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How to know the butterflies;a manual of

3 1924 022 557 353

DATE DUE

The original of this book is in the Cornell University Library.

There are no known copyright restrictions in the United States on the use of the text.

http://www.archive.org/details/cu31924022557353

HOW TO KNOW THE BUTTERFLIES

Plate I

PLATE I Frontispiece

TRANSFORMATIONS OF THE MONARCH (See page 204)

Fig. i. Full-grown larva.

2. Larva preparing to transform.

3. Chrysalis.

4. Empty chrysalis skin and butterfly.

(From photographs by Professor M. V. Slingerland, colored by Mrs. Slingerland.)

HOW TO KNOW THE BUTTERFLIES

A MANUAL OF THE BUTTERFLIES OF THE EASTERN UNITED STATES

BY

JOHN HENRY COMSTOCK

PROFESSOR OF ENTOMOLOGY IN CORNELL UNIVERSITY AND

ANNA BOTSFORD COMSTOCK

LECTURER IN NATURE STUDY IN CORNELL UNIVERSITY

WITH FORTY-FIVE FULL-PAGE PLATES FROM LIFE REPRODUCING THE INSECTS IN NATURAL COLORS

laboratory Bf Ornithotegy J59 Sapsucktr Woods Rottf Cornell University tttiact, New York 14850

D. APPLETON AND COMPANY NEW YORK -...- MCMIV

Copyright, 1904, by D. APPLETON AND COMPANY

Published May, )00i

TO

SAMUEL HUBBARD SCUDDER

CONTENTS

List of Plates

PAGE

ix

PART I

GENERAL ACCOUNT OF BUTTERFLIES I. The relation of Butterflies to other In-

sects

II. The Structure of Butterflies .

III. The Clothing of Butterflies

IV. The Metamorphoses of Butterflies . V. The Study of the Life of Butterflies

PART II

THE CLASSIFICATION OF BUTTERFLIES

3 1 6

20 25

Family I.

The Parnassians

35

. 42

II.

The Swallow-tails

45

" III.

The Pierids ....

. . . 69

" IV.

The Nymphs .... vii

. 102

CONTENTS

Family V. The Meadow-browns . " VI. The Heliconians . " VII. The Milkweed Butterflies " VIII. The Long-beaks . " IX. The Metal-marks " X. The Gossamer-winged Butterflies

PACE I 80

201

204 2IO 213

215

PART III

THE SKIPPERS

Superfamily Hesperioidea . Family I. The Giant Skippers . " II. The Common Skippers

Index

256 258 260

3°3

Vlll

LIST OF PLATES

FACING PLATE PAGE

I. Transformations of the Monarch . Frontispiece

II. The change from a Caterpillar to a Chrysalis

III. The first three stages of a Butterfly

IV. Parnassians and Papilio .... V. The Zebra Swallow-tail .....

VI. The Tiger Swallow-tail .....

VII. Swallow-tail Butterflies

VIII. Transformations of the Giant Swallow-tail .

IX. The Green-clouded Swallow-tail

X. The Black Swallow-tail

XI. Transformation of the Black Swallow-tail

XII. The Blue Swallow-tail .....

XIII. The Whites and the Olympia Orange-tip

XIV. The Whites

XV. The Orange-tips and the Yellows .

XVI. The Larger Yellows .....

XVII. The Yellows

XVIII. Fritillaries

XIX. The Diana Fritillary

XX. The Regal Fritillary

XXI. The Three Eastern Argynnids

XXII. The Smaller Fritillaries and the Crescent-spots

XXIII. The Angle-wings

XXIV. The Angle-wings

ix

20 24

4- 52 56 58 60 62 64

66

72

76

86

88

92

108

no

1 12

114

122

'34 140

LIST OF PLATES

PLATE

XXV.

XXVI.

XXVII.

XXVIII.

XXIX.

XXX.

XXXI.

XXXII.

XXXIII.

XXXIV.

XXXV.

XXXVI.

XXXVII.

XXXVIII.

XXXIX.

XL.

XLI.

XLII.

XLIII.

XLIV.

XLV.

FACING PAGE

The Mourning-cloak

The Vanessas ....

