledge of botanical science as enabled them to discriminate between
the plant required and all others.
Has the perfect insect any selfish motive in this apparently careful
selection of a plant on which to lay its eggs? Does the female herself
derive any benefit from the particular plant chosen for this purpose? In
most cases, certainly not. For it often happens that the blossom of this
plant is not by any means one of those that supply the sweets which
insects love, and still more frequently does it occur that the eggs are
deposited either before the flowers have appeared or after they have
faded.
Neither can we easily impute to the insect an acquired knowledge of the
nature and wants of her offspring, or an acquaintance with botany
sufficient to enable her to distinguish plant forms. Our only solution
of the problem (which is really no solution at all) is to attribute the
whole thing to that inexplicable quality which we are pleased to term
_natural instinct_. It is to be observed, however, that it is not _all_
butterflies and moths that display this unerring power. Some few seem to
deposit their eggs indiscriminately on all kinds of herbage. But, I
believe, the larvae of these species are generally grass feeders, and
would seldom have to travel far from any spot without meeting with an
acceptable morsel.
[Illustration: FIG. 10.--THE FOUR STAGES OF THE LARGE WHITE BUTTERFLY
(_Pieris Brassicae_). _a_, larva; _b_, pupa; _c_, imago; _d_, egg.]
But we must now pass on to a brief consideration of the other stages of
the insect's existence. After a time, varying from a few days to several
months, the young caterpillars or larvae make their appearance. They soon
commence feeding in right earnest. Their period of existence in this
state varies from a few weeks to several months, and even, in some
cases, to years. During this time their growth is generally very rapid,
and they undergo a series of _moults_ or changes of skin, of which we
shall have more to say in a future chapter. Then, when fully grown, they
prepare for an apparently quiescent form, which we speak of as the
_pupa_ or chrysalis, and in which they again spend a very variable
period, extending over a few days, weeks, or months. Now, inclosed in a
protective case, each pupa is undergoing a remarkable change. Some of
its old organs are disappearing, and others are developing; and, after
all the parts of the future insect have been developed as far as its
narrow shell will permit, it bursts forth into the world as a perfect
insect or _imago_.
Its wings at first are small, shapeless, and crumpled in a most
unsightly fashion; but it is not long before they assume their full
size, beautiful form, and gorgeous colouring. Then, in about another
hour or two, the wings, at first soft and flaccid, have become
sufficiently dry and stiff to bear their owner rapidly through the air.
We have thus observed some of the more striking features in the
structure of the butterfly and moth in its most perfect state; and
alluded in a very brief manner to the various stages through which these
creatures must necessarily pass before finally reaching this stage. But
now we must study these earlier stages more closely, and watch the
insects during the marvellous transitions they are destined to undergo.
This we shall do in the following chapters.
CHAPTER II
_THE EGG_
I suppose you are all acquainted with the general structure of the hen's
egg, having dissected several, in your own way, many a time.
Its outer covering, which you speak of as the 'shell,' you have observed
is hard and brittle. It is composed of a _calcareous_ or limy substance,
known chemically as _carbonate of lime_. If you put some pieces of it
into an egg cup, and throw over them a little vinegar or any other
liquid acid, you will see them gradually dissolve away, and small
bubbles of carbonic acid gas will rise into the air. Then again, if you
take a long and narrow strip of the shell, and hold one end of it in a
gas or lamp flame, after a short time that end will become softer, and
will glow brightly in the flame, for it is converted into lime--the same
substance that is used by the builders for making their mortar--and the
bright glow is really a miniature _lime light_, such as is always
produced when a piece of lime is made intensely hot.
Just inside this shell you have seen a thin membrane or skin that is
easily peeled off the substance of the egg itself. Next to this comes
the 'white' of the egg, which is really colourless while liquid, but
turns white and more or less solid in the cooking. Last of all, in the
centre of this, you have noticed the oval yellow mass that is termed the
'yoke' or 'yolk,' and which contains the embryo of the future chick.
Now if you imagine this egg to be reduced in size till two or three
dozen of them would be required to form a single line about one inch
long, the outer calcareous shell to be entirely removed, the skin or
membrane to be converted into a firmer substance of a horny nature, and,
finally, the yolk to be absent and the whole internal space to be filled
with the 'white,' you will then have some idea of the nature of the egg
of a butterfly or moth.
To put the matter more briefly, then, we will say that the eggs of these
insects are simply little liquid masses, usually of a colourless
substance, surrounded by a horny and flexible covering.
Such a description may certainly give you some idea of the nature of the
eggs of insects, but no amount of book reading will serve the purpose so
well or be so pleasant as the examination of the eggs themselves. During
the summer months very little difficulty will be experienced in finding
some eggs in your own garden. Turn over some leaves and examine their
under surfaces, choosing especially those plants which show, by their
partially eaten leaves, that they are favourites with the insect world.
Or you may amuse yourself by catching a number of butterflies--common
'Whites' are as good for the purpose as any--and temporarily confine
them in a wooden or cardboard box, containing a number of leaves from
various plants, and covered with gauze. In this way you are sure to
obtain a few females that have not yet laid all their eggs; and if you
watch your prisoners you will soon see them carefully depositing the
eggs on the under surfaces of leaves, bending their abdomens round the
edges if there is not sufficient room to get themselves completely
under. And then, when you are satisfied with the number of eggs thus
obtained for your examination, you can have the pleasure of seeing all
your liberated captives flying joyfully in the free air.
In giving these simple instructions I have assumed that the reader has
not yet learnt any of the characters by which female butterflies are to
be distinguished from their lords and masters; but I hope that he will
know soon, at least with regard to a good many species, from which
individuals he may most reasonably expect to obtain eggs, and so be able
to avoid the imprisonment, even though only temporary, of insects which
cannot satisfy his wants.
Again, it is not necessary, after all, that butterflies should be
captured for the purpose of obtaining eggs. Watch them as they hover
about among your flowers. Some, you will observe, are intent on nothing
but idle frolicking; and you may conclude at once that _these_ have no
immediate duty to perform. Others are flying without hesitation from
flower to flower, gorging themselves with the sweets of life: these are
not the objects of your search. But you will descry certain others,
flying round about the beds and borders with a steadier and more
matronly air, taking little or no notice of their more frivolous
companions, and paying not the slightest heed to the bright
nectar-producing cups of the numerous flowers. These are seriously
engaged with family affairs only. Watch one of them carefully, and as
soon as she has settled herself on a leaf, walk steadily towards her
till you are near enough to observe her movements. She will not move
unless you approach too closely, for, like busy folk generally, she has
no time to worry about petty annoyances. You will now actually witness
the deposition of the eggs exactly as carried on in the perfect freedom
of nature; and the eggs themselves may be taken either for examination
or for the rearing of the caterpillars.
Some species of _Lepidoptera_ lay some hundreds of eggs, and it is
seldom that the number laid by one female is much below a hundred.
As already stated, the under surfaces of leaves are generally chosen for
the deposit of eggs, but a few of the insects we are considering always
select the upper surface for this purpose. Thus the Puss Moth (page
235), and two or three others resembling it, though much smaller, known
as the Kittens (page 234), invariably lay them on the upper surface. And
this is the more surprising since the eggs of these moths are brown or
black, and consequently so conspicuous on the green leaves as to be in
danger of being sighted by the numerous enemies of insects.
The Hairstreak Butterflies (page 183) afford another exception to the
general rule, for their eggs are deposited on the _bark_ of the trees
and shrubs (birch, sloe, elm, oak, and bramble) on which their larvae
feed.
At the moment each egg is laid it is covered with a liquid sticky
substance, so that it is immediately glued to the leaf or stem as soon
as it is deposited. The sticky substance soon dries, causing the egg to
be so firmly fastened in its place that it is often impossible to force
it off without destroying it completely.
Some of the _Lepidoptera_ deposit their eggs singly, or in small
irregular clusters; but by far the larger number set them very regularly
side by side, in so compact a mass that it would be impossible to place
them on a smaller area without piling one on top of another. This is not
accomplished with the aid of the sight, for the insect performing her
task with such precision often has her head on one side of a leaf or
stem while arranging her eggs on the other. If you take the trouble to
watch her, you will see that she carefully _feels_ out a place for each
egg by means of the tip of her abdomen immediately before laying it.
The eggs are laid by moths and butterflies at various seasons of the
year. In some cases they are deposited early in the spring, even before
the buds of the food plants have burst; and the young larvae, hatched a
few weeks later, commence to feed on the young and tender leaves. Then,
throughout the late spring, the whole of the summer and autumn, and even
till the winter frosts set in, the eggs of various species are being
laid.
Those deposited during the warm weather are often hatched in a few days,
but those laid toward the autumn remain unchanged until the following
spring.
In this latter case the frosts of the most severe winter are not capable
of destroying the vitality of the eggs. In many instances the perfect
insect or the larva would be killed by the temperature of an average
winter day, but the vitality of the eggs is such that they have been
subjected to a temperature, artificially produced, of fifty degrees
below the freezing point, and even after this the young larvae walked out
of their cradles at their appointed time just as if nothing unusual had
occurred.
Experiments have also been performed on the eggs with a view of
determining how far their vitality is influenced by high temperatures.
We know that the scorching midsummer sun has no destructive influence on
them, but these experiments prove that they are not influenced by a
temperature only twenty degrees below the boiling point--actually a
considerably higher temperature than is _necessary_ to properly cook a
hen's egg.
Let us now examine a number of eggs of different species, that we may
note some of the many variations in form and colour.
With regard to colour, we have already observed that the eggs of a few
species are black; but more commonly they are much lighter--pearly
white, green, yellow, and grey being of frequent occurrence.
The great variety of form, however, will provide a vast amount of
enjoyment to anyone who possesses a good magnifying lens or a small
compound microscope. Some are globular, others oval; while many others
represent cups, basins, and domes. Then we have miniature vases, flasks,
bottles with short necks, and numerous figures that must remind a
juvenile admirer of the sweet cakes and ornamental jellies that have so
often gladdened his longing eyes.
Again, the beautifully sculptured surfaces of a large number are even
more striking than their general shapes. Some are regularly ribbed from
top to bottom with parallel or radiating ridges, and at the same time
marked with delicate transverse lines. Others are beautifully pitted or
honeycombed, some ornamented with the most faithful representation of
fine wicker-work, while a few are provided with a cap, more or less
ornamental, that is raised by the young larva when about to see the
world for the first time. A few of these beautiful forms are here
illustrated and named, and another has already appeared on page 14, but
an enthusiastic young naturalist may easily secure a variety of others
for his own examination.
