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BUTTERFLIES

PART I
INTRODUCTION

     In popular esteem the butterflies among the insects are what the birds are among the higher animals--the most attractive and beautiful members of the great group to which they belong. They are primarily day fliers and are remarkable for the delicacy and beauty of their membranous wings, covered with myriads of tiny scales that overlap one another like the shingles on a house and show an infinite variety of hue through the coloring of the scales and arrangement upon the translucent membrane running between the wing veins. It is this characteristic structure of the wings that gives to the great order of butterflies and moths its name Lepidoptera, meaning scale-winged

     In the general structure of the body, the butterflies resemble other insects. There are three chief divisions: and abdomen. The head bears the principal Sense Organs; the thorax, the organs of locomotion; and the abdomen, the organs of reproduction.

     By examining a butterfly's head through a lens it is easy to see the principal appendages which it bears. Projecting forward from the middle of the top is a pair of long feelers or antennae. Each of these consists of short joints which in general may be divided into three groups: first, a few large joints at the base connecting the feeler with the head; second, many rather small joints which make up the principal length; third, several larger joints which make up the outer part or "club" of the antenna. In the case of the Skippers, there are in addition a number of small joints coming to a sharp point at the end of the club. Just below the insertion of the antennae on each side of the head are the large compound eyes, which are almost hemispherical. With a powerful glass, one can see the honeycomb-like facets, of which there are thousands, making up each eye. Just below the eyes there are two hairy projections, called the palpi, between which is the coiled tongue or sucking tube. (See plate)


Butterfly Antennae, magnified. (From Holland)

     Anatomically the thorax is divided into three parts-the prothorax, the mesathorax, and the metathorax; but the lines of division between these parts are not easily seen without denuding the skin of its hairy covering. The prothorax bears the first pair of legs. The mesathorax bears the front pair of wings and the second pair of legs. The metathorax bears the hind pair of wings and the third pair of legs. In many butterflies, the first pair of legs are so reduced in size that they are not used in walking.

     The abdomen is composed of eight or nine distinct rings or segments, most of which have two spiracles or breathing pores, one on each side. It also bears upon the end of the body the ovipositor of the female or the clasping organs of the male.

BUTTERFLY TRANSFORMATIONS

     The butterflies furnish the best known examples of insect transformations. The change from the egg to the caterpillar or larva, from the caterpillar to the pupa or chrysalis, and from the chrysalis to the butterfly or imago is doubtless the most generally known fact concerning the life histories of insects. It is a typical example of what are called complete transformations as distinguished from the manner of growth of grasshoppers, crickets, and many other insects in which the young that hatches from the egg bears a general resemblance to the adult and in which there is no quiet chrysalis stage when the little creature is unable to eat or to move about.


Egg of Baltimore Butterfly, much magnified. (From Holland)

The Growth of the Caterpillars

     Caterpillars are like snakes in at least one respect: in order to provide for their increase in size they shed their skins. When a caterpillar hatches from the egg it is a tiny creature with a soft skin over most of its body but with rather a firm covering for its head. While we might fancy that there could be a considerable increase in size provided for by the stretching of the soft skin it is easy to see that the hard covering of the head will not admit of this. So the story of the growth of a caterpillar may be told in this way:

     A butterfly lays an egg upon a leaf. Some days later the egg hatches into a larva, which is the technical name for the second stage of an insect's life. In the case of the butterfly we call this larva a caterpillar. The little caterpillar is likely to take its first meal by eating the empty egg shell. This is a curious habit, and a really satisfactory explanation of it seems not to have been made. Its next meal is likely to be taken from the green tissues of the leaf, commonly the green outer surface only being eaten at this time. The future meals are also taken from the leaf, more and more being eaten as the larva gets older.

     After a few days of this feeding upon the leaf tissues the little caterpillar becomes so crowded within the skin with which it was born that it is necessary to have a larger one. So a new skin begins to form beneath the first one. Consequently the latter splits open in a straight line part way down the middle of the back just behind the head. Then the new head covering is withdrawn from the old one and the caterpillar wriggles its way out of the split skin and finds itself clothed in a new one. At first all of the tissues of the new skin are soft and pliable and they easily take on a larger size as the body of the caterpillar expands. A little later these tissues become hardened and no further expansion is possible.

    This process of skin-shedding is called moulting. The cast skin is often called the exuviac. The period of the caterpillar's life between the hatching from the egg and this moult is often called a stage or instar--that is, the caterpillar up to the time of this moult is living in the first caterpillar stage or instar.

     During the actual moulting the caterpillar is quite active in freeing itself from the exuviae. But as soon as it is free it is likely to rest quietly for some hours while the tissues of the new skin are hardening. Then it begins feeding upon the leaf again and continues taking its meals at more or less regular intervals for several days. By that time it will again have reached its limit of growth within this second skin and the process of moulting must be repeated. It takes place in the same way as before and the caterpillar enters upon the third instar of its larval life.

     This process of feeding and moulting is continued for several weeks, the number of moults being usually four. During the later stages the increase in size is more marked each time the skin is shed, until the caterpillar finally reaches its full growth as a larva and is ready for the wonderful change to the quiet chrysalis in which all its caterpillar organs are to be transformed into the very different organs of the butterfly.

     In the case of butterfly larvae one of the most interesting features of the growth of the caterpillar is that of the remarkable changes in colors and patterns of marking which the caterpillar undergoes. One who had not followed these changes would often be at a loss to recognize caterpillars of slightly differing sizes as belonging to the same species. These changes commonly show a remarkable adaptation to the conditions of life, and generally tend to the concealment of the caterpillar upon its food plant. The stages of growth of the green-clouded swallowtail caterpillar are illustrated on plate opposite page 80.

    Before each moult the caterpillar is likely to spin a silken web upon the leaf surface. It then entangles its claws in the web to hold itself in place while the skin is cast. (See plate.)

The Change to the Chrysalis

     A week or ten days after the last moult of its caterpillar growth the larva commonly becomes full fed and ready to change to the chrysalis state. The details of the way in which this is accomplished vary greatly with different butterflies, as will be noted in the stories of many species later in this book. In general, however, the caterpillar provides a web of silk which it spins against some surface where the chrysalis will be secure and in this web it entangles its hind legs. Sometimes there is the additional protection of a loop of silk over the front end of the body. After the legs have become entangled downward until the skin splits open along the median line of the back and gradually shrinks upward until it is almost free, showing as it comes off a curious creature which has some of the characteristic features of a chrysalis. It is seldom at this stage of the same shape as the chrysalis. When the caterpillar's skin is nearly off this chrysalis-like object usually wriggles its body quickly in a manner to entangle a curious set of hooks attached to the upper end in the web of silken thread. This hook-like projection is called the cremaster, and it serves a very important purpose in holding the chrysalis in position.

     As soon as the cremaster is entangled in the web the cast skin usually falls off and for a very short period the creature hanging seems to be neither caterpillar nor chrysalis. It is in fact in a transition stage between the two, and it very soon shortens up and takes on the definite form of the chrysalis, the outer tissues hardening into the characteristic chrysalis skin.

     From the fact that this chrysalis skin shows many of the characteristic features of the future butterfly it is evident that the change from the caterpillar to the butterfly really began during the life of the larva. The nature of the process by which this change takes place has long been a puzzle to scientists. For the making of a butterfly is one of the most wonderful phenomena in the outer world, and it has challenged the attention of many acute observers. Some two centuries ago the great Dutch naturalist, Swammerdam, studied very carefully the development of many insects, especially the butterfly. He found that if he placed in boiling water a caterpillar that was ready to pupate or become a chrysalis, the outer skin could easily be removed, revealing beneath the immature butterfly with well-developed legs and antennae. From these observations he was led to believe that the process of growth was simply a process of unfolding; that is, as Professor Packard has expressed it, "That the form of the larva, pupa, and imago pre-existed in the egg and even in the ovary; and that the insects in these stages were distinct animals, contained one inside the other, like a nest of boxes or a series of envelopes one within the other." This was called the incasement theory and it was held to be correct by naturalists for nearly a century. It was discredited, however, about a hundred years ago, but not until another fifty years had passed was it definitely replaced by another and much more convincing theory propounded by Weismann.