The Purples ....

The Monarchs and their Mimics

The Emperors ....

The Meadow-browns

The Meadow-browns

The Zebra and the Milkweed Butterflies

Metal-marks and Hair-streaks

Hair-streaks

Hair-streaks

The Coppers

The Blues

The Spring Azure

Skippers with a Brand and their Allies

Skippers with a Brand and their Allies

Skippers with a Brand and their Allies

Skippers with a Brand and their Allies

The Silver-spotted Skipper

Skippers with a Costal Fold and their Allies

Skippers with a Costal Fold and their Allies

154 166

170

174 184 190 204 220 226 232 236 246 250 270 276 280 284 -94 296 298

INTRODUCTION

There are many students of Nature who know the more common birds and flowers ; but our experience as teachers has convinced us that there are comparatively few that know the com- mon butterflies. This fact seems remarkable when we consider the abundance of butterflies and their attractive features ; and it can not be due to an unwillingness on the part of students to study these creatures. The reason for this condi- tion must be a lack of suitable aids to beginners in this study.

The literature treating of American butterflies is a very rich one ; it includes large, scholarly works with magnificent illustrations, and a con- siderable number of smaller manuals. But we believe that there is a field for still another book on this subject ; one that is richly illustrated without a confusing array of figures of species from remote parts of our country ; one with brief descriptions of species but sufficiently full so that the reader can definitely determine the species studied and one that shall give the more impor-

xi

HOW TO KNOW THE BUTTERFLIES

tant facts of the lives of our butterflies. It is with the hope of meeting this need that this book has been written.

It is hoped that the work will be of use to students in all parts of our country ; but in order that it may be of moderate size, the descriptions of species, with few important exceptions, have been restricted to those that occur in the eastern half of the United States. Many of these spe- cies, however, have a much wider distribution, some extending to the Pacific Coast.

XII

HOW TO KNOW THE BUTTERFLIES

PART I

GENERAL ACCOUNT OF BUTTERFLIES

I. THE RELATION OF BUTTERFLIES TO OTHER INSECTS

Butterflies belong to a class of animals, the Insects, that far outnumbers in species all other classes of animals taken together. The members of this vast assemblage of species agree, however, in the more general features of the structure of their bodies.

In all insects the body is composed of a series of segments or rings ; these segments are most easily seen in the hind part of the body (Fig. i). The segmented condition of the body is also characteristic of certain other animals, as the mil- lipedes, centipedes, lobsters, and others ; but in- sects can be distinguished from all of these by the following combination of characteristics : they breathe by means of a system of air tubes or

i

HOW TO KNOW THE BUTTERFLIES

trachea; opening through the sides of the seg- ments ; the body-segments are grouped into three

Fig. i. A butterfly showing the segmented condition of the abdomen.

regions, the head, the thorax, and the abdomen (Fig. 2) ; they have one pair of antenna; ; they have three and only three pairs of legs ; and in the adult state they usually have one or two pairs

of wings.

The class of insects is known to the zool- ogists as the class Hcx- aftoda, a name suggested by the six-footed con- dition of these crea- tures.

The class Hexapoda is divided into several orders ; thus the beetles constitute the order Coleoptcra ; the two-winged flies, the order Dip-

Fig. 2. A wasp showing the divi- sion of the body into head, thorax, and abdomen.

GENERAL ACCOUNT OF BUTTERFLIES

lera ; and the dragon-flies and damsel-flies, the order Odonata. Sixteen of these orders are commonly recognized.

The moths or " millers," the skippers, and the butterflies constitute the order Lcpidoptera. The members of this order have four wings, which are membranous and covered with over- lapping scales ; the mouth-parts are formed for sucking; and in the course of their development they undergo what is known as a complete meta- morphosis.

II. THE STRUCTURE OF BUTTERFLIES

The body of a butterfly consists of three regions, which are known as the head, the thorax, and the abdomen. The head is the first of the three regions ; the thorax, the intermediate ; and the abdomen, the last.

The head bears the eyes, the antennse, and the mouth-parts.