[Illustration: FIG. 11.--EGG OF THE MEADOW BROWN BUTTERFLY.]
[Illustration: FIG. 12.--EGG OF THE SPECKLED WOOD BUTTERFLY.]
[Illustration: FIG. 13.--EGG OF THE VAPOURER MOTH.]
It may be surmised from the accompanying illustrations that the form of
the egg is always the same for any one species. This is really the case,
and consequently an experienced entomologist can often decide on the
name of the butterfly or moth that deposited a cluster of eggs he
happens to find in his rambles and searchings; but in such decisions he
is always greatly assisted by a knowledge of the food plants of the
various insects, and sometimes also by the manner in which the eggs are
arranged.
We have seen that the period during which the _Lepidoptera_ remain in
the egg stage is very variable, and depends largely on the season in
which they were laid; but it is often possible to tell when to expect
the young larvae by certain changes which take place in the appearance of
the egg. As the horny covering of the egg is transparent, the gradual
development of the caterpillar from the clear fluid can be watched to a
certain extent; but if you have a microscope, and would like to witness
this development to perfection, proceed as follows.
Arrange that some butterflies and moths shall lay their eggs on strips
of glass of convenient dimensions for microscopic work--three inches
long by one wide is the usual size for this kind of work. This is easily
accomplished by placing a proper selection of female insects in a rather
small box temporarily lined with such 'slips.' When a few eggs have thus
been secured, all you have to do is to examine them at intervals with
your microscope, always using the reflector so as to direct a strong
light _through_ the eggs from below.
But even without such an arrangement some interesting changes are to be
observed. As a rule, the colour of the egg turns darker as the time for
the arrival of the infant larva approaches, and you will often be able
to see a little brown or black head moving slightly within the 'shell.'
You may know then that the hatching is close at hand, and the movements
of the tiny creature are well worth careful watching. Soon a small hole
appears in the side of the case, and a little green or dark cap begins
to show itself. Then, with a magnifier of some kind, you may see a pair
of tiny jaws, working horizontally, and not with an up-and-down motion
like our own, gradually gnawing away at the cradle, till at last the
little creature is perfectly free to ramble in search of food.
Strange to say, the young larva does not waste a particle of the horny
substance that must necessarily be removed in securing its liberty, but
devours it with an apparent relish. Indeed, it appreciates the flavour
of this viand so highly that it often disposes of the whole of its
little home, with the exception of the small circular patch by which it
was cemented to the plant. When the whole brood have thus dispensed with
their empty cradles, there remains on the stem or leaf a glittering
patch of little pearly plates.
After the performance of this feat the young caterpillar starts off in
life on its own account with as much briskness and confidence as if it
had previously spent a term in the world under the same conditions; but
we must reserve an account of its doings and sufferings for our next
chapter.
CHAPTER III
_THE LARVA_
In almost every case the young caterpillar, on quitting the 'shell' of
the egg, finds itself standing on and surrounded by its natural food,
and immediately commences to do justice to the abundant supply. It will
either nibble away at the surface of the leaf, removing the soft
cellular substance, so that the leaf exhibits a number of
semi-transparent patches when held up to the light, or it will make
straight for the edge, and, closing its horizontal jaws on either side,
bite the leaf completely through, and thus remove a small piece each
time.
[Illustration: FIG. 14.--THE CATERPILLAR OF THE CLOUDED YELLOW
BUTTERFLY.]
Several naturalists have amused themselves by performing experiments and
making calculations on the efficiency of the masticating and digesting
powers of the caterpillar. The illustrious R['e]aumur, for example, proved
that some of the cabbage eaters disposed of more than twice their own
weight of food in twenty-four hours, during which time their weight
increased one-tenth. Let us see what this would be equivalent to in
human beings: A man weighing eleven stone would devour over three
hundred pounds of food in a day, and at the end of that day weigh about
fifteen pounds more than he did at the beginning!
So the young caterpillar eats, and rests, and grows, till, while still
young, its body has become too large for the already tightened skin. It
evidently feels very uncomfortable. Its appetite fails, and it remains
for a time perfectly quiet in one spot, having previously spun a little
carpet of silk to form a firm foothold during its temporary
indisposition. Its colours have also become dingy, and anyone, not
understanding the character of its growth, might easily be led to
suppose that the poor creature was displaying the earlier symptoms of a
serious and perhaps fatal illness.
But soon an encouraging symptom is observed. The caterpillar begins to
get restless. Its front segments are turned alternately right and left,
and are also made to swell out much beyond their normal size. Then in a
very short time--often less than a minute from the first appearances of
restlessness--the skin, which has become somewhat dry and brittle,
splits along the back over the second, third and fourth segments,
revealing a new and bright coat beneath. The caterpillar continues its
struggles and, in addition to the previous movements, causes the
swelling to move backward along the body. This, acting like a wedge,
causes the rent in the old coat to extend in that direction.
[Illustration: FIG. 15.--THE CATERPILLAR OF THE DARK GREEN FRITILLARY
BUTTERFLY.]
The caterpillar now draws its head backward, and, with a few convulsive
struggles, pulls the front segments out of their old skin, and passes
its head out of the rent in the back. With its foremost segments thus
rendered perfectly free, it walks straight out of the old garment, which
is left still fixed by the legs to the silken carpet.
The larva, although now fresh and smart in its appearance, is exhausted
by these struggles and its prolonged fast. The new skin, moreover, is
very soft and tender, even to the cases of the head and legs, which are
normally very hard. But a short period of rest suffices to dry its skin
and sharpen its appetite, and then it eats more vigorously than ever.
We will now leave the caterpillar for a moment while we look at its
cast-off clothes. They are still clinging to a stem so firmly that they
can scarcely be removed without injury. The hard shell that covered the
head and jaws is perfect in form, and so are the claws and cases of the
legs. All the hairs or spines that happened to adorn the previous owner
still retain their positions; and the whole skin, although always more
or less shrivelled, is sometimes so slightly altered in form that it
might be mistaken for a living caterpillar if not closely examined.
But this is not all. For, according to the accounts of some
authoritative observers, the lining of the digestive organs, which is
really a continuation of the outer skin, is cast off (or rather cast
_out_) at the same time, as are also the linings of the larger breathing
tubes which are presently to be described.
We have seen that some caterpillars, on quitting their egg cases (which
may really be regarded as the first moult), make their first meal of the
old covering. So also some of them, in their future moultings, exhibit
an apparently useless economy (seeing that they are surrounded by an
abundance of their natural vegetable diet) by devouring their old coats!
In the face of this fact we can hardly describe them as strict
vegetarians.
[Illustration: FIG. 16.--THE CATERPILLAR OF THE PURPLE EMPEROR
BUTTERFLY.]
Having thus passed through its first hardship, the caterpillar has by no
means seen the end of the troubles and dangers that beset it; for,
during its existence in the larval state, it has to go through a series
of three, four, five, or even six moults, all of which are periods of
considerable inconvenience, and perhaps even pain, and frequently prove
fatal. And it is by no means an uncommon thing to meet with the lifeless
body of an unfortunate individual who, as shown by its shabby appearance
and the silken carpet under its feet, has evidently fallen a victim to
the dangerous process of ridding itself of an old garment.
But this is only one of the many dangers to which caterpillars are
exposed. Throughout every hour of the day the sharp and hungry eyes of
the numerous insect-eating birds are searching the leaves for such
delicacies to satisfy the wants of themselves and their broods. The
lively little lizards, too, during the sunny hours are busily engaged in
searching them out among the foliage of heaths and banks.
Very formidable enemies also exist in the form of Ichneumon and other
species of flies, which pierce the skins of caterpillars with their
sharp _ovipositors_, and lay their eggs within the bodies of the
unfortunate victims. As soon as the young larvae are hatched from these
eggs, they commence feeding on the fatty substance stored beneath the
caterpillar's skin. They carefully avoid, at first, attacking the vital
organs of their host's body, and in this way secure for themselves a
more lasting supply of fresh food. When the fatty substance is nearly
all gone, they eat their way into the more important structures, of
course steadily growing all the time; and so, even though the body of
the caterpillar is rapidly diminishing, the total bulk shows often no
very appreciable decrease in size. When the larvae of the flies are fully
fed, they either change to the pupa within the carcase of their host, or
eat their way out of its body and construct for themselves a cocoon in
which to undergo the transformation.
As for the caterpillar itself, it sometimes dies before the time for its
metamorphosis has arrived; but it often changes to the chrysalis before
its fate is sealed. In this latter case, a number of flies, having
undergone their final transformation within the chrysalis shell (there
being but little else than shell remaining of the victim's body), break
forth from the remains of the carcase somewhere about the time at which
the butterfly or moth should have appeared.
[Illustration: FIG. 17.--AN ICHNEUMON FLY (_Cryptus Migrator_).]
[Illustration: FIG. 18.--ANOTHER ICHNEUMON FLY (_Pimpla Instigator_).]
Caterpillars have also their nocturnal enemies and devourers, among
which may be mentioned frogs, toads, newts, and insect-eating mammals.
We must now learn something of the structure of caterpillars; and then
become acquainted with their habits, and the change to the chrysalis or
pupa.
Take a caterpillar from your garden, preferably a full-grown one of a
rather large species, that is not very densely covered with hair, and
examine it carefully as we note the main points in its structure. The
first point that strikes our notice is the division of its body into
segments or rings, separated from each other by a more or less distinct
line or slight constriction of the body.
There are thirteen of these segments, reckoning, as is usual, the head
as the first.
The head is usually very hard, and often of a much darker colour than
the rest of the body. It is also frequently divided into two lobes by a
couple of oblique lines, between which the parts of the mouth are
situated. The two powerful horizontal jaws, to which we have already
referred, are very hard and sharp, and curved like a sickle, and
therefore splendidly adapted for biting from the edges of leaves. The
head is also provided with a pair of antennae, usually very short and
inconspicuous and protected by a horny covering.
Unlike the perfect insect, the caterpillar has no large compound eyes,
but twelve very small simple eyes, situated on the cheeks, very near the
mouth--six on each side.
[Illustration: FIG. 19.--THE CATERPILLAR OF THE ANGLE SHADES MOTH
(_Meticulosa_).]