     According to Weismann's theory, which is now well-established, the process of development internally is a much more continuous one than the external changes would indicate. So far as the latter are concerned we simply say that a caterpillar changes to a chrysalis and a chrysalis to a butterfly, the transition in each case requiring but a very short time. Internally, however, it has been going on almost continuously from the early life of the caterpillar. The various organs of the butterfly arise from certain germinal disks or "imaginal" buds, the word "imaginal" in this case being an adjective form of imago, so that the imaginal buds are really simply buds for the starting of growth of the various organs of the imago or adult. As the caterpillars approach the chrysalis period these imaginal buds rapidly develop into the various organs of the butterfly. This process is helped along by the breaking down of many of the tissues of the larva, this broken-down tissue being then utilized for the production of the new organs. About the time the chrysalis is formed this breaking-down process becomes very general, so that the newly formed chrysalis seems largely a mass of creamy material which is soon used to build up the various parts of the butterfly through the growth of the imaginal buds.

The Change to the Butterfly


     There is probably no phenomenon in the world of living creatures which has attracted more attention than the change of the chrysalis into the butterfly. It is not strange that this is so. We see upon a tree or shrub or wall an inert, apparently lifeless object, having no definite form which we can compare it with other things, having eyes nor ears nor wings nor legs--an object apparently of as little interest as a lifeless piece of rock. A few minutes later we behold it again and note with astonishment that this apparently inanimate being has been suddenly transformed into the most ethereal of the creator earth, with an exquisite beauty that cannot fail to attract admiration, with wings of most delicate structure for flying through the air, with eyes of a thousand facets, with organs of smell that baffle the ingenuity of man to explain, with vibrant antennae, and a slender tongue adapted to feeding upon the nectar of flowers--the most ambrosial of natural food. So it is not strange that this emergence of a butterfly has long been the theme both of poets and theologians and that it attracts the admiring attention of childhood, youth, and age.

     Fortunately, this change from chrysalis to butterfly may readily be observed by any one who will take a little to rear the caterpillars or to watch chrysalids found outdoors. The precise method of eclusion, as we this new kind of "hatching," varies somewhat with different species but in general the process is similar in all.

     Those chrysalids which have a light colored outer skin are especially desirable if we would watch this process. One can see through the semi-transparent membrane the butterfly within, until finally, just before it is to break out, the markings of the wings and body Show distinctly. If at this time the chrysalis is placed in to come out at once, so that you can observe it readily. It usually breaks apart over the head and the newly released legs quickly grasp hold of the empty skin as well as of the support to which it is attached. It then hangs downward with a very large abdomen and with the wings more or less crumpled up, but decidedly larger than when they were confined within the chrysalis. The wings, however, soon begin to lengthen as they are stretched out, probably through the filling of the space by the body juices. Commonly, the hind pair of wings become full size before the front ones. In a short time the wings attain their full size, the abdomen becomes smaller, through the discharge of a liquid called meconium, and the butterfly is likely to walk a few steps to a better position where it will rest quietly for an hour or two while body and wing tissues harden. After this it is likely to fly away to lead the free life of a butterfly. (See plate.)

    These changes from larva to chrysalis and from chrysalis to adult in the ease of the Monarch Butterfly are illustrated on the plates opposite pages 32-33. A little study of these photographs from life will help greatly to an understanding of the process.

     Some very interesting observations have been made by Mr. J. Alston Moffat upon the method of the expansion of the wings. In summarizing his investigations he writes:

     "When a wing is fully expanded, and for an hour or two after, the membranes can be easily separated. Entrance for a pin-point between them is to be found at the base of the wing where the subcostal and median nervures come close together. The membranes are united at the costal and inner edges, which have to be cut to get them apart; but they are free at the outer angle. At that time the nervures are in two parts, half in one membrane and half in the other, and open in the centre. The fluid which has been stored up in the pupa enters the winglet at the opening referred to, expanding the membranes as it passes along between them, and the nervures at the same time, and when it has extended to every portion of the wing, then it is fully expanded. The expanding fluid is of a gummy consistency, and as it dries, cements the membranes together, also the edges of the half-nervures, and produces the hollow tubes with which we are so familiar."

BUTTERFLIES AND MOTHS

     The butterflies and moths both belong to the great order of scale-winged insects--the Lepidoptera. They are distinguished, however, by certain general characteristics, which hold true for the most part in both groups. The butterflies fly by day; the moths fly by night. All of the higher butterflies go into the chrysalis state without making a silken cocoon, while most of the higher moths make such a cocoon. The bodies of the butterflies are usually slender, while those of the larger moths are stout. The antennae of the butterflies are generally slender and commonly enlarged at the tip into a miniature club. The antennae of the larger moths are commonly feathery or are long and slender, tapering gradually toward the tip.


Butterfly wing scales, magnified. (From Holland)

     The characteristic features that distinguish a moth from a butterfly are well illustrated in the plate opposite page 49, which shows one of the largest and most beautiful moths in the world. It is the Cynthia moth. As may be seen, the newly emerged moth is resting upon the silken cocoon in which it spent its period as a pupa or chrysalis. This cocoon was attached by the caterpillar to the twig from which it hangs at the time it spun the cocoon. The feathered antennae, the hairy legs, the thick thorax, and large abdomen--all show very clearly in this side view of the moth. As will be seen, the wings are large and very suggestive of those of a butterfly and have the characteristic eye-spots toward the tip and the crescent marks in the middle, which are so often found on the wings of the larger moths.

     Some of these large moths on cloudy days occasionally fly during daylight and, by the uninitiated, they are often mistaken for large butterflies. One who will notice their structure, however, will readily see the characteristic features of the moth.

     In the caterpillar stage, there are no hard and fast differences between the larvae of butterflies and those of the higher moths. In each ease, the insect consists of a worm-like body, having a small head provided with biting jaws and simple eyes or ocelli. Back of the head are the three rings of the thorax, each of which bears a pair of jointed legs. Back of these three rings there are a considerable number of other body rings making up the abdomen, on the middle of which there are commonly four or five pairs of fleshy prolegs, not jointed but finished at the tip with fine claws. At the hind end of the body there is another pair of prolegs similar in structure.

THE SCENTS OF BUTTERFLIES

     Many students of American butterflies have occasionally mentioned the fact that certain species seem to give off a scent which has frequently been spoken of as a fragrance, suggesting sandalwood or some other odor. The general subject as exemplified by of other lands has been studied for many years Fritz Muller; and certain English entomologists have attention to it. A translation of the publications and an excellent summary of our pre-knowledge of the subject is published in Dr. Longstaff's on butterfly hunting.

     The odors given off by butterflies are divided into two principle kinds, namely: first, those which are repulsive to senses of man, and evidently for the purpose of protecting the butterflies from birds and other vertebrate are found in both sexes; second, those which are evidently for the Purpose of sexual attraction and confined to the male butterflies--these scents are usually attractive to the senses of man.


Androconia from wings of male butterflies

     The aromatic scents of the second group are generally produced by means of certain scales or hairs of many curious forms, which are scattered over the surface of the wings or are placed within certain pockets, generally near the borders of the wings. These scales or hairs are called androconia. Some of them much magnified are represented in the picture above.

       Our knowledge of the scents given off by American butterflies is very fragmentary, and it is highly desirable that many more observations should be made upon the subject. If collectors generally would make careful notes, both in the field and upon the freshly killed butterflies at home, we ought soon to be able greatly to extend our knowledge. By holding the butterfly with a pair of forceps, one can often determine whether the fragrance is emitted. It is often helpful also to brush the hairs or tufts where the androconia are attached, using a small, dry camel's hair brush for the purpose.

BUTTERFLY MIGRATIONS

Migration seems to be a general instinct in the animal. world, developed when a species becomes enormously abundant. At such times this instinct apparently overcomes all others and the creatures move on regardless of obstacles and conditions that may mean certain death to the vast majority. Such migrations among mammals have often been recorded, one of the most notable examples being that of the little lemmings which migrate at periodical intervals in a way which has often been described. Among the insects such migrations have been frequently noticed, and the phenomenon has apparently been observed oftener among the butterflies than in any other group. Entomological literature during the last hundred years contains a great many records of enormous flights of butterflies over long distances, extending even from Africa into Europe or from one part of America to another far remote. As such migration is likely to happen whenever a species becomes extremely abundant it probably is Nature's way of providing for an extended food for the succeeding generations. That it results in the death of a majority of the migrants is doubtless true, but it must lead to vast experiments in extending the geographical area inhabited by these species. Numerous examples of such migrating swarms will be found in the pages of this little book. (See plates.)