The eyes are two in number, one on each side of the head. They are easily recognized by their position and hemispherical form. But when they are examined with a lens they present a very different appearance than do the eyes of man ; each eye being composed of a large num- ber of little eyes, or ommatidia as they are

3

HOW TO KNOW THE BUTTERFLIES

termed. As the ommatidia are closely massed together, the outer surfaces of each is hexagonal in outline like the cells of honeycomb (Fig. 3). Eyes of this type are termed compound.

Many insects have simple eyes, or ocelli, in addition to compound eyes ; but ocelli are very rarely found in butterflies.

The antennce are the long, more or less thread- like appendages that project from the upper part of the head ; they are what children are apt to call the horns of the butterfly. Each antenna consists of many segments or ringlike divisions. The antennas are supposed to bear the organs of smell. In

Fig. 3. Part of a com-

pound eye, greatly butterflies the terminal seg- magmfied. ments of the antennas are en-

larged so as to form a club.

The mouth-parts of butterflies consist chiefly of a pair of palpi and the sucking organs, max- illa. The palpi are the jointed organs that pro- ject forward from the lower side of the head. They vary greatly in length in different families, and vary in the relative length of their segments, so that use is made of them in the classification of butterflies. The maxillae are greatly modified jaws, which are so lengthened that they have lost

4

GENERAL ACCOUNT OF BUTTERFLIES

all resemblance to the jaws of biting insects. Each maxilla is furnished with a groove, and the two maxillae are so fastened together that the two grooves form a tube through which liquid food is sucked. When not in use, the maxillae are coiled between the palpi.

The thorax bears the organs of locomotion, the legs and the wings.

The legs are six in number. Each leg con- sists of a series of segments. The basal segment, that by which the leg is attached to the body, is the coxa ; next is a small segment, the tro- chanter; then follows the principal segment of the leg, the femur; the next approaches the femur in size, and is the tibia ; the remaining segments constitute the foot or tarsus. The last segment of the tarsus usually bears a pair of claws.

The wings are four in number and are always present in adult butterflies. In many species of moths the wings are wanting in one sex ; but this is true of no butterfly.

In the study of the classification of butterflies much use is made of the variations in the struc- ture of the wings. This is also true in the study of any of the groups of winged insects ; but in the Lepidoptera, where the body is covered with

5

HOW TO KNOW THE BUTTERFLIES

a dense clothing of scales which hides from view most of the distinguishing characteristics used in the classification of beetles and other compara- tively naked insects, the structure of the wings presents an even larger proportion of the easily available criteria for separating the order into its subdivisions.

It is essential, therefore, that the student of butterflies should learn at the outset the more im- portant facts regarding the structure of the wings, and become familiar with the terms that have been applied to the different parts of a wing. Fortunately it is an easy matter to do this.

The two pairs of wings are designated as the fore wings and the hind wings respectively. Some writers on butterflies term the fore wines the primaries, and the hind wings the secondaries.

The wings are more or less triangular in out- line ; a wing, therefore, presents three margins : the costal margin, or casta (Fig. 4, a— 8) ; the outer margin (Fig. 4, b-c) ; and the inner margin (Fig. 4, c-d).

The angles limiting these margins have also received names. The angle at the base of the costal margin (Fig. 4, a) is the humeral angle ; that between the costal margin and the outer margin (Fig. 4, b) is the apex of the wing ; and

6

GENERAL ACCOUNT OF BUTTERFLIES

the angle between the outer margin and the inner margin (Fig. 4, c) is the anal angle.

The wings are large membranous appendages, which are thickened along certain lines. These thickened lines are termed the veins of the wing; and their arrangement is de- scribed as the venation of the wings.

A study of the wings of all orders of winged insects has shown that there is a striking uniformity in the more general features of the venation of the wings of the more generalized or "lower" members of the different orders; while in the more specialized or "higher" members of each order this generalized type of venation is more or less modified.

An investigation of the various ways in which this generalized type of wing venation has been modified and of the varying degrees of these modifications has contributed much to our knowl- edge of the relationships of the different groups of insects.

Fig.

4. Margins and an- gles of a wing.

HOW TO KNOW THE BUTTERFLIES

These studies have shown that all winged in- sects have doubtless descended from a common winged ancestor. And although we do not know the exact form of this primitive winged insect, which lived during the Silurian age, we may infer that those structural features that are common to the generalized members of the different orders of winged insects have been inherited from this common ancestor.