If you examine them with a magnifier, you see that each one is provided
with a small and very convex lens--a lens of very _short focus_, such as
would be used for the examination of small objects held very near to the
eye. From this arrangement we should be inclined to conclude that the
caterpillar can see only those objects that are close to its mouth; and
this idea is strengthened if you place one in a box containing a number
of leaves, one of which is that of its own food plant. It will wander
about the box, apparently looking at every part of every leaf it passes,
after the manner of a very short-sighted individual, and never taking a
general look round. A butterfly or a moth can see a flower in the
distance, for it flies unhesitatingly from one to another in the
straightest and shortest path, but if you place a caterpillar in the
centre of a ring composed of a leaf of its food plant and nine others
from other plants, the chances are (nine to one) that it will _not_ walk
towards what it would like to have.
Again, the eyes are situated on the _lower_ part of the cheek, directed
slightly downward, and are therefore adapted for seeing what is just
under its jaws as it walks along. Had we no knowledge whatever of the
caterpillar's twelve little eyes, we should probably have thought that
it sought out its food by some sense other than that of vision.
Another important and interesting feature of the head is the
silk-spinning apparatus, situated under cover of the lower lip. This
consists of two tubular glands, corresponding to our own salivary
glands, the special purpose of which is to secrete a viscid fluid that
solidifies on exposure to air. The opening by which the fluid escapes is
so situated that the caterpillar can easily apply it to the surface of
any object over which it is walking, and then, by drawing or turning
away its head, cause a silken fibre to be produced.
Some caterpillars make use of this spinning apparatus only on a few
special occasions, but others, more especially some of the smaller
species, seem to have it always in use, so that if at any time you
suddenly start them into the air by giving a smart tap to the plant or
twig on which they rest, they invariably fall slowly on the end of a
growing web, the spinning of which they stop as soon as they consider
they have fallen far enough. Sometimes, as you are walking through a
wood, you will see hundreds, nay, thousands of little caterpillars thus
suspended, swinging gently in the breeze. Not long since, after only a
few minutes' walk among the trees of Epping Forest, I found I was
decorated with several dozens of these swingers with which I had come
into collision--in this case consisting chiefly of the larvae of the
Green Tortrix Moth (_Tortrix viridana_).
Now let us examine the caterpillar's limbs. Attached to each of the
second, third, and fourth segments is a pair of true walking legs,
corresponding with those of the perfect insect. These are covered with a
hard and shining substance, and are also each provided with a hook. The
fifth and sixth segments have no limbs at all, nor have the eleventh and
twelfth, but some or all of the others (seventh, eighth, ninth, tenth,
and thirteenth) are furnished with a pair of claspers which we shall
presently describe.
First, as regards the number of claspers, it will be seen from what has
just been said that this is not always the same. Some caterpillars
possess five pairs, thus making up the total number of walking
appendages to sixteen. In fact, we must regard this as the _usual_
number. But there are at least a few hundred exceptions to the rule.
Many of the _Bombyces_ (page 217), for example, have only four pairs of
claspers; and in others of the same group the fifth pair is present, but
only partially developed, and quite useless for walking.
Look at the peculiar caterpillar of the Lobster Moth (fig. 23)--a
creature that differs from most other caterpillars not only in its
claspers, but in many other respects too. Observe its long and slender
legs, its humped middle segments, and its upturned hindermost segment,
of enormous size and mounted with a pair of clubbed 'horns.' This last
segment you will observe, has no claspers.
[Illustration: FIG. 20.--WALKING LEG OF A CATERPILLAR.]
[Illustration: FIG. 21--LARVA OF THE YELLOW UNDERWING MOTH (_Pronuba_).]
[Illustration: FIG. 22.--LARVA OF THE CRIMSON SPECKLED MOTH
(_Pulchella_).]
[Illustration: Fig. 23.--LARVA OF THE LOBSTER MOTH (_Fagi_).]
Another allied caterpillar is that of the Iron Prominent Moth (fig. 24).
This one also has humped segments, and the claspers of the thirteenth
segment are imperfectly developed.
A large number of other exceptions to the general rule are to be found
in the caterpillars of the Geometer Moths (page 268), one of which is
here represented. These have generally only two pairs of claspers, one
pair on each of the tenth and last segments, so that there is a distance
equal to the combined length of six segments between the hindermost true
leg and the first pair of claspers. But even among the Geometers there
are variations to be observed in the number of claspers, and some of
these will be pointed out in our brief descriptions of the commoner
species.
[Illustration: FIG. 24.--CATERPILLAR OF THE IRON PROMINENT MOTH
(_Dromedarius_).]
[Illustration: FIG. 25.--LARVA OF THE BRIMSTONE MOTH (_Luteolata_).]
These limbs which we have been calling claspers are known by several
other names. Thus they are termed 'pro-legs,' 'temporary legs,' 'false
legs,' and 'abdominal legs;' but if you watch a caterpillar as it walks
up a stalk or along the edge of a leaf, you will certainly agree that
the term 'clasper' is everything that could be desired. But why not call
them legs, seeing that they are used in walking? The reason is that they
differ in many respects from the three foremost pairs of limbs as
regards structure, persistency, and function. The true legs, as we have
called them, continue to exist, though concealed, in the chrysalis
state, and again appear, far more perfectly developed, in the butterfly
or moth, but the claspers are no more to be seen after the caterpillar
has passed into the quiescent stage. We have noticed, too, that the true
legs are pointed and clawed, also that they are protected by a hard and
horny covering; but examine a large caterpillar, holding it between the
fingers and thumb with its under side uppermost, and you will soon see
that the claspers are not at all hard, but soft and fleshy; not pointed,
but often terminating in a broad flat circular surface. You will also
observe, as the creature struggles to escape from your grasp, and tries
to get a hold on something with its claspers, that these limbs, if we
may so call them, are retractile, and are sometimes completely drawn
into the body. Finally, examine the broad end of a clasper with a
magnifier, and you will see it surrounded by a circle of little hooks,
turning in all directions. You will no longer wonder how it is that a
caterpillar can hold so tenaciously to a piece of twig that it is often
almost impossible to remove it without injury.
Now put your caterpillar down, so that you may observe its gait. If it
happens to be one with the full complement of sixteen limbs, you see
that at each stride it makes but little progress. The segments contract
and relax alternately and in succession, thus sending a series of
wave-like motions along the body, and urging onward the front segments
while the claspers keep the hinder portion firmly fixed.
[Illustration: FIG. 26.--THE CLASPERS OF A CATERPILLAR.]
But if your caterpillar is one of the Geometers, with only two, or
perhaps three, pairs of claspers, the mode of procedure is very
different. The creature stretches its body out at full length, often
raising its head high in the air, and swinging its long body right and
left with a most furious motion, as if to hastily scan the
neighbourhood. Then, having satisfied itself as to the _direction_ of
its proposed course (which, by the way, is often changed considerably at
almost every stride), it holds on by the true legs and pulls its hinder
quarters forward till the body forms almost a closed loop, with the
fourth segment nearly touching the ninth. The claspers now become the
holdfasts. The little hooks with which they are provided are firmly
fixed to the surface on which it is walking; and the body being again
straightened out to its utmost length, the same man[oe]uvre is repeated.
So, you see, the insect progresses by strides equal in length to about
six segments of the body, and these the longest segments generally; and
the rate at which the strides succeed each other, especially in some of
the smaller species, is really astonishing.
We have seen the caterpillar in the act of taking its walk, and now we
will give it a twig of its food plant so that we may see it feed. It
walks up the twig without hesitation--for caterpillars (excepting those
which feed on roots) always seem to move upward when in search of
food--and soon finds itself on a leaf. Over this it walks till it
reaches the edge; and, grasping the edge firmly between the claspers, so
as to give perfectly free play to its legs and head, it stretches its
body at full length, and takes a series of bites as it brings its head
backward in a curve. When the head has thus been brought close to its
fore legs, the body is again extended, and the same ground is gone over
again.
If the caterpillar is a fairly large and hardy one, it will bite through
the smaller veins, and perhaps even the larger ones; but the smaller
species often change their position on reaching a moderately thick vein,
and so devour little else than the soft cellular substance of the leaf.
In any case, it is astonishing to see how rapidly the leaf disappears
under the influence of the powerful jaws and marvellous digestive
apparatus of the hungry grub.
Those who take a delight in watching the _movements_ of caterpillars are
sure to be interested in observing them when at rest; for at such times
the various attitudes assumed are as pleasing and instructive as are
their active moments. And these attitudes are all the more interesting
on account of the mimicry by which the creatures often baffle their
numerous enemies. We may profitably spend a little time in studying a
few cases in point.
Many species, when at rest, fix themselves by means of their claspers to
a small twig or leaf stalk, or on the midrib of the leaf itself. Here
they remain perfectly still, with their bodies perfectly straight or
with head slightly raised. I need hardly say that these generally fix
themselves on the _under_ side of the leaves and stalks, thus securing
themselves against the attacks of the feathered foes above. But some
birds are equal to the caterpillars in this matter; and it is really
amusing to see them hopping about beneath the leaves in our gardens,
every now and again slyly turning one eye upward, and smartly plucking
an unwary grub from its resting place.
The precautions of the caterpillar, however, do not end merely with the
selection of an under surface. You will find that the bright green
species invariably settle on a leaf or a _green_ stalk, while the darkly
coloured insects often choose a twig covered with a brownish bark. Some
even make for the _trunk_ of the tree on which they feed, and here
remain quite still in a vertical position, so that they look just like a
ridge in the bark, the colour of which is faithfully imitated by their
skin. Further, many of the caterpillars that resort to this stratagem
have bodies that are notched or knotted and spotted in such a manner
that the resemblance to their surroundings is so perfect as to defy any
but the most experienced eye. And even this is not all, for a number of
these mimics of the insect world never venture to feed by day, but take
in their quantum of provisions during the dark hours, and practise their
deceptions throughout the day.
Most of the Geometer caterpillars, of which we have already spoken, are
well trained in the art of deception. You are out on a caterpillar hunt,
and engaged in carefully turning over the twigs of the hazel or some
other shrub, so that you may the more readily examine the under surfaces
of the leaves. At last you lay hold of a small broken twig for this very
purpose. To your astonishment it is very soft, and readily bends between
your fingers. You look more closely at this peculiar piece of stick, and
find, to your surprise, that you have grasped a looper caterpillar that
was standing out at an angle just like a broken twig, supported by its
two pairs of claspers, and coloured and knotted exactly like the little
branch on which it rested.