Photographed from life by A. H. Verrill.
SWALLOWTAIL BUTTERFLY JUST OUT OF ITS CHRYSALIS.
THE CHRYSALIS SKIN BELOW.

Photographed from life.
THE HAMMOCK CATERPILLAR ON ITS HAMMOCK.

TIGER SWALLOWTAIL

     The migrations thus considered are only exceptional occurrences. There is, however, a regularly recurring annual migration on the part of some butterflies which is also a phenomenon of extraordinary interest. The most notable example is that of the Monarch which apparently follows the birds southward every autumn and comes northward again in spring. There is much evidence to indicate that in some slight degree other butterflies have a similar habit, although the present observations are inadequate to determine to what extent this habit has be come fixed in most of these species.

HIBERNATION OR WINTER LETHARGY

     The ways in which butterflies spend the winter are always of peculiar interest to the naturalist. Here are creatures with four distinct stages of existence, each of the possibility of carrying the species through of cold. It is necessary to learn for each insect which stage has been chosen for the purpose, and if find the reasons for the choice.

     As a rule, the related members of a group are likely to hibernate in a similar stage. Thus most of the Swallowtails pass the winter as chrysalids while practically all the pass Angle-wings pass the winter as adults. This rule, however, has many exceptions, for one will often find closely related species which differ in the stage of hibernation.

     As one would expect, the conditions of hibernation vary greatly with the latitude. In the severe climate of the far north the conditions are likely to be more uniform than in the South Where the milder climate permits greater variation to the insect. In some cases where a butterfly hibernates in only one stage in Canada it may pass the winter in two or more stages in Alabama or Florida.

     In many other orders of insects the egg is a favorite stage for hibernation. Even in the closely related moths it is often chosen by many species, but comparatively few butterflies pass the winter in the egg stage. The little Bronze Copper may serve as one example of this limited group.

     The conditions as to hibernation by the larvae of butterflies are very different from those of the egg. It has been estimated that probably half of all our species pass the winter in some stage of caterpillar growth. This varies all the way from the newly hatched caterpillar which hibernates without tasting food to the fully grown caterpillar which hibernates full fed and changes to a chrysalis in spring without eating anything at that time. A large proportion, however, feed both in fall and spring, going through the winter when approximately haft grown.

     The Graylings and the Fritillaries are typical examples of butterflies which hibernate as newly hatched larvae. The eggs are laid in autumn upon or near the food plants and the caterpillars gnaw their way out of the shells and seek seclusion at once, finding such shelter as they may in the materials on the soil surface. In spring they begin to feed as soon as the weather permits and complete their growth from then on.

     The half-grown caterpillars may hibernate either as free creatures under boards, stones, or in the tuffy grass, or they may be protected by special shelters which they have provided for themselves in their earlier life. In the case of the latter each may have a shelter of its own or there may be a common shelter for a colony of caterpillars. Among the examples of those hibernating in miscellaneous situations without special protection the caterpillars of the Tawny Emperor, the Gray Emperor, the Pearl Crescent, and some of the Graylings are examples. Among those which hibernate in individual shelters the Sovereigns, among which our common Viceroy is most familiar, are good examples. Among those which hibernate in a tent woven by the whole colony for the whole colony the Baltimore or Phaeton butterfly is perhaps the best example.

     The caterpillars that hibernate when full grown may be grouped in a way somewhat similar to those which are half grown. Many species simply find such shelter as they may at or near the soil surface. The Clouded Sulphur is a example of these. Others pass the winter in individual shelters made from a leaf or blade. Several of the larger Skippers are good examples of this condition. So far as I know none of our species pass the winter in colonial shelters when full grown.

     It would be natural to suppose that the great majority of butterflies would be likely to hibernate in the chrysalis state. Here is a quiet stage in which the insect is unable to move about or to take any food, in which it seems entirely dormant and as a rule is fairly well hidden from the view of enemies. We find, however, that only a rather small proportion of our butterflies has chosen this stage for survival through the winter. The most conspicuous examples are the Swallowtails, nearly all of which hibernate in the chrysalis stage. Other examples are the various Whites, the Orange-tips, and isolated species like the Wanderer, and the Spring Azure and the American Copper. Practically all the butterflies that pass the winter as chrysalids have a silken loop running around near the middle of the body which helps to hold them securely through the long winter months. Apparently none of those chrysalids which hang straight downward are able to survive the winter.

     An adult butterfly seems a fragile creature to endure the long cold months of arctic regions. Yet many of our most beautiful species habitually hibernate as adults, finding shelter in such situations as hollow trees, the crevices in rocks, the openings beneath loose bark or even the outer bark on the under side of a large branch. It is significant that most of the adult-wintering Angle-wings are northern rather than Southern species, some of them being found in arctic regions practically around the world. One of the few southern forms that hibernates as an adult is the Goatweed Emperor.

    These examples are all cases of true hibernation in a lethargic condition. There are certain butterflies, however, which pass the winter as adults that remain active during this period. Obviously this is impossible in latitudes where the winter is severe, and it involves migration to a warmer climate. The one notable illustration of this is the Monarch butterfly which apparently flies southward to the Gulf states at least and there remains until spring, when individuals come north again. The Southward migration may be begun in Canada when the butterflies gather together in enormous flocks that remind one of the of the gathering of the clans with the migrating birds. This is one of the least understood of insect activities but it has been observed so often and over so long a period of years that there seems to be no questioning the general habit.

     Like everything else in relation to living things there are numerous variations in the prevailing modes of hibernation. In the case of many species one can find combinations of two or more stages in which the winter is passed. probably if we could observe with sufficient care we might be able to find somewhere examples of almost any conceivable double combination--as egg with larva or chrysalis or adult--the insect hibernating in two of these stages. examples are known in which both chrysalis and adult of the same species pass the winter and also of those in which young and well-grown larvae pass the winter. As one would expect, the conditions as to such combinations are to be more variable in southern than in northern regions.

     Notwithstanding all the attention which has been paid to butterfly life-histories there is still some uncertainty in regard to the hibernation of many of our species. One of the most interesting series of observations which a young naturalist could undertake would be to learn positively how which species of butterfly in his locality passes the winter.

AESTIVATION OR SUMMER LETHARGY

     In some species of butterflies there is a special adaptation to passing through the hottest part of the summer season in a state of lethargy which is suggestive of the torpor of the hibernating period. This phase of butterfly existence has not been extensively studied and there are indications that it exists more generally than has been commonly supposed. It has been noticed even in northern New England that some of the Angle-wings seek shelter and become lethargic during August. Apparently this is an adaptation to single broodedness, helping to carry the species through the year without the exhaustion incident to the continued activity of the butterfly.

     In more southern regions, especially in the hot, dry climates where vegetation withers in midsummer, it is well known that some caterpillars become lethargic, remaining inactive until the fall rains start vegetation into growth. The Orange-sulphur butterfly is a good example of this.

    This summer lethargy offers excellent opportunity for careful study. Any observer who finds a butterfly hidden away in summer under boards, the bark of a tree, or in a stone pile should look carefully to see what species it is and how the butterfly behaves. Such observations should be sent to the entomological journals in order that our knowledge of the subject may be increased.

FEIGNING DEATH

     The fact has long been noticed that various butterflies have the habit at times of feigning death and dropping to the ground where they may lie motionless for a considerable period. This habit is most easily observed in some of the Angle-wings, especially those which hibernate as adults. Those species have the under surfaces of their wings colored in various bark-picturing patterns and apparently live through the winter to some extent, resting beneath the bark of large branches or upon the trunks of trees. Many of them also secrete themselves in hollow trees or beneath loose bark or in board piles or stone walls. It is probable, however, that during the long ages when insects were adapting themselves to their life conditions, before man interfered with the natural order and furnished various more or less artificial places for hibernation, these butterflies rested more generally upon the under side of branches than they do now.