The features of the wing-venation which are commonly present with the generalized members of the different orders of winged insects, and which we therefore infer were possessed by the primitive winged insect, are represented in Figure 5. From this hypothetical primitive type of wing-venation there can be derived, by methods of modification of which we have many illustra- tions among living insects, all the forms of vena- tion of insect wings known.

The venation of the wings of butterflies is one of the more specialized types of wing-venation, and one which can not be understood by the study of the wings of butterflies alone. It is necessary, therefore, to lead up to the explanation of this type by describing more simple or less modified types. We will describe first the hypothetical primitive type and then point out the ways in

8

GENERAL ACCOUNT OF BUTTERFLIES

which this type has been modified in the Lepi- doptera.

Taking the hypothetical type (Fig. 5) as an illustration, we see that the veins of the wings can be grouped under two heads : first, longitudi- nal veins, those that normally extend lengthwise of the wing ; and second, cross-veins, those that

3d A

2d A

Fig. 5. Hypothetical venation of the primitive winged insect

extend transversely from one longitudinal vein to another.

The names that have been applied to the longi- tudinal veins, beginning with the one nearest the costal margin of the wing, are casta, subcosta, ra- dius, media, cubitus, first anal, second anal, and third anal. In descriptions these veins are often designated, as they are in Figure 5, by the follow- ing abbreviations of these names : C, Sc, R, M, Cu, 1st A, 2d A, and 3d A.

Beginning with subcosta, the four veins that

9

HOW TO KNOW THE BUTTERFLIES

traverse the middle portion of the wing are branched; the subcosta divides into two branches, the radius into five, the media into four, and the cubitus into two. In this primitive type the costa and the three anal veins are not branched.

In designating the branches of a forked vein they are numbered, beginning with the one near- est the costal margin of the wing. Thus, the first branch of radius is designated as radius-one ; and for this term the abbreviation Rj is used.

In some insects there are very many cross- veins, but it is believed that the greater number of these have been developed secondarily. There are, however, a few cross-veins that are so con- stantly present among generalized insects that we feel warranted in believing that they were pres- ent in the wings of the primitive winged insect. These are represented in Figure 5, and are desig- nated as the humeral cross-vein (Fig. 5, Ji) ; the radio-medial cross-vein (Fig. 5, r~m) ; the medial cross-vein (Fig. 5, m); and the medio-cubital cross- vein (Fig. 5, m-cti).

In Figure 6 is represented the venation of the wings of Stkenopis, a moth, which is one of the most generalized of the living Lepidoptera. Here is found quite a close agreement in venation with

10

GENERAL ACCOUNT OF BUTTERFLIES

that of the hypothetical type. The more impor- tant modifications are the following :

The costa forms the costal border of the wing, and does not appear as a distinct vein. This is the case with nearly all insects ; but in many pu- pae the costa is distinct, and it is only in the later

h-c.o-

Fig. 6. Venation of the wings of Sthenopis.

stages of the development of the wings that it coincides with the costal margin.

In the hind wings, veins M4 and Cut unite for a short distance, and then separate ; in the fore winar these veins unite and remain united through- out the remainder of their length (Fig. 6, M4 -f-

Cu,).

ii

HOW TO KNOW THE BUTTERFLIES

It is only in a very few Lepidoptera that there is any indication of the existence of vein M4. In nearly all moths and in all butterflies media ap- pears to be only three-branched ; and it is custom- ary to regard the vein labeled M4 4- Cu, in the above figure as merely cubitus-one. For the sake of simplicity this course is followed in this work.

The most striking modification of the primi- tive type that has taken place in the wings of butterflies is the loss of the main stem of media and the joining of the branches of media to the veins on either side. Thus vein M, appears to be a branch of radius ; vein M3 , of cubitus ; and vein M2 is sometimes joined to radius and some- times to cubitus. That this change has taken place is easily seen by comparing the venation of StJienopis (Fig. 6) with that of the various but- terflies figured here.