At other times you meet with little green caterpillars of the same
group, supporting themselves in exactly the same manner on a small twig,
and looking just like a leaf stalk from which the blade had fallen or
been devoured.
What a wonderful power is exhibited in the grasp of the claspers and the
tension of the muscles, enabling the caterpillar to fix itself and
retain its position for so long a time! Imagine an acrobat fixing
himself by his hands on an upright pole, throwing out his body at an
angle, and without any further support retaining his position motionless
for several hours!
Other experiences of the larva hunter are equally interesting and,
perhaps, even more tantalising. He is engaged in very cautiously turning
over the leaves of a certain food plant from which he hopes to obtain
the larva of a much-coveted species. Then, just as his eye catches a
glimpse of the very object of his search, down falls the caterpillar,
rolled up into a little ball, among the herbage below. This latter is
diligently and patiently examined. But no, the anticipated prize is
nowhere to be seen. It is probably a green one, and this adds to the
difficulty of the patient entomologist. Then, as he carefully separates
the low herbs, hoping to find the spot where the larva had fallen, the
insect, rolled up into a compact little ball, only sinks deeper and
deeper into the maze.
Many caterpillars avoid capture in this manner, while others seek to
avoid detection by remaining perfectly motionless, even when roughly
handled. They allow themselves to drop from their resting place on the
slightest sign of danger, and, when the alarm is over and all is quiet
again, they ascend the food plant and resume their position.
Some caterpillars not only rest, but even feed under cover, quite secure
from most, if not all, of their enemies. Several of them feed on roots,
and many a farmer can relate sad experiences of the havoc committed by
these caterpillars on his turnips and other crops. Then there are those
which feed on flowers and buds, completely burying themselves in the
dense mass of food.
[Illustration: FIG. 27.--THE HOMES OF LEAF MINERS AND LEAF ROLLERS.]
We must conclude this brief account of resting and hiding places and
attitudes of caterpillars by a few observations on the leaf miners and
leaf rollers.
The former are very small caterpillars--the larvae of certain small
moths--that eat burrows into leaves without doing any considerable
injury to the outer _epidermis_, and thus prepare a safe resting place
within the substance of their food.
The latter, also mostly of small size, make themselves secure by curling
a leaf or a portion of a leaf into a cylinder, and holding it in
position by means of a number of silken threads.
If you examine a leaf thus curled you will soon be convinced that a
considerable number of the extremely delicate threads must be necessary
to hold it in position; but, if you would like to know how a very small
and feeble caterpillar can manage to roll up a comparatively large and
rigid leaf, you must watch the little creature at its work.
You need have but little difficulty in finding a willing worker, for
such caterpillars are extremely numerous. Take a few out of their
self-made homes, place them on a sprig of the food plant, and you will
soon have the pleasure of seeing one start its extraordinary work.
At first it spins a number of threads stretching from the edge of a leaf
to about the middle of the surface. These threads are not tight by any
means, and the leaf is, as yet, unchanged in position. But now the
little mechanic exhibits a tact that almost seems to prove a knowledge
of the principles of its art. Each thread in turn is pulled _at right
angles_ at its middle, and then fastened by means of the creature's
spinneret. Each time this is done the edge of the leaf is bent round _a
little_; and when at last the cylinder is completed, a number of other
threads are stretched across from the scroll to the flat part of the
leaf to secure it firmly in its place.
Many caterpillars are solitary in their habits: that is, they are always
found singly, whether walking, resting, or feeding. But a large number
of species are gregarious, living in dense clusters either throughout
their larval state or, perhaps, only while young. In many such cases it
is difficult or even impossible to find any reason for this gregarious
tendency--to discover any advantage that the insects may derive from the
habit. Many species, however, are true co-operators in the defence of
their communities. The caterpillars of such live in clusters, sometimes
several scores in each, and all help in the spinning of a complicated
mass of silk fibres, which, with the leaves and twigs they join
together, form a safe home in which they can rest, feed, or change to
the chrysalis state. In early summer hundreds of such caterpillar
'nests' are to be seen in many of our hawthorn and other hedgerows.
Before closing our general account of the caterpillar we must have a
word to say about the breathing apparatus, more especially as in our
future descriptions we shall frequently have to mention the colours and
markings which surround the openings in its body through which the air
supply is admitted.
If you examine the sides of the segments of a caterpillar, using a lens
if the insect is a small one, you will observe some little round holes,
often inclosed in a ring or a patch of some prominent colour. These are
the _spiracles_ or openings of a series of air tubes called _tracheae_.
These latter divide and subdivide within the body of the caterpillar,
the branches of one often uniting with those of another, thus forming a
really complicated arrangement of air pipes by which the supply of
oxygen is distributed.
A microscopic examination of a portion of one of the tracheae will show
that its walls are supported by an elastic spiral of a firm substance.
This arrangement serves to keep the air passages open, and secures for
the caterpillar a free supply of air at times when a contraction of the
segments would otherwise cause the tubes to collapse.
There are nine spiracles on each side of the caterpillar's body, and
never more than one in the side of the same segment. The head, which we
have been regarding as the first segment, has no spiracles. The second
segment has a pair--one on each side. There are none in the third and
fourth; but all the segments, from the fifth to the twelfth inclusive,
have each a pair; the last (thirteenth) segment has none.
We have already observed the general arrangement of the caterpillar's
limbs; but perhaps it may be interesting and even convenient to the
reader to give here a little table that will show at a glance the
disposition of both limbs and spiracles.
First segment--head Two short antennae, two jaws,
and twelve eyes.
Second " Legs and spiracles.
Third " Legs only.
Fourth " Legs only.
Fifth " Spiracles only.
Sixth " Spiracles only.
Seventh " Spiracles, and sometimes
claspers.
Eighth " Spiracles, and sometimes
claspers.
Ninth " Spiracles, and sometimes
claspers.
Tenth " Spiracles, and generally
claspers.
Eleventh " Spiracles only.
Twelfth " Spiracles only.
Thirteenth " Claspers only, and these
occasionally absent.
We must now watch the caterpillar through its later days, to see how it
prepares for passing into the pupal stage, and to witness the various
interesting changes that take place at this period.
When fully grown, it ceases to eat, and begins to wander about in search
of a convenient spot for the coming event. Its colours fade, and the
body becomes appreciably smaller, especially in length, as it ejects the
whole contents of its digestive apparatus. According to some accounts,
it even evacuates the lining of the intestines with their contents.
A great variety of situations are chosen by the different species at
this time. Some will fix themselves on their own food plant, and there
remain till they finally emerge in the perfect state, suspending
themselves from a silken carpet, hiding themselves in a rolled leaf, or
constructing a cocoon of some kind. A large number walk down the food
plants, and undergo their changes in moss that happens to lie at the
foot; or construct a cocoon on the surface of the ground, utilising for
the purpose any decayed leaves, fragments of vegetable matter, or pieces
of earth or small stones. Many seek a further protection than this, and
burrow into the soil, where they either lie in a little oval cell that
they prepare, or in a cocoon constructed by spinning together some
particles of earth. Again, there are those caterpillars, chiefly of
butterflies that frequent our gardens, which find their way to the
nearest wall or fence, and there secure themselves in a sheltered nook.
We will watch a few of these varied methods of procedure, taking as our
first instance the caterpillar of the common Large White or Cabbage
Butterfly.
When fully fed, this larva seeks out a sheltered spot, generally
selecting the under surface of some object, or of the ledge of a wall or
fence. Sometimes it will not even leave its food plant, though it
generally walks some considerable distance before a suitable shelter is
found. Having satisfied itself as to the site of the temporary abode, it
sets to work at spinning a silken carpet. At first the threads spread
over a rather wide area, and seem to be laid in a somewhat irregular and
aimless manner; but after a little time its labours are concentrated on
one small spot, where it spins several layers of silk fibres.
This done, it fixes the little hooks of the claspers firmly in its
carpet bed, and then proceeds with a highly interesting movement. It is
not satisfied with only the one mode of suspension. In fact, this alone
would hardly be safe, for when it casts its skin, as it is shortly about
to do, its claspers will all disappear; and although it afterwards
secures itself by the 'tail,' it would be dangling in such a manner as
to swing with every breeze--a very unsatisfactory state of affairs,
especially with those that pupate late in the summer and remain in the
pupal state throughout the winter storms.
Its next procedure, then, is to make a strong silk band round the middle
of its body, so as to keep it close to the surface against which it
rests. But how is this to be done? It bends its head round till the
spinning organ can be applied to a point close beside the middle of its
body. Here it fixes one end of a thread; and then, gradually twisting
its body, brings its head round to the other side, still keeping it
close to the same segment, and fastens the other end of the thread
exactly opposite the point at which it started.
The head is now brought back to its former position, thus adding another
thread to the band; and the process is repeated several times, till at
last the caterpillar is satisfied with the thickness and strength of the
cord formed.
Now it straightens out its body as if to rest from its labours; but the
work is not yet complete. Soon it exhibits much restlessness. Its
foremost segments are seen to shorten, and consequently become thicker.
Then the skin splits, and the last moult of the caterpillar commences.
The movements that follow are exactly similar to those we have already
described in connection with one of the earlier moults: the alternate
and successive contractions of all the segments gradually force back the
old coat, and this is finally thrown entirely off by a somewhat vigorous
wriggling of the 'tail.'
Then, for a moment, the creature is supported only by its silken cord.
But this lasts _only_ for a moment. For, as soon as it is quite free
from the old garment, it applies its tail to the densest part of the
carpet it had prepared at the start, and secures its hinder extremity by
means of little hooks.
But what a change has now come over the creature! It is no longer a
caterpillar. Its head is no longer distinct, although we can readily
make out the positions of the eyes. Its mouth and jaws have quite
disappeared, and the legs and claspers are apparently gone. The three
segments that bore the legs are no longer distinctly separable, though
in reality they still exist. The head and thorax are peculiarly shaped;
and, instead of being cylindrical, are angled and ridged; but, beneath
the soft greenish skin--the new garment--we can discern the outline of
a pair of small wings, and see a proboscis and a pair of long antennae.
Also the six long legs of the future butterfly can be traced with care.