     Even in warm weather when one of these butterflies is disturbed it is likely to fold its legs upon its body drop to the ground, allowing itself to be handled without showing any signs of life. This habit is doubtless of value, especially during hibernation or possibly during the summer lethargy or aestivation, the latter a habit which be more general among these butterflies than is now supposed. As the insect lies motionless upon the ground it is very likely to blend so thoroughly with its surroundings that it becomes concealed, and any bird which had startled it from the branch above would have difficulty in finding it.

     Some very interesting observations have been made the death-feigning instincts of various other insects, specially the beetles. But no one so far as I know has yet made an extended study of the subject in relation to our butterflies. It is an excellent field for investigation and offers unusual opportunities for photographic records. One of the pictures opposite page 32 shows a photograph which I took of a Mourning Cloak as it was thus playing 'possum. This species exhibits the instinct to a marked degree.

COLORATION

     The caterpillars of butterflies and moths form a large part of the food of insect-eating birds. These caterpillars are especially adapted for such a purpose and in the economy of nature they play a very important part in keeping alive the feathered tribes. During the long ages through which both birds and insects have been developing side by side, there have been many remarkable inter-relations established which tend on the one hand to prevent the birds from exterminating the insects and on the other to prevent the insects from causing the birds to starve. The most important of these, so far as the caterpillars are concerned, are the various devices by which these insects protect themselves from attack, by hiding away where birds are not likely to find them, by clothing their bodies with spiny hairs, by other methods of rendering themselves distasteful, or by various phases of concealing coloration. On the whole, the examples of the latter are not so numerous or so easily found in the case of the larvae of butterflies as in those of moths.

     Perhaps the basal principle of concealing coloration is the law of counter-shading, first partially announced by Prof. E. B. Poulton, and later much more elaborately worked out by Mr. Abbott H. Thayer, and discussed at length by Mr. Gerald H. Thayer in his remarkable volume, "Concealing Coloration in the Animal Kingdom." The law of counter-shading is tersely stated in these words: "Animals are painted by nature darkest on those parts which tend to be most lighted by the sky's light and vice versa." As this law works out on most animals that live on or near the ground, the upper part of the body exposed to the direct light from above is dark; and the under part, shut off from the upper light and receiving only the small reflection from below, is enough lighter to make the appearance of the creature in its natural environment of a uniform tone from back to breast.

     Nearly all caterpillars illustrate this law of counter-shading. If they are in the habit of feeding or resting with their feet downward the back will be darker and the under side lighter, but if they are in the habit of feeding or resting in the opposite position these color tones will be reversed. One can find examples of such conditions almost any summer's day by a little searching of trees or shrubs.

     This law of counter-shading, however, is really only the basis for the coloration of caterpillars or other animals. It tends, chiefly, to make the creature appear as a flat plane when seen from the side, and may be said in a way to prepare the canvas upon which Nature paints her more distinctive pictures. A great many examples of color markings that tend to conceal the caterpillar amid its natural surroundings may be found by any one who will study the subject and it offers one of the most interesting fields for investigating. The chapter on caterpillars in the above-mentioned book by Mr. Thayer should serve as a starting point for any one taking up the subject.

     Butterflies differ from caterpillars and from most other animals in the fact that their coloring is chiefly shown upon the flat surfaces of the wings. Consequently, there is less opportunity for the various phases of counter-shading which is so commonly shown in the larger caterpillars. The bodies of nearly all butterflies do exhibit this phenomenon, but these bodies are relatively so small that counter-shading plays but a little part in the general display.

     Upon the outstretched membranes of the butterflies' wings Nature through the long ages of development has painted a great variety of pictures. Those which tend to protect the insect by concealment amid its surroundings are most commonly spread on the under surface of the wings. Especially is this true in the case of those species which pass the winter as adults or which have the habit of resting upon the bark of trees, the sides of rocks, or the surface of the ground. We here find some of the most interesting examples of obliterative coloring that occur in nature. Some butterflies have taken on the look of tree bark, others the sombre appearance of weathered rocks, while still others are painted with the images of flowerets and their stems.

Dazzling and Eclipsing Colors

     Many of the butterflies, especially the Angle-wings, which are marked on the under surface in various protective colors, are admirable examples of that phase of animal coloring which is spoken of as dazzling coloration. This is apparently one of the most important protective devices to be found in Nature and the validity of it is now generally conceded by naturalists. One phase of it, which may be called eclipsing coloration, seems to have been first definitely formulated by the late Lord Walsingham, a famous English entomologist who enunciated it in an address as president of the Entomological Society of London. The most significant paragraphs in that address were these:

     "My attention was lately drawn to a passage in Herbert Spencer's 'Essay on the Morals of Trade.' He writes:

     "As when tasting different foods or wines the palate is disabled by something strongly flavored from appreciating the more delicate flavor of another thing afterward taken, so with the other organs of sense a temporary disability follows an excessive stimulation. This holds not only with the eyes in judging of colors, but also with the fingers in judging of texture.'

     "Here, I think, we have an explanation of the principle on which protection is undoubtedly afforded to certain insects by the possession of bright coloring on such parts of their wings or bodies as can be instantly covered and concealed at will. It is an undoubted fact, and one which have been observed by nearly all collectors of insects abroad, and perhaps also in our own country, that it is more easy to follow with the eye the rapid movements of a more conspicuous insect soberly and uniformly colored than those of an insect capable of changing in an instant the appearance it presents. The eye, having once fixed itself upon an object of a certain form and color, conveys to the mind a corresponding impression, and, if that impression is suddenly found to be unreliable, the instruction which the mind conveys to the eye becomes also unreliable, and the rapidity with which the impression and consequent instruction can be changed cannot always compete successfully with the rapid transformation effected by the insect in its effort to escape."

    Lord Walsingham then goes on to suggest that this intermittent play of bright colors probably has as confusing effect upon birds and other predaceous vertebrates as upon man; and that on this hypothesis such colors can be accounted for more satisfactorily than upon any other yet suggested. Since then the significance of this theory has been repeatedly pointed out by Professor Poulton, Mr. Abbott H. Thayer, and various other authorities upon animal coloring. The terms dazzling and eclipsing have been applied to the phenomenon.

     Shortly after Lord Walsingham propounded this theory I called attention(1) to its fitness in explaining some of the most interesting color phases shown by American insects, notably the moths and locusts which have brilliantly colored under wings and protectively colored upper wings.

     The animals of the north show numberless color phases of interest. One of the most curious of these is exhibited by several families of insects in which the outer wings are protectively colored in dull hues and the under wings brightly colored. For example, there are many species of moths belonging to the genus Catocala found throughout the United States. These are insects of good size, the larger ones measuring three inches in expanse of wings, and the majority of them being at least two thirds that size. Most of them live during the day on the bark of trees, with their front wings folded together over the back. The colors and markings of these wings, as well as of the rest of the exposed portions of the body, are such as to assimilate closely with the bark of the tree upon which the insect rests. In such a situation it requires a sharp eye to detect the presence of the moth, which, unless disturbed, flies only at night, remaining all day exposed to the attacks of many enemies. Probably the most important of these are the birds, especially species like the woodpeckers, which are constantly exploring all portions of the trunks of trees.

     The chief beauty of these Catocalas, as they are seen spread out in the museum cabinet, lies in the fact that the hind wings, which, when the moth is at rest in life, are concealed by the front ones, are brightly colored in contrasting hues of black, red, and white in various brilliant combinations. These colors, in connection with the soft and blended tones of the front wings, make a very handsome insect.

     It is easy to see that when one of these Underwing Moths is driven to flight by a woodpecker or other bark-searching bird it would show during its rapid, irregular flight the bright colors of the under wings which would be instantly hidden upon alighting and the very different coloring of the upper wings blending with the bark would be substituted. Consequently, the bird would be very likely to be baffled in its pursuit.