Not only has the main stem of media been lost, but in nearly all wings of butterflies one or two of the three anal veins have disappeared. A care- ful study has shown that in the reduction of anal veins in the Lepidoptera the first anal vein is the first to disappear, and the third anal vein is the next to go.

The number of the branches of a branched vein is often reduced by the growing together, or

12

GENERAL ACCOUNT OF BUTTERFLIES

coalescence, of adjacent veins. Thus in many but- terflies radius of the fore wings instead of being five-branched is only four-branched or even three- branched (Fig. 7). In a case of this kind the designation R4+5 indicates that veins R4 and R5 have grown together to form a single vein.

In the hind wings of all butterflies the radius differs greatly from that of the fore wings. By referring to the venation of Sthenopis (Fig. 6) it can be seen that at the first forking of radius the vein is divided into two un- equal parts ; one of these is vein R„ the other gives rise to the remaining four branches of radius. This second part is termed the radial sector, and is labeled Rs in the figures. In all butterflies the branches of the radial sector of the hind wings all coalesce so as to form a single vein, and vein R, coalesces with the subcosta. This is well shown in the hind wing of Papilio (Fig. 8). It will be ob- served that in this wing vein RT soon after its separation from vein Rs joins vein Sc and the

13

Fig. 7. Venation of the wings of a metal-mark.

HOW TO KNOW THE BUTTERFLIES

two extend to the margin of the wing as a single vein, which for this reason is marked Sc-f-R,. It will also be seen that the radial sector extends to the margin of the wing as an unbranched vein,

marked Rs.

In some butter- flies a short spur extends from the subcosta near the humeral angle of the wing ; such a spur is termed the humeral vein (Fig. 7, H).

The thin spaces of thewings which are bounded by the veins are called cells. In descrip- tions of wings, es- pecially in indicat- ing the location of markings, it is often desirable to refer to one or more cells. It is necessary, there- fore, to have a nomenclature of the cells of the wing, as well as of the wing-veins.

14

Fig. 8.

-Venation of the wings of swallow-tail.

GENERAL ACCOUNT OF BUTTERFLIES

Having named the wing-veins, the simplest possible method of designating the cells of the wing is to apply to each the abbreviation of the name of the vein that forms its front margin. In Figure 9 the veins are designated by letters at the margin of the figure ; the cells by letters within the figure or at the ends of the dotted lines.

Near the center of the basal half of the wing there is a large cell which is bounded in front by the main «, stem of radius and which for this reason might be called cell R. But this cell is really composed of

tWO Cells, Which have FlG- 9— Fore wing of a butterfly with

the veins and cells named.

been thrown together

by the fading out of the main stem of media. For this reason this cell is designated as cell R -f- M. This is the discal cell of most writers on the Lepidoptera.

The details of the venation of the wings can be seen best, in Lepidoptera, on the lower sur- face of the wings ; as on this surface the veins are not so obscured by scales as on the upper

15

HOW TO KNOW THE BUTTERFLIES

surface. If necessary the scales can be removed from a small part of a wing with a small brush in order to expose the veins. A drop of chloro- form applied to a wing causes the veins to be more prominent for a moment ; the chloroform soon evaporates and leaves the wing uninjured.

At the base of each fore wing there is a prom- inent scalelike appendage ; these are known as the patagia.

The third and last region of the body, the ab- domen, requires little discussion in this place. It consists of several ringlike segments, and bears appendages at the caudal end connected with the organs of reproduction. The forms of these ap- pendages vary greatly in the different species, consequently much attention is devoted to them in the more technical works.

III. THE CLOTHING OF BUTTERFLIES

Every country lad knows that if a butterfly be handled there comes off from it upon the fingers a dustlike substance ; this is the clothing of the butterfly. If this dust is examined with a microscope each particle is seen to be of regular form, although a wide range of forms may be obtained from a single butterfly. The form that is most abundant on the wings is a flattened

16

GENERAL ACCOUNT OF BUTTERFLIES

scale, beautifully ribbed, with a series of project- ing teeth at one end, and a single pedicel at the other (Fig. 10).