The abdomen is conical in form, coming to a sharp point at the end, and
its segments are quite distinct.
No stranger to the metamorphoses of insects would connect the present
form with that of a caterpillar; they are so very unlike. And yet the
time occupied in the whole change, from the spinning of the carpet, does
not occupy more than about thirty or thirty-five hours.
The apparent suddenness of this change is really surprising, but in
reality the transformation is not nearly so sudden as it appears.
Dissection of a caterpillar a few days before the final moult is due
will show that the changes are already going on. In fact, a simple
removal of the skin will prove that the organs of the future butterfly
are developing. Still, in proportion to the short time occupied, the
change is extremely great; and it may reasonably be inquired, Why so
great a change within so short a space of time?--why is not the change
continued steadily and equally through the larval existence? The reason
has already been hinted at. Caterpillars are living eating machines,
whose office is to remove excess of vegetable matter. Consequently they
must have their jaws and bulky digestive apparatus in full development
to the end. If these organs were to _gradually_ disappear as the
caterpillar reaches its non-eating stages, it would simply be starved to
death. So the change from the larval to the pupal state, which we may
regard as the final moult of the caterpillar, is a far greater change
than any of the preceding ones, and occupies a proportionately longer
time, although it is principally confined to the last few days of the
caterpillar life.
A number of caterpillars, and especially those of the butterflies,
suspend themselves when about to change; and the peculiarities of the
modes adopted must be left for our descriptions of species in a future
chapter; but we will find room here for one more interesting example,
taking this time the larva of one of the commonest of the Vanessas (page
166)--the Small Tortoiseshell Butterfly.
The caterpillars of this insect are gregarious when young; and if ever
you meet with one, you are almost sure to be able to obtain a hundred or
so without much searching. But as they grow older they feed singly, yet
generally without straying very far from their birthplace.
When full grown they sometimes stray to a neighbouring plant or fence to
undergo the change to a chrysalis, but more commonly they are perfectly
satisfied with the protection afforded by the leaves of their food
plant. We will now watch one of these as we did the larva of the Large
White Butterfly.
Of course the under side of the leaf is chosen. Here a silken carpet is
spun as before described; but the caterpillar, instead of clinging with
_all_ its claspers, suspends itself in a vertical position by its
hindermost pair only.
Here it hangs, head downwards, awaiting the coming events. The splitting
and casting of the skin goes on just as in the case of the Large White,
but there is this puzzle to be solved: how can the insect shuffle itself
out of its old coat without falling to the ground, leaving the cast-off
garments still hanging by the hooks of the claspers? This really seems a
matter of impossibility, since the little hooks which alone suspend the
insect are thrown off with the skin of the claspers.
The thing is managed in this way. As the skin slowly splits through the
wrigglings of the apparently uncomfortable occupant, it is gradually
pushed backward--that is, upward--till it is in a shrivelled condition,
and the body of the insect is nearly free. But the chrysalis thus
brought to light is provided with little hooks on the end of its 'tail'
by which it can attach itself to the irregularities of the crumpled
coat. Its conical abdomen is also very flexible, and it can, by bending
this, seize hold of a ridge in the skin, holding it between the
segments. Thus, although practically quite free from the old garb, it
never falls to the ground.
There is now, however, another point to be attended to. The newly formed
chrysalis desires to be entirely independent of its cast-off skin, and
to suspend itself directly from the silky carpet it has prepared. To
this end it works steadily for a time, alternately bending its supple
abdomen from side to side, gripping the folds of the skin between the
segments, pulling its body a little higher at each movement, and
securing itself at each step by the little hooks at its extremity.
So it climbs, and at last it reaches the network of silk fibres, and
thrusts the tip of its abdomen among them till some of the hooks have
taken hold. Not satisfied with this, it turns its body round and round
to get the little hooks so entangled between the silk fibres that a fall
is impossible, and in so doing it frequently pushes the old skin out of
its place so that it falls to the ground.
Although the caterpillars of this species do not show any great
gregarious tendency when nearly full fed, yet it is not an uncommon
thing to find several hanging from the under surface of one leaf, all
being attached to the one common carpet at which all had worked. And
when bred in confinement, a number will often spin in company in a
corner of their cage. I have thus obtained a cluster of thirty-seven
pupae, all hanging by the 'tails' to the same mass of silk, which was so
small that they formed quite a compact mass of beings with their tails
close together.
[Illustration: FIG. 28.--THE COCOON OF THE EMPEROR MOTH.]
[Illustration: FIG. 29.--THE COCOON OF THE SIX-SPOTTED BURNET
(_Filipendulae_).]
We have seen that the Large White Butterfly makes itself secure by a
silk band round its middle, while the 'Tortoiseshell' is fixed only by
its tail. But the extra provision for the safety of the former is not so
necessary in the case of the latter, as it never spends more than two or
three weeks in the pupal state. Here it is the perfect insect that
braves the winter, and not the chrysalis.
There is a great variety in the means taken by the caterpillars of moths
to protect themselves during their metamorphoses, but we shall have
space for only a few illustrations.
A clever cocoon is spun by the larva of the Emperor Moth (_Pavonia_). It
is pear-shaped, and composed of a brownish silk; and is so constructed
that the newly emerged moth can easily walk out of the small end without
breaking a fibre, while the entry of an insect enemy from without is
impossible.
This is managed as follows. A number of rather stiff threads are made to
project from the small end of the cocoon, and these converge as they
pass outward so that the ends are all near together. The other portions
of the cocoon are of compact silk, and any insect intruder that ventures
to enter by what we may almost term the _open_ end is met by a number of
spikes, as it were, that play on it at every attempt. Many of these
wonderful cocoons may be found during the winter months attached to the
food plants of this insect.
Of the silken cocoons spun by various caterpillars some are so thin and
light that the chrysalis can easily be seen through them, and others are
so densely woven as to be quite opaque. A great difference is also to be
observed in the adhesive power of the silk fibres. In some cases little
threads of silk can be pulled off the cocoon; but some of them, that of
the Oak Eggar (page 229) for example, look as if they had been
constructed of paper rather than of silk, because, at the time of
spinning, the moist silk fibres stuck so closely together.
An extreme case of this character is to be met with in the cocoon of the
Puss Moth (page 235); for here the fluid from the spinneret of the
caterpillar does not harden at once on exposure to air, and so the
threads become thoroughly united together, thus forming a solid gluey
cocoon.
When the Puss caterpillar is about to change, it descends the tree
(poplar, willow, or sallow) till it is within a few feet of the ground.
Then it commences gnawing away at the bark, at the same time cementing
all the pieces together with the gluey substance from its spinning
glands. In this way it surrounds itself with a very hard cocoon, which
so closely resembles the surrounding bark in colour that detection is
difficult indeed.
But how will the caterpillar proceed if it is removed from its native
tree and has no bark to gnaw? That you can easily answer for yourself,
or rather Puss will answer it for you. Go and search among the poplars,
willows and sallows in the month of July. You may possibly come across a
caterpillar that is just in the act of creeping down the bark in search
of a resting place; but if not you may be successful in obtaining a few
either by examining the twigs, or you may start them from their hiding
places by smartly tapping the smaller branches with a strong stick.
Having secured one or more larvae, take them home, and they will give
some rather novel performances. If they are not fully grown, you must
supply them with fresh leaves every day till they refuse to eat; and
then is the time for your experiments. Shut one in a little wooden box,
and you will have the pleasure of watching it construct a cocoon of
chips of wood that it has bitten out with its powerful jaws, all joined
together into a hard shell by means of transparent glue. Shut another
Puss in a glass vessel--a tumbler, for instance--either by placing it
under the inverted vessel, or by covering over the top. Perhaps it will
not be superfluous to mention that, should you place it under an
inverted vessel, this vessel should not stand on a polished table, for,
whatever be the material, unless _extremely_ hard, it is sure to be
utilised in the manufacture of the cocoon.
Let us suppose, then, that the caterpillar is under an inverted tumbler
that stands on a plate or saucer. Now it is for _you_ to decide what
material shall be used in the construction of the new home. Give Puss
some fine strips of brightly coloured ribbon, and it will construct a
very gaudy house by gluing them together. Or, provide it with sawdust,
pieces of rag, glass beads, sand, paper, anything in fact; and the
material will be 'made up' into a cocoon more or less ornamental
according to the nature of the supply.
But what if you give it _nothing_ with which to work, and so inclose it
that nothing its jaws can pierce is within its reach? For instance, shut
it in with tumbler and saucer as before, inverting the former on the
latter, and give it no material whatever. What will it do now? We will
watch and see.
At first it is very restless, and walks round and round the edge of the
tumbler, evidently a little dissatisfied with the prospects. Then, after
a little while, the events of nature transpiring in their fixed order
regardless of trivial mishaps, the glutinous fluid begins to flow from
the creature's spinning glands, and it moves about in a somewhat aimless
fashion, applying the transparent adhesive matter both to tumbler and
saucer.
It seems now to become a little more reconciled to its unnatural
surroundings; and, making the best of bad matters, keeps its body in one
place, and starts the construction of a ridge or barrier all round
itself. By the continued application of the creature's spinneret this
barrier is made gradually thicker and higher, till at last the
overhanging sides meet and the caterpillar is inclosed in its
self-constructed prison. But the walls of this prison are so transparent
that every movement can be watched; and, after the insect has spent a
few days in completing the cocoon, we can see it cast off its old skin,
and appear in the new garb of a fine greenish chrysalis.
Its soft green skin soon hardens and turns to a rich dark brown colour,
and it settles down for a long rest lasting till the following May or
June.
When the whole operation of building is completed, lift up the tumbler,
and up will come the saucer too. The two are firmly glued together by
the substance secreted; and the power of this as a cementing material
will be well illustrated if you endeavour by mere pulling force to
separate the two articles.
The Puss is not the only caterpillar that works up a foreign material
with the contents of the spinning organs. There are several others, in
fact, that use for this purpose fragments of wood or other parts of the
food plants; and a still larger number bind together leaves, fresh or
dead, or particles of earth or other matter. Several such cocoons will
be described in our accounts of individual species in another chapter.
We shall now devote a little space to a few general remarks on the
chrysalides and the final metamorphosis of butterflies and moths.