Coloration of Locusts:

     On the rocky hills and sandy plains of New England there are several species of grasshoppers or locusts that also illustrate these principles. If you walk along a strip of sandy land in summer, you start to flight certain locusts which soon alight, and when searched for will be found closely to assimilate in color the sand upon which they rest. On a neighboring granite-ribbed hill you will find few if any of this species of locust, but instead there occur two or three quite different species, which when at rest closely resemble the lichen-covered rocks. This resemblance is very striking, and is found in all stages of the insect's existence. If now you go to a lowland meadow, still another color phase will be found to prevail--the green grass is swarming with the so-called "long-horned" grasshoppers, which are green throughout with linear bodies, and long, slender legs and antennae.

     Each of these three groups of insects is adapted to its particular habitat. All are constantly persecuted by birds, and have been so persecuted for unnumbered ages in the past. In every generation the individuals have varied, some toward closer resemblance to environment, others in an opposite direction. The more conspicuous insects have been constantly taken, and the least conspicuous as constantly left to reproduce. Were the three groups to change places to-day, the green grasshoppers from the meadows going to sandy surfaces, the sandcolored locusts going to rocky hills, and the "mossbacks" from the hills to the lowland meadows, each would become conspicuous, and the birds would have such a feast as is seldom spread before them.

     The species living on sand and rocks are often "flushed" by birds. Those which flew but a few feet would be likely to be captured by the pursuing bird; those which flew foxther would stand a better chance of escaping. Similarly, those which flew slowly and in a straight line would be more likely to be caught than those which flew rapidly and took a zigzag course. As a consequence of the selection thus brought about through the elimination of those which flew slowly along the straight and narrow way that led to death, you will find that most locusts living in exposed situations when startled fly some distance in a rapid, zigzag manner.

     But still another element of safety has been introduced by some species of these locusts through the adoption of the color tactics of the Catocala moths. The under wings of the common Carolina locust--the species most abundant along the highway--are black, bordered with yellowish white. The base of the hind wings of a related species living on the Western plains is bluish, while in the large coral-winged locust of the Eastern states the hind wings are red, bordered with black. In nearly all of the species of these locusts frequenting open localities where they are liable to disturbance by birds or other animals, the hind wings exhibit contrasting colors in flight. Most of them also fly in a zigzag line, and alight in a most erratic manner. Many times I have had difficulty in determining the exact landfall of one of these peculiar creatures, and I believe Lord Walsingham's suggestion is well exemplified in them.

     The most famous example of a combination of this dazzling coloring of the upper wing surface with a definite protective coloring of the under wing surface is the Kallima butterfly which is illustrated in almost every book dealing with animal coloration. The under wing surface bears a striking resemblance to a leaf and the hind wings project to form a tail which looks like the petiole of the leaf, and there is also a mark running across the wings which mimics the midrib. When the butterfly is flying the brilliant colors of the upper surface are visible, but when it alights these are instantly replaced by the sombre tone of the under surface, so that apparently the insect completely disappears and in its place there is only a leaf attached to a branch in a most natural position. In Dr. Longstaff's book there is an illustration of another tropical butterfly, Eronia cleodora, which resembles on its under surface a yellow disease-stricken leaf but on its upper surface gives a brilliant combination of black and white. This insect alights upon the leaves which it resembles and is a striking example of both dazzling and mimicking coloration.

     Many of our own butterflies, notably the Angle-wings, are excellent examples of a similar combination. In flight they reveal conspicuous colors which are instantly hidden upon alighting and then one only sees the bark-like or dead leaf-like under surface as may be seen in the plate opposite pages 160-161. The iridescence upon the upper wing surface of many butterflies, whose under wing surface is colored in concealing tones, is doubtless also of great use to the insect in a similar way. There is a splendid opportunity here for some observer to study this phase of butterfly activity and to get photographs of the insects amid their natural surroundings.

     In their book upon "Concealing Coloration" the Messrs. Thayer have called attention to many interesting phases of dazzling coloration. They show that bright marks like the eye-spots or ocelli, which form so prominent a feature on the wing surfaces of many butterflies, really helped to conceal the insect amid its natural surroundings, by drawing the eye away from the outlines of wings and body so that the latter tend to disappear. Their discussion of this subject opens up another vast field for outdoor observations of absorbing interest, in which there is great need for many active workers.


BUTTERFLY FEIGNING DEATH, HANGING TO BARK BY ONE FOOT

BUTTERFLY IN HIBERNATING POSITION

THE MONARCH BUTTERFLY: CHANGE FROM CATERPILLER TO CHRYSALIS.
Photographs from life. [1 through 4]

1. CATERPILLAR FEEDING UPON LEAF OF MILKWEED

2. CATERPILLAR HUNG UP FOR THE CHANGE TO THE CHRYSALIS

3. THE TRANSITION STAGE

4. THE CHRYSALIS

THE MONARCH BUTTERFLY: THE CHANGE FROM CHRYSALIS TO ADULT.
Photographs from life.    [5 through 8]

5. CHRYSALIS SHOWING BUTTERFLY READY TO EMERGE

6. THE EMPTY CHRYSALIS

7. BUTTERFLY JUST OUT OF CHRYSALIS

8. SIDE VIEW A LITTLE LATER


THE CAROLINA LOCUST
Above, with wings expanded, as in flight


SELECTIVE COLOR SENSE

     One who collects the Underwing moths soon discovers that the light colored species which resemble the bark of birch trees are likely to be found upon the trunks of those trees, and that the dark colored kinds which resemble the bark of maple trees are likely to be found upon the trunks of these. Obviously, were this not true the protective coloring would avail but little and it is evident that these moths are able to select a background which is of advantage in helping to conceal them.

     There is much evidence to show that in a similar way the :butterflies are able by means of a well-developed color sense to select the places where they alight. One of the most notable examples is that of a South American species, Peridromia feronia. This is a silvery gray butterfly which alights head downward upon the bark of certain palm trees that have silvery gray stems and remains there with its wings fully expanded so that it utilizes the background in much the same way that the Underwing moths do. "When disturbed they will return to the same tree again and again."

     One who will observe the habits of our Angle-wings and other butterflies which have obliterative coloring of the under wing surface can easily learn that these insects select rather carefully the places where they alight. It will be found that as a rule each species utilizes a background that blends with its own coloring. It is probable that this habit is much more common in other groups of butterflies than has been realized. Much evidence of this sort has been collected regarding the butterflies of Europe and other countries, as well as near our own borders in America.

WARNING COLORATION AND MIMICRY

     The colors of a great many animals, including a considerable percentage of American butterflies and their larvae, have been commonly explained by the theory of warning colors. According to this theory animals which were for any reason not edible by birds and mammals have developed various striking combinations of color such as black and yellow, red and black, or black and white, in order to advertise to their foes their inedible qualities. This theory has been very generally accepted by naturalists and will be found expounded at length in many books published during the last quarter century.

     The whole subject of the validity of warning coloration has recently been brought up for reconsideration by the illuminating investigations of Mr. Abbott H. Thayer and discussed at length in the book upon "Concealing Coloration'' already mentioned. In an appendix to this book dated 1908 Mr. Thayer states that he no longer holds the belief that "there must somewhere be warning colors." He has convincingly shown that a large proportion of the animals which were supposed to be examples of this theory are really illustrations of concealing coloration. But there yet remain various facts which have been conclusively proven that apparently require the theory of warning colors to explain them. Here is another field in which there is a real need for much careful investigation under conditions that are rigidly scientific.

     Along with the theory of warning coloration the theory of mimicry has been propounded. According to this if a butterfly in a given region shows warning coloration, having developed such coloration because it is distasteful to birds and mammals, it may be mimicked by another butterfly in the same region belonging to another group, the latter butterfly being edible, but benefiting by its resemblance to the distasteful species, because birds or mammals mistake it for the latter and do not attempt to catch it. The most notable example of such mimicry in North America is that of the Monarch butterfly, which is supposed to be the distasteful species, and the Viceroy butterfly, which is supposed to mimic it. Several other instances of mimicry are found among our own butterflies, while in South America, Africa, and Asia there are numberless examples.