If a piece of a wing of a butterfly be ex- amined with a microscope, it will be seen that these scales are arranged in regular, overlapping rows ; the arrangement being as regular as that of the scales on a fish or of the shingles on a

Fig. io. A series of scales taken from the body and wings of a single moth. (From Kellogg.)

roof (Fig. n). In the upper part of the figure the membrane of the wing is represented with the scales removed.

The scales of butterflies are modified hairs. That is, they are hairs which, instead of growing long and slender as hairs usually do, remain

17

HOW TO KNOW THE BUTTERFLIES

short, but grow very wide as compared with their length. Every gradation in form can be found from the ordinary hairlike form, which occurs most abundantly upon the body, to the short and broad scale, which is best seen upon the wings (Fig. 10).

The use of the scales on the wings is to strengthen them. We thus see that the wings

of these insects are fur- nished with much fewer cross-veins than are the wings of similar size in other orders. A sec- ondary use of these scales is that of orna- mentation; for the beautiful colors and markings of these in- sects are due entirely to the scales, and are destroyed when the scales are removed. Upon the body, legs, and other ap- pendages, the scales and hairs doubtless serve to protect the insect, being a sort of armor.

In the wings of males of many butterflies there are scent glands that open through scales. It should be stated in this connection that scales, like other hairs of insects, are hollow and well

iS

Fig. ii. Part of the wing of a butterfly, greatly magnified.

GENERAL ACCOUNT OF BUTTERFLIES

fitted to be the outlets of glands. The odor emitted by these scent-glands is supposed to attract the females ; as do the bright plumage and the songs of male birds.

To these scales, characteristic of the males, has been applied the name androconia (an-dro- co'ni-a), a word signify- ing male dust.

Androconia are of re- markable and various forms. "Among the Nymphalidae the andro- conia are usually long, slender, and feathered at the tip (Fig. 12, a); in the Pieridas they are usually fringed at the apex and heart-shaped at the base, the pedicel being peculiarly devel- oped into a slender stem with a ball at its tip (Fig. 12, 6) ; in the Lycasnidas a battledore shape is presented, the scale usually being quite small (Fig. 12, c). The androconia are found almost without exception on the upper side of the wings, and are more commonly met with on the fore wings than on the hind wings. They are often

19

Fig. 12. Androconia from the wings of male butterflies.

HOW TO KNOW THE BUTTERFLIES

found in certain limited spots or in folds of the wings." (Kellogg.)

The most familiar illustrations of the group- ing of the androconia in distinct patches are in the "brands" of the males of certain skippers, and in the discal patch of the fore wings of hair- streaks. It is among the skippers also that we find the most striking examples of folds formed for containing androconia, i. e., in the skippers with a costal fold. In the milkweed butterflies the androconia are in a little pocket close to vein Cu2 of the hind wings (see Plate xxxii.)

In caterpillars the fine hairs scattered over the surface of the body are sense-organs and are prob- ably tactile ; and it is believed that the organs of taste and of smell of insects are modified hairs. We thus see that the clothing of these insects serves many and widely different uses.

IV. THE METAMORPHOSES OF BUTTERFLIES

A butterfly in the course of its existence ap- pears under four distinct forms ; these are the eesr the larva or caterpillar, the pupa or chrysalis, and the adult.

The eggs are small, and consequently are rarely seen except by those who observe very closely. They are attached by the parent butter-

20

PLATE II

THE CHANGE FROM A CATERPILLAR TO A CHRYSALIS Fig.

i. Larva of the Mourning-cloak Butterfly fastened to a twig, ready to transform. Note the button of silk to which it is fastened. (Figure enlarged.)

2. Chrysalis just before freeing itself from its larval skin. (Figure enlarged.)

(From photographs by Professor M. V. Slingerland, colored by Mrs. Slingerland.)

Plate II.

GENERAL ACCOUNT OF BUTTERFLIES

fly to the particular kind of plant upon which the larva feeds. The eggs may have smooth oval shells ; but often the shells are beautifully ribbed and pitted (Plate III, Fig. i; Plate XXV, Fig. i); sometimes they are ornamented with spines, and frequently they are exquisitely col- ored.