CHAPTER IV
_THE PUPA OR CHRYSALIS_
As soon as the last moult of the caterpillar is over, the chrysalis that
had already been developing under the cover of the old skin is exposed
to full view; and although the perfect insect is not to be liberated for
some time to come, yet some of its parts are apparently fully formed.
[Illustration: FIG. 30.--THE PUPA OF THE PRIVET HAWK (_Ligustri_).]
[Illustration: FIG. 31.--THE CHRYSALIS OF THE LARGE WHITE BUTTERFLY
(_Brassicae_).]
The newly exposed skin of the chrysalis is very soft and moist, but as
it hardens it forms a membranous or horny covering that protects and
holds firmly in place the trunk and the various limbs and appendages
that are distinctly to be traced on the under surface.
If, however, you examine a chrysalis directly after the moult is over,
you will often find that the wings, antennae, proboscis, and legs of the
future butterfly can be easily separated from the trunk of the body on
which they lie by means of a blunt needle, and can be spread out so as
to be quite free from that surface.
In form the chrysalides of butterflies and moths are as variable as the
caterpillars. Many of the former are sharply angular like that of the
'Small Tortoiseshell' already mentioned; but some of the
butterflies--the Skippers (page 197)--have smooth and tapering
chrysalides, and so have most of the moths.
In colour they are equally variable. Some are beautifully tinted with
delicate shades of green, some spotted on a light ground, some striped
with bands more or less gaudy and distinct, but the prevailing tint,
especially among the moths, is a reddish brown, often so deep that it is
almost a black.
[Illustration: FIG. 32.--THE PUPA OF THE DARK GREEN FRITILLARY
(_Aglaia_).]
[Illustration: FIG. 33.--THE PUPA OF THE BLACK-VEINED WHITE BUTTERFLY
(_Crataegi_).]
As a rule there is no marked resemblance between the different stages of
the same insect. Thus, a brilliantly coloured caterpillar may change to
a dull and unattractive chrysalis, from which may emerge a butterfly or
moth that partakes of the colours of neither. But in a few cases there
_are_ colours or other features that remain persistent throughout the
three stages, or show themselves prominently in two.
An interesting example in point is that of the Magpie or Currant Moth
(page 279). The caterpillar of this moth is cream-coloured, with orange
stripes along the sides, and very bold black markings down the back. The
chrysalis, which is at first entirely yellow, afterwards turns black
with the exception of some yellow transverse bands. Then, the moth
exhibits the same colours as these two earlier stages, with the same
degree of boldness; for its pale cream-coloured wings, tinted with
patches of yellow, are marked with numerous deep black spots. Thus, in
this case, we find the same general character of the colouring
throughout the insect's existence.
[Illustration: FIG. 34.--THE PUPA OF THE CURRANT MOTH.]
[Illustration: FIG. 35.--PUPA OF THE PALE TUSSOCK MOTH (_Pudibunda_).]
Another interesting example, though not so striking as the last, is to
be found in the case of a group of moths known as the _Liparidae_. The
caterpillars of these are remarkable for their very hairy bodies, often
ornamented by several bold brush-like tufts. The chrysalides are also
hairy; and several of the moths themselves are not only thickly clad
with shaggy hair, but a bold tuft often tips the abdomen.
We must not leave these few remarks on the characters of chrysalides
without a mention of the brilliant spots of burnished gold that decorate
the pupae of certain butterflies. This is the feature that led to the
invention of the term _chrysalis_, which is derived from the Greek word
_chrysos_, meaning _gold_. For the same reason the term _aurelia_ has
been applied to the pupae of _Lepidoptera_, this being derived from
_aurum_--the Latin name for gold.
Strictly, then, these two terms apply only to the pupae of a certain
number of the butterflies; but the former is now generally used to
designate the pupae of all the _Lepidoptera_, and is even extended to the
corresponding stages of insects of other orders.
If you examine one of these gold-speckled chrysalides, the brilliant
metallic lustre seems to belong to the outer surface, just as if certain
spots had been tipped with real gold; but after the butterfly has
quitted its case the beautiful golden spots are gone. This proves that
the metallic appearance is not due to reflection from the outer surface
of the chrysalis, but to a reflection from some structure beneath it.
This latter is a very thin membrane which lies just under the outer
transparent covering of the chrysalis.
The period during which the _Lepidoptera_ remain in the chrysalis state
varies very considerably in different species, and also depends more or
less on the temperature. As a rule, when a caterpillar pupates before
the end of the summer, it remains dormant in the pupal condition for
only a few weeks; but, if late in the summer or in the autumn, it
remains in this condition throughout the winter, and emerges in the
following spring or early summer.
Both these conditions are illustrated in the life history of the Large
White or Cabbage Butterfly--an insect with which we have already become
acquainted. We get two distinct broods of this butterfly every year, the
first appearing in May and the second in August. The eggs of the first
brood hatch in about a fortnight, and the larvae are full grown about
four weeks later. These then change to chrysalides, from which the
perfect insects (the second brood) emerge in a few weeks--the period
varying slightly with the temperature of the season. From the eggs of
this second brood we get another invading army of cabbage eaters that
change to pupae late in the summer. These remain dormant till the
following April, and may be found in numbers throughout the winter,
attached to the walls and fences of kitchen and market gardens.
If, then, the pupae of the same species are so influenced by the
temperatures of the seasons, can we limit or prolong the period of
quiescence by subjecting them to high or low temperatures artificially
produced? Most certainly we can; and every practical entomologist knows
how to obtain the perfect butterflies and moths of certain species long
before their appointed times, or, if he desires it, to compel them to
remain in their dormant stage long after the natural period has
terminated.
Sometimes an enthusiastic insect hunter obtains a large number of what
we may term 'winter pupae,' by collecting and breeding various species.
He also anticipates a number of successful captures of perfect insects
during the following summer. Thus, from two distinct sources, he obtains
a goodly assortment of butterflies and moths, the setting, preserving,
and arranging of which entails an immense amount of home work.
Under such circumstances he will sometimes endeavour to cause some of
his pupae to emerge before their accustomed time, so that he may get some
of his insects 'on the boards' before his field work is in full swing,
and so avoid a rush, or prevent the loss of insects that will be spoiled
before he has time to take them in hand.
This process of hurrying up his pupae he calls 'forcing,' and simply
consists in keeping them for a time in a warm room or hothouse where the
high temperature is pretty constant.
On the other hand, the entomologist may desire to try the effect of a
continued _low_ temperature on his pupae. This he can do by placing his
pupae in an ice house. Such experiments have often been performed, and
the results are very interesting. In some cases the emergence of the
perfect insect has been delayed for many months, and even years; and
then, after an exposure to a normal temperature lasting only a week or
two, the winged insect has made its appearance just as if nothing
unusual had happened.
Such are the effects of _extreme_ temperatures on the duration of the
chrysalis state; and we naturally infer, from such results, that the
pupa under natural conditions is influenced, though in a lesser degree,
by the variations experienced with the seasons, especially in such a
fickle climate as our own.
The insect hunter has always to bear this in mind, and particularly so
when he sets out on a search for certain desired species. Suppose, for
example, he has set his mind on the capture of a certain butterfly that
_usually_ appears in the _first_ week in May. Before finally naming the
day, he has to consider what the weather has been during the last few
weeks, and if he finds that this has been much warmer than the average
for the corresponding periods in the past, he selects a day in _April_,
earlier or later according to the difference between the present season
and the average.
If he does not pay due attention to such considerations, he will
sometimes find that all the insects netted are shabby and much worn,
even though, under average conditions, he would be catching newly
emerged and brilliant specimens. This, then, will explain how it is that
we so often see in entomologists' periodicals startling accounts of
'early captures,' and of the appearance of certain insects late in the
season that _ought_ not to have emerged till the following summer.
I will give just one illustration of these variations. The beautiful
Orange Tip Butterfly (Plate I, fig. 7) generally appears about the
middle of May in the southern counties. Farther north it is of course a
little later. In the north of England it has been taken in June; and in
Scotland as late as July. On the other hand, I have taken it in
Gloucestershire as early as March, on a rather bleak day with a cold
east wind; and, withal, in a field on the slope of the Cotswolds fully
exposed to the unfavourable breeze; but it was evident that, in this
case, the butterfly had been enticed from its winter quarters by the
milder weather of the few previous weeks.
It may be as well, in passing, to observe that it is not only the pupa
that is influenced by temperature. The hatching of eggs may be forced by
high temperatures, or be retarded by exposure to cold; and in nature the
period of incubation varies with the seasons. The larvae, too, grow
faster or more slowly, or pupate earlier or later from similar causes.
And so no very definite date or period can be assigned to any one stage
of any insect.
Now let us return to one of the chrysalides that we have already watched
through the earlier stages of its existence, and follow it in its future
development.
It is now, as we say, in its quiescent or dormant condition, but we must
not suppose that it is always in a profound sleep, nor can we say that
it is insensible to its surroundings. Touch it gently or surprise it
with a puff of air from your mouth, and it will begin to wag its pointed
tail, sometimes with such vigour as to send the body rolling round and
round in its box. Lay it on a bed of cocoa-nut fibre or finely sifted
soil and let it remain _quite undisturbed_ for a few hours or days, and
you will probably find that, by occasional movements of its body, it has
made a slight depression in its bed, and lies partly submerged. I have
known some chrysalides to completely bury themselves in this way during
the course of a day or two, and others to partly expose themselves after
having been lightly covered. Others again, I have observed, will move
smartly if a strong light is suddenly turned on them. Many, too,
certainly appear to have a strong objection to exposure to the direct
rays of a hot sun; for, when thus exposed, they will struggle
persistently, as if to work their bodies into some shady corner. I would
not advise a young entomologist to try this experiment, however, if he
values the pupae he possesses, for direct sunlight is undoubtedly very
harmful to many species, and perhaps it is to all.
Some chrysalides are not nearly so active as has just been represented;
in fact, there are many which seem to show no signs of life during the
greater part of the time spent in that state. But in all, whether
apparently active or not, certain important internal changes are at
work. We have already noticed that, even in the last days of the
_larval_ existence, some of the organs of the future imago are to be
traced. But these are as yet imperfectly developed. We have also
observed that a continuation of these changes, gradually carried on,
would be impossible in a voracious feeder; so the insect, now fully
grown, and no longer requiring a supply of food, settles down in perfect
quiet, submitting itself quite passively to any further changes that
nature may demand.