HELIOTROPISM

     It has long been known that the green surfaces of plants respond to the stimulus of the sun's rays in a most remarkable manner. This response has commonly been called heliotropism and it has been carefully studied by botanists all over the habitable world. More recently, the fact has been observed that many animals respond in certain definite ways to the stimulus of direct sunshine and the same term has been applied in this case. Very little attention has been given to the subject of heliotropism until within a few recent years. But the observations which have been made by Parker, Longstaff, Dixey, and others open up a most interesting field for further observation. An admirable summary of our present knowledge of the subject has been published by Dr. Longstaff in his book" Butterfly Hunting in Many Lands."

     One of the earliest observations upon this subject was that published in my book "Nature Biographies" which appeared in June, 1901, concerning the habit in the Mourning Cloak: "On a spring-like day early in November (the 8th) I came across one of these butterflies basking in the sunshine upon the ties of a railway track. It rested with its wings wide open. On being disturbed, it would fly a short distance and then alight, and I was interested to notice that after alighting it would always turn about until the hind end of its body pointed in the direction of the sun, so that the sun's rays struck its wings and body nearly at right angles. I repeatedly observed this habit of getting into the position in which the most benefit from the sunshine was received, and it is of interest as showing the extreme delicacy of perception toward the warmth of sunshine which these creatures possess."

     A little later, some very elaborate observations were made upon this habit of the Mourning Cloak by Prof. G. H. Parker of Harvard University. Professor Parker noticed that during the warm spells in winter the butterflies came out of their hiding places and after alighting, always placed themselves with their heads away from the direction of the sun and their bodies lying nearly at right angles to the sun's rays. By experiment, he found that they adjusted themselves to this position as soon as they were fully exposed to direct sunshine, even if at the time of alighting they were in a shadow. He found that this movement was a reflex action through the eyes, for when the eyes were blinded no such adjustment took place. He called it negative heliotropism.

     Dr. Longstaff uses the term orientation for this adjustment of the butterfly to the sun's rays and he finds it is a very general habit, especially with the Angle-wings, for the butterfly thus to orient itself after alighting, in such a way that the hind end of the body points toward the sun. This occurs not only with those species which keep their wings spread open when they alight but also with those in which the wings are closed together and held in a vertical position on alighting.

     Various explanations of this phenomenon have been offered but apparently none of them are yet generally accepted. Were the habit confined to butterflies like the Mourning Cloak, it would seem easy to prove that a main advantage was found in the benefit derived from the heat rays of the sun. Were it confined to those species which always fold their wings on alighting, it would seem easy to believe that it was a device for reducing the shadow east by the insect to its lowest terms. It has also been suggested that the habit is for the purpose of revealing to the fullest extent the markings of the butterfly. Evidently there is here an ample field for further investigation before definite conclusions are reached.

LIST AND SHADOW OBSERVATIONS

     Another field for most interesting studies upon the habits of living butterflies has been opened up by the very interesting discussion of list and shadow in Colonel G. B. Longstaff's fascinating book, "Butterfly Hunting in Many Lands." He there summarizes his numerous observations upon butterflies in various localities which he has seen to lean over at a decided angle when they alight. He defines "List" as "an attitude resulting from the rotation of the insect about its longitudinal axis, as heliotropism results from a rotation about an imaginary vertical axis at right angles to this." The name is adapted from the sailors' term applied to a vessel leaning to one side or another in a storm.

     Apparently this interesting habit was first called to the attention of European entomologists by an observation of Colonel C. T. Bingham made in 1878, but not published until long afterward. The observation was this:

     "The Melanitis was there among dead leaves, its wings folded and looking for all the world a dead, dry leaf itself. With regard to Melanitis, I have not seen it recorded anywhere that the species of this genus when disturbed fly a little way, drop suddenly into the undergrowth with closed wings, and invariably lie a little askew and slanting, which still more increases their likeness to a dead leaf casually fallen to the ground."

     Long before this was printed, however, a similar habit had been observed by Scudder in the case of our White Mountain butterfly (Oenis semidea). But this species is so exceptional in its habitat that the habit seems to have been considered a special adaptation to the wind-swept mountain top. The possibility of its being at all general among the butterflies in lowlands seems to have been overlooked.

     The observations recorded by Longstaff relate chiefly to various members of the Satyrid group. For example, a common Grayling, Satyrus semele, was watched many times as it settled on the ground. As a rule three motions are gone through in regular sequence: the wings are brought together over the back; the fore-wings are drawn between the hind wings; the whole is thrown over to right or left to the extent of thirty, forty, or even fifty degrees.

     This habit, of course, is of advantage to the insect. It seems possible that the advantage might be explained in either of two ways: first, the leaning over on the ground among grasses and fallen leaves might help to render the disguising coloration of the insect more effective, the large ocelli serving to draw the eye away from the outline of body and wing; second, the listing of the butterfly toward the sun tends to reduce the shadow and to hide it beneath the wings. There is no doubt that when a Grayling butterfly lights upon the ground in strong sunshine the shadow it casts is more conspicuous than the insect itself and the hiding of this might be of distinct advantage in helping it to escape observation. It is significant that in England the butterflies observed appear to lean over more frequently in sunshine than in shade. An observation of Mr. E. G. Waddilove, reported by Colonel Longstaff, is interesting in this connection:

     "A Grayling settled on a patch of bare black peat earth, shut up its wings vertically, and crawled at once some two yards to the edge of the patch to where some fir-needles, a cone or two, and a few brittle twigs were lying, and then becoming stationary threw itself over at an angle of some forty-five degrees square to the sun. It thus became quite indistinguishable from its surroundings."

     Apparently, some of the Angle-wings may have the same habit, for in Barrett's "Lepidoptera of the British Islands," there is a note in regard to Grapta C-album to the effect that it is fond of sunning itself in roads, on warm walls, or on the ground upon dead leaves in sheltered valleys. "Here, if the sun becomes over-clouded, it will sometimes close its wings and almost lie down, in such a manner that to distinguish its brown and green marbled under side from the dead leaves is almost impossible."

     Here is a most fascinating opportunity for American observers to determine definitely the facts in regard to our numerous species of butterflies that may show this habit. An observer with a reflex type of camera might easily be able to get pictures that would be of great value in helping to determine the principal facts in regard to the subject. Our common Graylings and numerous species of Angle-wings are so abundant and easily observed that they offer splendid opportunities to any one who will undertake a serious study of the subject.

PARASITIC ENEMIES

     All three of the earlier stages of butterflies egg, larva, and chrysalis--are subject to attack by various parasitic insects which develop at the expense of the host. Such parasites are probably the most important check upon the increase of butterflies, and along with birds, mammals, and bacterial diseases, they help to keep up that balance of nature which in the long run maintains a surprising uniformity in the numbers of each kind of butterfly.

     For the most part these insect parasites are small four-winged flies, although many of them are two-winged flies. In either case the life stages show a series of changes much like those of the butterflies themselves. Each parasite exists first as an egg, second as a larva, third as a pupa, and fourth as an adult fly. The larval stage, however, is simply that of a footless grub which lives within the body of its victim absorbing its life blood and gradually killing it.

     The parasites of butterfly eggs are legion. They are tiny flies whose life-story in briefest summary is this: The butterfly lays an egg. The parasite fly finds this egg soon after it is laid, and pierces the shell with her tiny, sharply pointed ovipositor and deposits inside of the shell her own microscopic egg. This egg within the egg soon hatches into a curious little larva that develops at the expense of the contents of the butterfly egg shell, and soon absorbs the whole of them. The parasite larva now changes to a pupa which a little later changes again to an adult fly like the one that laid the parasite egg in the beginning. Of course the butterfly egg never hatches into a caterpillar.

    One of the most interesting questions in regard to these egg parasites is this: How does the tiny parasitic fly find the newly laid egg? One would think that the proverbial search for a needle in a haymow would be an easy task compared with that of a fly about as large as the head of a pin finding a butterfly egg of singular size upon some part of one of the millions of leaves upon the trees and shrubs in field and forest. Yet the search is successful, as every one who has tried to get caterpillars from eggs found out of doors will testify. On a later page in this book, in connection with the story of the life of the Mourning Cloak butterfly, I have recorded some observations upon the little parasite which seemed to have been riding around upon the body of the butterfly waiting for her to lay her eggs.