When the young butterfly emerges from the egg it is what is known as a larva. This is a general term applied to the corresponding stage of all insects that appear under four distinct forms in the course of their development. Usually the larvae of butterflies and moths are called cater- pillars ; both terms are used in the following pages.

Caterpillars vary greatly in appearance ; but they are long, more or less wormlike in form. This fact has suggested the common names of many species ; thus the cabbage-worm and the tomato-worm are caterpillars ; the former is the larva of a butterfly, the latter develops into a moth.

There is no characteristic by which we can distinguish the larvae of butterflies from those of moths ; but with a little experience the student can learn to recognize the larvae of our larger and more common butterflies. 3 21

HOW TO KNOW THE BUTTERFLIES

In the caterpillar state the division of the body into three regions is not so well marked as it is with the adult butterfly. The head is always distinct ; following the head there are thirteen comparatively similar segments, which constitute the thorax and the abdomen. The first three seg- ments following the head form the thorax of the adult insect ; each of these segments bears a pair of legs, which develop into the legs of the adult. The remaining ten segments constitute the ab- domen. On the lower side of the abdomen there are five pairs of fleshy appendages, which are known as the prolegs ; these are borne by the third to the sixth and the last abdominal seer- ments. Each proleg is armed at the tip with a series of hooks by which it clings to the object upon which the caterpillar is walking, When a caterpillar changes to a chrysalis the prolegs are lost, being shed with the last larval skin.

The larvae of butterflies differ greatly in re- spect to the clothing of the body ; some are ap- parently naked, the few hairs with which the body is clothed being inconspicuous (see Plate XI, Fig. 2) ; with others the hairs are more numerous and larger (Plate IV, Fig. 1) ; and still others are clothed with large spines (Plate XXV, Fig. 2).

22

GENERAL ACCOUNT OF BUTTERFLIES

All insects in the course of their development shed their skin at regular intervals. This process is termed molting, and the cast skin is referred to as the exuvice (ex-u'vi-ae).

Before an insect molts a new skin is formed beneath the old one ; then the old skin bursts open, and the insect crawls forth, clothed in a soft skin, which stretches, if necessary, to accommo- date the increased size of the insect. Very soon, however, this new skin becomes hard. Caterpil- lars molt four or five times during their larval life ; some other insects molt many more times.

When a caterpillar is full-grown it makes preparation for the quiet period that is to follow. The larvae of some moths go into the ground and form a cell within which the pupa state is passed; the larva; of others spin a dense silken case about the body which is known as the cocoon ; some of these cocoons are familiar objects. The larvae of skippers, which are commonly classed with but- terflies (see Part III), spin a cocoon ; but almost no true butterflies do so.

A few butterflies undergo their transforma- tions in a crevice or cell upon or in the ground ; but nearly all species fasten themselves to some object and hang suspended during the pupa stage.

There are two distinct methods of suspension;

HOW TO KNOW THE BUTTERFLIES

in one, the chrysalis hangs suspended by the tail alone (Plate I, Fig. 3), in the other, the tail is fastened in a similar manner, but there is also a girth about the middle of the body (Plate III,

Fig- 3)-

When a caterpillar is full-grown it stops eat- ing and seeks a convenient place in which to transform. It then spins, upon the object to which it is to fasten itself, a button of silk, into which it fastens the prolegs at the hind end of the body. Plate II, Figure 1, represents a cater- pillar which has done this and is ready to trans- form ; and Plate III, Figure 2, represents another caterpillar which has suspended itself by a button at the tail and a girth about the middle of the body.

After suspending itself, the caterpillar rests for a time ; then its skin splits open in the middle of the back, and the head end of the body is worked out through this opening. Plate II, Figure 2, represents one which was photographed just as it reached this stage in the transformation. As the shed skin dries it shrinks back toward the tail, where it is attached to the button of silk. Before the body is entirely freed from the skin, the tail of the chrysalis, which is armed with hooks, is withdrawn from it and firmly fast- ened to the button of silk.

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PLATE III

THE FIRST THREE STAGES OF A BUTTERFLY Fig.

i. Eggs of the Cabbage-butterfly; greatly enlarged.

2. Full-grown larva of the Cabbage-butterfly, fastened up by a button

of silk at the tail and a girth around the middle, ready to trans- form ; enlarged.