It has already suffered the loss of its claspers. Its wonderful jaws
that did so much damage (for good or evil as the case may be) to the
vegetable world are now gone, and the bulky digestive apparatus has
rapidly dwindled to useless dimensions. These and other changes, already
in progress, have to be perfected while the creature is in a restful and
helpless condition, though they may often be retarded or even suspended
during cold weather when progress would certainly bring it to an
untimely end.
But now the grandest of all these transformation scenes is nigh at hand.
The protective skin is already loosening from the almost perfect imago,
and consequently feels softer and far more yielding than it did when in
close contact with the body: the swaddled butterfly or moth (for such
the pupa is) is slowly preparing to throw off its imprisoning garb. The
wings and large compound eyes are assuming their final colours, which
now begin to show themselves through the more or less transparent skin,
and the long legs, the perfectly formed antennae, and the slender
proboscis, all of which are folded closely under the creature's thorax,
now begin to move within their loosened sheaths.
Now let us watch it closely, for one of the most wonderful sights ever
witnessed by a naturalist is about to be presented to our view. We think
we can observe slight movements; and, it may be, we can actually see the
struggling insect endeavouring to set itself free. The legs and
proboscis are moving within the loosened skin; and lo! as we watch these
motions, the prison wall bursts with a slight snapping noise (at least,
such is the case with some of the larger species), and in a moment out
pop a few long legs which immediately struggle for a foothold. The
proboscis also appears, alternately lengthening itself out and coiling
into a spiral, as if impatient to reach the sweet nectar from the bottom
of some fragrant flower cup.
[Illustration: FIG. 36--A BUTTERFLY, JUST AFTER EMERGING.]
All this takes place in less time than one requires to describe it; and,
before many seconds have passed, the struggling insect has quite
completed its last moult, and is bidding good-bye to the rent garment
that has done it good service for so long a time.
But how dreadfully disappointing! Did we not say only a few minutes
since, that a beautiful butterfly or moth was about to emerge? How,
then, is this? Here is an odd-looking creature, such as we have never
seen before! True, it has the right kind of body, though even that is so
soft and heavy that it is fairly dragged along as the insect walks. Its
antennae, too, seem to be just the right thing--that is, just what we
were expecting to see. But oh! the wings! Are we looking at a
deformity?--a failure on the part of Nature to produce what she ought?
We will not judge hastily, but continue to watch it a little longer. It
seems very restless at first, and, with the fluttering apologies for
wings, drags its heavy body along till it reaches some surface up which
it can climb. If nothing of the kind is close at hand you may place a
_rough_ upright stick in its path, and it will immediately begin to
ascend. Its motto is now 'Excelsior!' and its ambition to rise may be so
great that, on reaching the very top of the stick provided for it, it
struggles for a still higher position in life till, failing to get a
foothold in the air itself, it falls to the ground and has to retrace
its steps.
I once thought I would like to test the perseverance of a large moth in
performing its first upward journey; and as it was one from a chrysalis
to be found in nature at the foot of a tree that attains some
considerable height, I was, of course, prepared to exercise a little
patience myself.
As soon as the moth had emerged, I placed it at the bottom of a window
curtain that hung from about eight feet high to the floor. In less than
half a minute it had reached the top, and was struggling hard to get
still higher. I took it down, and again placed it at the bottom. Up it
went as fast as before; and this was repeated nine times with exactly
the same result. For the tenth time I placed the persevering creature at
the bottom of the curtain; and, after it had walked about halfway up, it
_suddenly_ stopped, apparently quite satisfied with having travelled a
distance of over seventy feet in an upward direction. Its six legs were
immediately arranged symmetrically in a business-like manner, and there
it settled quite still, as if it had some definite object in stopping
just exactly in that spot.
But we must now return to our own insect, which has by this time settled
itself in a similar manner on the stick we provided for it. The peculiar
organs which represent the wings, though so very small, show distinctly,
in miniature, the colour and pattern of the fully developed wings of the
species. An interesting change is just now commencing. These wings are
apparently growing larger, but the development is very unequal, so that
they become curled and crumpled till they are even more unsightly than
before. All seems to be going amiss. But this lasts only for a short
time. The fluid from the body steadily rushes into the _nervures_,
causing the wings to expand, and in a few minutes the beautiful pinions
are stretched to the full extent, assume their normal shape, and expose
the full glory of their brilliant colours.
It may be interesting if I give an example showing the exact time taken
for the full development of the wings of a certain insect. So I will
here quote an entry from my note book; and, by the way, let me strongly
advise all my young readers who follow up this subject to habitually
enter in a book kept specially for the purpose all facts which strike
them as they pursue their study of nature. The note to which I refer
runs as follows:
'Early on the evening of the 22nd [April] I selected a few chrysalides
of Populi [the Poplar Hawk Moth, page 209] which, from the looseness of
their cases, were thought to be just on the point of emerging. At 8.46
one of them showed signs of restlessness; and, after a few vigorous
movements, during which it rolled itself over on the glass [I had placed
the pupae on a piece of plate glass so that slight movements might be
more easily detected], the front of its case was suddenly thrust off
with considerable force; and in _less than four seconds_ the imago was
quite free and crawling on the table. After trying hard to reach a
higher point than was provided for about four minutes, it rested to
expand its wings--now about seven-sixteenths of an inch long, or
one-third the total length of the body. At 9 o'clock the wings reached
half the length of the body, and were much curled. At 9.12 they were
fully expanded and straightened out.'
From this extract we see that the whole period from the bursting of the
case to the full expansion of the wings was only twenty-six minutes; and
it will be well to remind the reader that the process occupies even a
much shorter time than this with many species, both of butterflies and
moths. It will be observed, also, that the _evening_ was chosen as the
time for the observation. There was a reason for this. The Poplar Hawk
Moth, as is the case with many others, almost invariably emerges from
the chrysalis in the evening--usually after dark. But it may be
mentioned in passing that a far larger number of the _Lepidoptera_ as
invariably emerge in the morning.
Again we will return to our newly emerged insect, for there are still
one or two interesting points to observe. The wings have fully expanded,
it is true, but how very limp they are! Take the creature on the tip of
your finger and hold it so that its body is in a horizontal position.
Immediately the wings bend downward with their own weight, so soft and
flexible are they. The body, too, is still very soft, and apparently
much too heavy for flight. Then, if you place it on a flat surface, it
will immediately try to find some perpendicular or overhanging surface
from which it can suspend itself by means of its legs, so that the
pendant and straightened wings are in the best possible position for
drying. As the insect walks away in search of such a resting place, the
body still drags as it did before, and the wings bend over, either both
on one side or one on each side of the body.
It is some time before the wings are sufficiently dry and rigid for
flight, but the period varies greatly with different species. Some of
the small butterflies and moths take to flight long before an hour has
passed, but in many cases several hours elapse before the creature
starts from its first resting place. Butterflies that emerge in the
morning spend their first day actively on the wing; but the nocturnal
moths that emerge early in the day do not fly till evening twilight.
When, however, the time arrives, the insect flutters its wings as if to
test their power before committing itself to the air; and frequently,
after only a few seconds spent in this preparatory exercise, off it
darts with astonishing rapidity. But others seem far more cautious. They
vibrate their wings, sometimes with such rapidity that they are lost in
a kind of mist, and with such power that their bodies would be carried
suddenly into the air were they not firmly anchored by three pairs of
hooked claws. Then, continuing the rapid vibration, they move slowly
along, always holding on firmly by one or more legs, as if to still
further satisfy themselves concerning the efficiency of their wings.
Then they venture on a few short trial trips from one neighbouring
object to another, and at last gain sufficient confidence for a long
voyage.
How strange must be the feelings of a winged insect during its first
flight! After a long period during which it was a helpless, crawling
grub, and this followed by a term of imprisonment during which it was
almost or quite shut off from the world, it now suddenly acquires such
great powers of locomotion that it is often a match for ourselves.
But, alas! this life is short. A few days spent in sporting with those
it meets and in sucking the sweet juices of many flowers; then a day or
two during which the female deposits its eggs; again a few days employed
in pleasures that become less and less attractive, till, at last, the
creature becomes weary of life and settles down to die.
We have now traced the complete life history of the _Lepidoptera_ from
the egg to the perfect insect, avoiding descriptions that apply only to
certain species as far as possible, excepting where such are useful as
illustrations.
Only one thing more remains to be done before we start in real earnest
with our practical work. We shall shortly be giving hints on the modes
of capture, the 'setting' and the preservation of butterflies and moths.
And in so doing we shall often have to observe important points in which
our dealings with these two great divisions of the order will differ
very materially. Hence we must not consider ourselves ready to proceed
with the practical portion of the entomologist's labours till we are
perfectly satisfied that we know the main features that enable us to
distinguish between the butterflies and the moths, and also know just a
little concerning the subdivisions on each side.
This, then, shall form the subject of the next short chapter.
CHAPTER V
_CLASSIFICATION OF THE LEPIDOPTERA_
The _Lepidoptera_ are divided into two very unequal groups, to which we
have so frequently alluded as 'Butterflies' and 'Moths.' And, although
these two terms are popularly applied in a fairly accurate manner, yet,
strange to say, very few persons indeed have any definite knowledge of
the differences that entomologists recognise between the two groups.
Every entomologist has his circle of sympathetic and, perhaps, even
admiring friends. Consequently, many a little package is sent round to
his abode 'with great care,' accompanied by a note or a message
concerning the fine 'butterfly I have just caught, and thought you would
like to add to your collection.'
The 'butterflies' that so frequently reach us through these channels
nearly always turn out to be _brightly coloured_ moths, and this
naturally gives one the idea that the popular notion as to the
classification of the _Lepidoptera_ is based on colour or brilliancy of
design, the term 'butterfly' being applied to the gayer species, and
'moth' to the more dingy members of the race.
There is really some shadow of a reason in this method of nomenclature,
for butterflies _are usually_ more brightly clad than moths; but the
scientific classification, at least as far as the main divisions and
subdivisions are concerned, has nothing whatever to do with colour or
design; and we must at once acquaint ourselves with the fact that there
_are_ very dingy butterflies, and most beautiful and highly coloured
moths.
How shall we account for the fact that the specimens so kindly sent us
by our friends are generally moths? Is it because moths are more
numerous and more frequently seen? They are certainly more numerous;
for, while our butterflies do not number seventy species, the other
division contains about two thousand. Yet, in spite of this fact, moths
are not generally observed as much as butterflies, for the former are
nearly all night-fliers, and the latter _always_ fly by day and rest by
night.