     For one parasite upon the eggs of butterflies, there probably are dozens that attack the caterpillars. A large proportion of the butterfly larvae brought in from outdoors, especially those which are half-grown or more, will yield not butterflies but parasites. This is the experience of practically every one who attempts to rear these insects, and it emphasizes the value of the advice that in order to get fine specimens, it is desirable to rear them from eggs laid by butterflies beneath netting or in cages.

    The life-histories of the parasites that attack caterpillars vary greatly. The simplest are those of the large Ichneumon flies: The mother fly lays an egg beneath the skin of the caterpillar. The egg hatches into a larva that absorbs the fatty parts of the body of the caterpillar, gradually growing larger and larger until at last it reaches a length of possibly an inch. By this time it is likely to have absorbed so large a part of the inside of the caterpillar that the latter dies. The parasite larva now changes to a pupa, either inside or outside the skin of the caterpillar, and a little later changes again to an adult Ichneumon fly.

     In the case just given, one egg only was deposited within the skin of the caterpillar. In many others, however, a large number of eggs may be so deposited by a single fly. A special group of Ichneumon flies, called the Microgasters, contains many parasites that have this peculiarity. The Microgaster larvae on coming forth from the caterpillar have the habit of spinning tiny cocoons within which they change to pupae. By collecting some cabbage worms which are nearly full grown, and keeping them in a glass jar one can generally get a considerable number of these Microgaster cocoons and rear the flies from them.

     Another group of caterpillar parasites is still more minute. They are called the Chalcid flies. Their life-histories are full of interest, and might easily furnish opportunity for a long lifetime of study and experiment. One is likely to get hundreds of these Chalcid flies from a single caterpillar.


Tachinia Parasite: a, fly; b, puparium, magnified

     Another interesting group of parasites is that of the two-winged Tachina flies (see cut on this page). The life-story of some of these is comparatively simple: a buzzing fly, looking much like a large housefly, lays a small whitish egg upon the skin of a caterpillar. This egg is glued tightly and is large enough to be readily seen by the unaided eye. It hatches into a tiny larva that eats its way through the part of the shell glued to the caterpillar's skin, and through the latter at the same time. So the newly hatched Tachina larva finds itself in the body of its caterpillar host. It lives there, absorbing the fatty juices around it until at last it either kills or stupefies its unfortunate victim. It has then become full grown as a larva, and its last larval skin hardens into a brown pupa case within which the little creature changes into a pupa. It may or may not have burrowed through the skin of the caterpillar before this happened. A little later the pupa changes to a Tachina fly which breaks apart the pupa case and flies out into the world.

     It has lately been found, however, that many Tachinids have much more complicated life-histories than this. I have already discussed some of the more important of these in my book entitled, "Seeing Nature First".

    One can frequently rear parasites from the chrysalids of butterflies, but in many cases it is probable that these began their parasitic development in the caterpillars, which were able to change to chrysalids before being killed. In some cases, however, the chrysalids seem to be attacked, especially by certain Ichneumon flies.

REARING BUTTERFLIES FROM CATERPILLARS

     There are few things in the world more interesting to watch than the wonderful changes which a moth or butterfly goes through in the course of its life. You find on a tree or shrub a worm-like caterpillar. You take it in charge, placing it in a box or jar where you can provide leaves for its food and soon it either spins around itself a silken shroud, thus hiding from your sight, or else it simply seems to change to a lifeless object without eyes or wings or legs, unable to move about and motionless, save for a slight wriggle when you touch it. Yet if you keep the shroud or the mummy-like object for two or three weeks you are likely to see a beautiful moth come from the shroud or a glorious butterfly break out of the mummy case. (See plate.) So you can get the realest kind of moving pictures by simply bringing in the caterpillars that are easily found in garden, field, and wood.

     To collect these caterpillars it is only necessary to be provided with a pair of sharp eyes and an empty coffee can or some other form of tin box. Go out into the garden or along the borders of the woods. Look carefully. If you see places where leaves have been eaten, search the leaves near by and you are likely to find one or more of the caterpillars that caused the injury. Transfer them to the box and take them home with a few leaves of the food plant, There place them in some form of vivarium, which simply means a box or cage in which you can keep living creatures.

     The most satisfactory cages for rearing caterpillars are those which are open above so that there is not even a glass plate between the observer and the insect. This kind of vivarium is easily made by using a band of some sticky substance like the tree tangle-foot with which trees are commonly banded, or a strip of sticky fly paper. Any wide shallow box may be used by simply placing an inch-wide band of the sticky material around the vertical sides near the top. The caterpillars will be free to move all over the open box but they cannot cross the band to escape. Fresh leaves are easily placed in the open box and the withered ones removed.

     The same plan may be adopted with wide glass jars, like the ordinary battery jar. Choose a rather large one and smear the inner side near the top with a band of sticky material. The caterpillars are thus prevented from crawling out, but they are open to observation at all times. (See plate.)

     In the case of the caterpillars that change to butterflies no soil need be placed in the bottom of the jar as these will attach their chrysalids to the sides or to a stick or board which may easily be put in. In the case of many caterpillars that change to moths, however, it is desirable to place about two inches of soil in the bottom of the jar. Then if the caterpillars are not cocoon spinners they can burrow into the soil when they are ready to change to pupae.

     Instead of applying the sticky material directly to the glass a strip of sticky fly paper may be glued to it.

     As a rule the butterfly caterpillar easiest to find lives upon cabbages. Go into the garden and you are likely to see a dozen green caterpillars upon as many cabbage plants. Bring in several of the larger ones and place them in a vivarium with some fresh cabbage leaves. In a few days some of them will be likely to fasten themselves to the vertical sides of the vivarium and shed the caterpillar skin. Each thus becomes a chrysalis. About ten days later this chrysalis skin will break open and a white Cabbage butterfly will come out.

     So your caterpillar goes through the four different stages of insect life. It was first an egg laid upon the leaf by a butterfly; the egg hatched into the caterpillar or larva; the larva changed to the chrysalis; the chrysalis changed to the butterfly or adult insect.

     One of the most satisfactory ways to rear the caterpillars of butterflies is to get the females to lay their eggs upon the food plant. In the case of many species this is not difficult. The simplest way is to enclose the mother butterfly in a small gauze bag tied over the branch of the food plant. If she has eggs ready to deposit she is very likely to lay them under these conditions. After they are laid the mother butterfly may be allowed to escape, but it is well to replace the gauze protection as a safeguard against many sorts of enemies which may destroy the eggs or the young caterpillars that hatch from them. Another way is to enclose the butterflies with a twig of the food plant in a glass jar, sealing it tight to prevent the leaves from wilting. The butterfly is likely after she has quieted down to lay her eggs upon the leaves. According to William G. Wright, who speaks from his long experience with the butterflies of the West Coast, these genera will lay their eggs on anything: Parnassius, Argynnis, Euptoieta, Neonympha, and all members of the family Satyridae. In these cases one can get the eggs by simply enclosing the butterflies in glass jars or gauze nets without even the leaves of the food plant. William H. Edwards found in his long experience that one can get the eggs of practically all butterflies in confinement, provided only the insects are sufficiently mature so that the eggs are ready to be laid. He found that the cause of failure to get eggs from many of the Fritillaries early in the season was that the eggs were not mature and that from the same kinds of butterflies with which he failed early in the summer he got plenty of eggs in September.

     There is here a rich field for observation and experiment for every naturalist who wishes to take up the study of butterflies. He can be sure of the parentage of the caterpillars and can trace them from the very moment of egg-laying through all their wonderful changes until they become butterflies again.

PHOTOGRAPHING BUTTERFLIES

     There is a famous old saying that to make hare stew it is first necessary to catch your hare. So if one wishes to make perfect pictures of butterflies it is first necessary to get the caterpillars. For though caterpillars are not butterflies they are butterflies in the making and they will show you most interesting stages in nature's manufacture of these dainty and exquisite creatures. This is not, however, the chief reason why the photographer should get them. He will wish to make perfect pictures and in order to do this he must have not only perfect specimens but living butterflies which are willing to look pleasant while he makes comparatively long exposures under conditions of light that he can control. If you catch a butterfly outdoors and bring it in you will be likely to find that it is by no means a docile subject. The sunlight shining through the nearest window will be a call which you cannot counteract and your butterfly will constantly respond to it in a most vexing manner. So you must catch the butterfly young and take advantage of a brief but docile period in their lives when they are willing to pose before your camera in quite a remarkable manner. This is the period just after the butterfly emerges from the chrysalis when its wings are fully developed but before the tissues have hardened and the muscles in the thorax are strong enough for flight. At this time the butterfly is perfect, every scale is in its place and every spot of color is at its best, and it will rest quietly upon a flower, leaf, or twig while you adjust the camera and expose the plate. From one such specimen one can get many pictures upon different flowers and with different angles of view. (See plates.)