3. Chrysalis of the Cabbage-butterfly ; enlarged.

(From photographs by Professor M. V. Slingerland, colored by Mrs. Slingerland.)

GENERAL ACCOUNT OF BUTTERFLIES

The duration of the chrysalis state varies greatly ; in the summer time in many cases it is only a few days ; on the other hand, it may be several months, as is the case with those that pass the winter in this state.

When the butterfly emerges from the chrysa- lis skin, the wings are at first small and limp. The butterfly hangs for a time by the legs ; the wings expand rapidly, and soon become stiff and fitted for flight. On Plate 1, Figure 4, and Plate XXV, Figure 3, are represented recently emerged butterflies which were waiting for their wings to dry.

V. THE STUDY OF THE LIFE OF BUTTERFLIES

If one would know the butterflies he must study their lives, and their relations to each other. We do not feel that we are acquainted with a man when we merely know his name ; and our acquaintance with a butterfly is only begun when we have determined its species. The learning of the names of species should be regarded as merely a means, not the end of our studies. It is neces- sary to learn by what name an insect is known in order to find out what has been published regard- ing' it ; but having- learned the name we should not stop there. The name is merely the kev that

25

HOW TO KNOW THE BUTTERFLIES

will let us into the storehouses of knowledge ac- cumulated by our predecessors.

The determining of the name of a butterfly may teach us much about the insect if it be done in the better way ; for there are two ways in which the names of the species described here can be determined. The student may learn the name by comparing a specimen with the pictures. This is probably the way in which many who use the book will begin ; and some will not be able to devote the time to this subject necessary to study it in a more serious manner.

But there is another way of classifying our specimens, one by means of which we may learn something of the relation of the various kinds to each other, and of their distinguishing: character- istics, that is, by the use of the analytical tables, which are given throughout the book. The stu- dent is advised, even when he knows the name of a species, to make use of the tables for the sake of learning the distinctive characteristics pointed out in them.

After a species has been properly classified, we are ready to begin the study of its life. This will be found to be the most fascinating part of the study ; for it includes the watching of the ways of the butterflies in the field, the observing

26

GENERAL ACCOUNT OF BUTTERFLIES

of their transformations, and, often, the working out of the relations between the different forms of the same species.

In studying the transformation sone may be- gin either with larvas or with eggs ; the latter way is the more desirable, but more difficult. By careful watching, one can often see a butterfly laying its eggs upon the food plant of its larva, and in this way obtain them ; but if one fails to find the eggs, it is easy to find the larvae later. In many cases the eggs can be readily obtained by caging a living female butterfly with the proper food plant.

Breeding-cages are nec- essary for rearing cater- pillars. A good home- made cage can be built by fitting a pane of glass into one side of an empty soap- box. A board, three or four inches wide, should be fastened below the glass so as to admit of a layer of soil being placed in the lower part of the cage, and the glass can be made to slide, so as to serve as a door (Fig. 13). The glass should fit closely when shut, to prevent the escape of

*7

Fig. 13. A home-made breeding-cage.

HOW TO KNOW THE BUTTERFLIES

insects. The soil is put into the box so that if larvae of moths are reared they may have a chance to go into the ground to transform.1

Branches of the proper food plant should be stuck into bottles or cans which are filled with sand saturated with water. By keeping the sand wet the plants can be kept fresh longer than in water alone, and the danger of the larvae being drowned is avoided by the use of sand.

Hibernating chrysalids may be left in the breeding-cages or removed and packed in moss in small boxes. Great care should be taken to keep moist the soil in the breeding-cages, or the moss if that be used. The cages or boxes con- taining the pupa; should be stored in a cool cellar, or in an unheated room, or in a box placed out of doors where the sun can not strike it. Low temperature is not so much to be feared as great and frequent changes of temperature.

An excellent breeding-cage can be made by combining a flower-pot and a lantern-globe or a large lamp-chimney ; the top of the lantern-globe is covered with Swiss muslin.

The student of butterflies needs a collect-

'The following suggestions for breeding insects and the care of speci- mens are taken, in large part, from the work by the senior author, Insect