Still our question remains unanswered. The reason is this. The captives
sent us are seldom caught on the wing. Most of our grown-up friends,
even though they admire our own pluck and general carelessness
concerning the remarks of the spectators of our entomological antics,
would not themselves like to be seen, hat in hand, chasing a butterfly;
and the night-flying moths are, of course, less frequently observed. But
they often, in the course of their daily employments, meet with a large
moth fast asleep in some corner of a dwelling house, workshop, or
outhouse. Such moths are easily caught while in the midst of their
slumbers, and, as they often make no attempt to fly by day, are as
easily transferred to a box suitable for transmission by messenger or by
post.
In the above few remarks we have alluded to some features by which the
two great groups of the _Lepidoptera_ may be distinguished; but we have
already referred (page 5) to a far more important one in our description
of the various forms of antennae. All butterflies--at least all _British_
butterflies--have knobbed or clubbed antennae, while the corresponding
organs of all our moths terminate in a sharp point.
This distinction obtains in all British _Lepidoptera_, and is so far
regarded as the most important basis of classification that naturalists
have derived from it the two Greek terms that are synonymous with our
two popular names--butterflies and moths. The scientific name for the
former group is _Rhopalocera_--a term derived from two Greek words, one
signifying a horn, and the other a club, and thus meaning 'club-horned.'
The corresponding name for moths is _Heterocera_, derived from the same
source, and meaning 'variously horned.'
But, although we find embodied in these two long and formidable names an
unerring mark of distinction between British butterflies and moths, we
must not neglect other less important facts which, though less
distinctive, are not without interest.
Observe a butterfly at rest. Its wings are turned vertically over its
back, and brought so closely together that they often touch. In this
position the 'upper' surfaces of the 'upper' wings are completely hidden
from view, and the 'under' surfaces are exposed on the two sides,
except that those of the 'upper' pair are partly hidden by the other
pair.
Now look at a moth under the same circumstances, and you will generally
find the wings lying over its body, which is almost or completely hidden
beneath them. As a rule the upper pair together form a triangular
figure, and entirely cover the second pair; but in some cases a portion
of each of the under wings extends beyond the margin of those above
them, and in others the upper pair extend so far forward that nearly the
whole of the under wings is exposed behind them.
[Illustration: FIG. 37.--A BUTTERFLY AT REST (LARGE COPPER).]
[Illustration: FIG. 38.--A MOTH AT REST (GOTHIC).]
Again, the wings of butterflies are so rigid that they can never be
folded; but you will observe that the under wings of moths are generally
very thin, soft, and pliant, and are neatly pleated lengthwise when not
in use.
Another feature deserving notice is a slight difference to be often
observed in the form of the body. The butterfly, which generally has a
slender body, has a distinct constriction or waist between the thorax
and abdomen. This is not so apparent with moths, and especially with the
thick-bodied species.
The _Rhopalocera_ or Butterflies are divided into _Families_, each of
which contains insects that possess certain features in common by which
they may all be distinguished from the members of any other family.
The British species represent eight families. They are as follows:
1. _Papilionidae._--Containing only one British species--the beautiful
Swallow-tail (Plate I, fig. 1).
2. _Pieridae._--Containing ten species. These are often known
collectively as the 'Whites,' but include four butterflies that are
distinguished by beautiful shades of yellow and orange.
3. _Nymphalidae._--This family contains seventeen insects, among them
being several splendid species. It includes the Fritillaries and
Vanessas.
4. _Apaturidae._--Of this we have only one representative--the Purple
Emperor (Plate V, fig. 1).
5. _Satyridae._--Including the 'Browns' and 'Heaths,' and numbering
eleven species.
6. _Lycaenidae._--Including the Hairstreaks, 'Coppers,' and 'Blues,' in
all seventeen species.
7. _Erycinidae._--Containing only the 'Duke of Burgundy.'
8. _Hesperiidae._--This family contains seven British butterflies
commonly known as the 'Skippers.'
Although all the members of the same family resemble each other in
certain points of structure, or in their habits, yet we can often find
among them a smaller group differing from all the others in one or two
minor particulars. Such smaller groups are called _Genera_.
To make this all quite clear we will take an example.
The Brimstone Butterfly (Plate II, fig. 4) belongs to the second
family--_Pieridae_, _all_ the members of which are distinguished from
those of the other families by the characteristics mentioned on page
141.
But our Brimstone Butterfly possesses another very prominent feature in
which it differs from all the other British _Pieridae_, and that is the
conspicuous projecting angles of both fore and hind wings. Among the
foreign species of the family we are considering there are several that
possess these angles; but as there are no others among our own members,
the 'Brimstone' is placed by itself in the list of British _Lepidoptera_
as the only member of the genus _Gonopteryx_ or 'angle-winged'
butterflies.
Thus the full relationship of this butterfly to other insects may be
shown in the following manner:
_The Brimstone Butterfly._
=ORDER.=--_Lepidoptera_
=Section.=--_Rhopalocera_
FAMILY.--_Pieridae_
_Genus._--_Gonopteryx_
Species.--_Rhamni_
Now, every butterfly has a Latin or Greek name in addition to that by
which it is popularly known. I should have said _two_ Latin or Greek
names. The first of these is always the _generic_ name, and the second
is the one by which we denote the particular member or _species_ of that
genus. Thus, the scientific name of the Brimstone Butterfly is
_Gonopteryx Rhamni_.
'But,' the reader may be inclined to ask, 'why should we not be
satisfied with the one popular name only?' And, 'If we _must_ have a
separate scientific name, could we not find suitable terms among our
English words to build up such a name--one that might express the
principal characteristics of the insect, and also serve all the purposes
of classification?'
Such questions sound very reasonable, and so they are. But the
entomologist's answer is this. We ourselves may get on well without the
help of the dead languages, but we have brother naturalists all over the
world, speaking a great variety of different languages. We endeavour to
help one another--to exchange notes and generally to assist one another
in our labours; and this can be greatly facilitated if we all adopt the
same system of nomenclature. The educated of most of the great nations
generally know something of Latin and Greek, and consequently the
adoption of these languages is generally acceptable to all.
This sounds well, but for my own part I believe that if we are to make
any branch of natural history a popular study, especially with the
young, we must to a certain extent avoid anything that may prove
distasteful. There is no doubt whatever that many a youngster has been
turned away from the pursuit of the study of nature by the formidable
array of almost unpronounceable names that stretch nearly halfway across
a page; and those who desire to make such a study pleasant to beginners
should be very cautious with the use of these necessary evils. One would
think, on glancing over some of the scientific manuals that are written
'especially for the young,' that the authors considered our own too mean
a language for so exalted a purpose, for in such works we find all or
nearly all the popular names by which the schoolboy knows certain
creatures he has seen entirely omitted, and the description of a species
appended to a long Latin term that conveys no idea whatever to the
reader, who is studying the description of a well-known animal or plant
and doesn't know it.
Our plan will be to give the popular names throughout, except in the
case of those few species that are not so well known as to have
received one; but the scientific names will always be given as well for
the benefit of those readers who would like to know them. And the short
description of the method of classification just given will enable the
more ambitious of my readers to thoroughly understand the table of
British butterflies and moths toward the end of the book.
This table includes _all_ the British species of butterflies and of the
larger moths; and the arrangement is such as to show clearly the
divisions into sections, families, &c. It will therefore be of great
value for reference, and as a guide for the arrangement of the specimens
in the cabinet.
In the foregoing description of the method of classification butterflies
only are mentioned; but the division and arrangement of moths is carried
out in just the same manner except that the system is a little more
complicated. The number of moths is so large in comparison, that we are
able to select from them some very large groups the species of which
possess features in common. These groups are termed _tribes_, and are
again divided into families just like the butterflies. Thus the
arrangement of moths includes _tribes_, _families_, _genera_ and
_species_. We will take an example by way of illustration as we did
before, and ask the reader to verify the same by comparison with our
table:
_Example._--The 'Common Tiger' (Plate X, fig. 3).
=ORDER.=--_Lepidoptera_
=Section.=--_Heterocera_
TRIBE.--_Bombyces_
FAMILY.--_Cheloniidae_
_Genus._--_Arctia_
Species.--_Caia_
Scientific Name.--_Arctia Caia._
I have already said that the Latin and Greek names of butterflies and
moths are not at all necessary to the young entomologist. It is quite
possible to be well acquainted with the natural history of these
creatures, and to derive all the pleasure and benefits that the study of
them can afford without the knowledge of such names; but most
entomologists go in for them, often to the entire exclusion of the
popular English terms.
There are those who consider themselves (or would have us consider them)
expert entomologists because they have the power to vomit forth a long
list of scientific names of butterflies and moths which (to them) have
no meaning whatever; and it is astonishing that we meet with so many
youngsters who can rattle away such terms, and, at the same time, are
totally ignorant of the real nature of the creatures they name.
If you wish to be a naturalist in the true sense of the term, study your
_specimens_, and take but little pains to commit their hard names to
memory; and you will then find that the latter will gradually become
your own property without any special effort on your part. Your
continued reference to illustrated works and museum collections will
bring them to you almost unconsciously, and you will generally find your
entomological vocabulary extending as rapidly as your cabinet becomes
filled.
Again, with regard to the _meanings_ of the scientific terms, don't
trouble much about them. It unfortunately happens that in a very large
number of cases these names are ill chosen, and do not in any way refer
to the distinguishing characteristics of the species to which they are
applied. You will observe, too, if you look at the table, that many
insects have _two_ scientific names applied to the species, one being
placed in brackets after the other. In such cases both these names are
in common use, having both been applied by independent authorities, and
the insertion of the two will prove an assistance at times.
It is a common practice with entomologists, in their communications, to
use only the second or _specific_ name of insects. Thus, they would
speak of the Brimstone Butterfly as _Rhamni_, and not _Gonopteryx
Rhamni_. When _writing_ a communication, however, they very commonly
place in front of the specific name the initial letter of the first or
_generic_ name. Thus the full title of the butterfly just mentioned
would be abbreviated to _G. Rhamni_.
Having said so much concerning the principles of classification and
nomenclature, we will pass on to the practical portion of the
entomologist's work.
PART II
WORK AT HOME AND IN THE FIELD