     In order to make admirable photographs of living butterflies it is by no means necessary to have a regular photographic studio. If one has a room lighted from the north or east one can arrange for exposure near the window, using cardboard reflectors to make the light more even from both sides. In such a situation one soon learns the exposure periods required and can easily get many beautiful photographs.

     A collection of prints of the butterflies of one's locality would be one of the most interesting photographic exhibits that an amateur could select. It is comparatively easy to get rather full sets showing the life-histories of several of our larger species and such sets are of course of especial interest. In the case of those caterpillars which make nests upon the food plant, like the Painted Beauty larva which remains for weeks feeding upon the leaves of the common wild everlasting, the taking of the pictures of the different stages is comparatively easy. One can keep the plant with the stem in water, and get the caterpillar to change to the chrysalis, and emerge as the butterfly, in the nest made from the flower heads and the upper leaves.


From a drawing by W. I. Beecroft            THE BLACK SWALLOWTAIL            Caterpillar, chrysalis and butterfly

Two hundred Monarchs resting on one dead limb

Photographed by Craig S. Thomas
"When a stick was thrown into the tree the air was full of Monarchs"
A MIGRATION OF MONARCH BUTTERFLIES

THE IMPROVED OPEN VIVARIUM

From a photograph from life by A. H. Verrill.
THE CYNTHIA MOTH AND THE COCOON FROM WHICH IT CAME


BUTTERFLY COLLECTIONS

     There are few groups in Nature which offer such advantages to the collector as that of the butterflies. They are easily obtained, easily preserved, and retain their beauty for a long period even under exposure to strong light. They offer opportunities for serious study in which one cannot only review the facts which others have already discovered, but also hope to contribute something of value to the sum of human knowledge.

     The mistake most commonly made by beginners with butterflies, as with other collections, is to undertake too much. Instead of starting on the hopeless task of making a collection of the butterflies of the world, it is much better to start with the intention of making a collection of those of one's own town. In the latter case one can hope soon to attain the desired end and then, if one wishes, it is a simple matter to reach out and make a collection of the butterflies of the state or even of the particular region in which the state is located. The natural limitations for a collection in New England is to make a collection of New England butterflies. There is a splendid example of such a collection on exhibition in the museum of the Boston Society of Natural History. This contains representatives of practically every kind that has been collected in New England, and yet there are less than a hundred species in all. So it is apparent that a local collection should be attainable by any enthusiastic student and the very fact that the number of species is limited adds interest and satisfaction to the pursuit.

     The main value of any collection of objects lies in the point of view of the collector. The most natural point of view for a beginner is that of the local fauna, as indicated in the previous paragraph. Such a collection best serves as a basis for a study of the subject but it may well lead to a broader field through some special phase of scientific interest. Thus while it would be hopeless for most persons to attempt a collection of the butterflies of the world it would be entirely reasonable for one to start a collection of all the species in the world of any given genus or tribe, and such a set of specimens would soon come to possess decided scientific value. Or, instead of the point of view of generic or family relationship, one could take the point of view of special geographical distribution. Thus a collection of all the butterflies found within a certain number of degrees of the North Pole showing the circumpolar butterfly fauna would have great scientific interest.

     There are also various other points of view which could be followed in making a collection. There are already in many of the museums of the world collections of butterflies which illustrate the various phases of true mimicry-the resemblance of one species to another in the same region. This is a field in which one could spend a lifetime of endeavor, and secure results of great value to the world of science. An easier problem for most collectors in the United States would be a collection made from the point of view of resemblance to environment, including such examples as the Angle-wings that show a bark-like set of marks on the under surface. Yet another point of view would be that of hibernation, the making of a collection of all butterflies that hibernate as adults.

     These are only a few suggestions. There are many other phases of butterfly life which could be utilized as the basis for interesting collections. The important thing is to have a definite object in view and to make the collection a basis for a real study of the subject, so that the collector will not only be growing intellectually but will also be making a real contribution to our scientific knowledge.

Collecting Apparatus

     To collect and preserve butterflies in proper condition for study, certain apparatus is necessary. Perhaps the first essential is the collecting net for catching butterflies in the field. The simplest way to obtain this is to buy it of the dealers in entomological supplies. Nets in considerable variety and at various prices are offered in the catalogues of these firms. One can make, however, a net at home with little difficulty. One need only obtain an iron wire about one fifth of an inch in diameter and bend it into a circular ring a foot or fifteen inches wide, leaving the ends projecting at right angles to the circle and having a blacksmith weld them together so as to form a spur about four inches long. Now thrust this spur into some, convenient handle, such as a broomstick, and sew over the wire circle a bag of mosquito netting, Swiss muslin, or some similar fabric. It is better that this material be green or black rather than white.

     After the butterflies are caught, they must be killed, so some form of killing bottle is necessary. Most collectors use a cyanide bottle, in which the fumes of cyanide of potassium kill the insects. One of the best ways to make this is to place in a wide-mouthed bottle two or three lumps of cyanide of potassium, approximately an inch across. Over this place some fine sawdust and on top of the sawdust, pour liquid plaster of Paris carefully so that it will harden into a layer about half an inch thick. Allow the plaster to become thoroughly dry, then insert the stopper into the bottle and it will be ready for use. It is better to use a ground glass stopper so that the bottle will always be air tight. The sawdust is often omitted, the plaster of Paris being poured directly over the cyanide. The special advantage of the sawdust is that it tends to absorb the cyanide in case it liquefies, as it often does in damp weather. As this cyanide is a deadly poison, it is better to let a druggist prepare the bottle or else to buy it already prepared of the dealers in such supplies.

     After the specimens have been killed in the cyanide bottle, some method of keeping them is necessary. The simplest way is to preserve them with their wings closed together in pieces of paper folded over into triangles as indicated on the accompanying diagrams.


Butterfly Envelopes: Fold first on line AB; then on AD and
CB; then on BF and EA (From Holland)

     Such specimens may be kept for an indefinite time and if one wishes to mount them later, it is only necessary to place them for a few hours in a relaxing jar, which is simply a closed vessel with enough water in the bottom to saturate the air with moisture. A great advantage of keeping the specimens in these paper covers is that they require so little room and are easily stored away in tin cans or boxes. There they are safe from dust and destroying enemies.

     Those butterflies which are to be preserved in the ordinary way, in drawers or cabinets, must be spread out and held in position while the body is drying so that the wings will remain expanded. For this purpose, some form of a setting board is necessary. These may be bought of dealers or made at home. One of the simplest kinds consists of two thin strips of pine board, a foot or more long, nailed to end pieces with a space between the two boards wide enough to accommodate the bodies of the butterflies. Beneath this open space, a piece of thin cork is tacked. The pin on which the butterfly is fastened is pushed through the cork until the wings of the insect are level with the boards. The wings are then brought forward with a needle point until they are in the desired position and they are then held in place by pieces of glass or by bits of cardboard fastened down by pins. The butterflies must be left in this position until thoroughly dry.


Setting Board with Butterfly in place. (from Holland)

     Special insect pins should be used for butterflies. These are longer than common pins and have rounded heads. They are offered for sale by entomological dealers. Instead of pinning the insects and preserving them in cabinets, one may keep them in the Riker mounts, which have the advantage of being sealed so that there is no chance for dust or museum pests to reach the specimens. If one wishes to collect extensively, one will need a considerable number of setting boards and it will be worth while to prepare for them a special drying box like that shown in the picture above.

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(1) Popular Science Monthy, 1898, "A Game of Hide and Seek." Reprinted in the Insect World, 1899.

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