Butterflies Worth Knowing

by Clarence Moores Weed

The Eclosion of the Butterfly

The transformation of a chrysalis into a butterfly is always one of extraordinary interest. Comparatively few definite descriptions of this process have been given by careful observers. One of the best of these is that written by Mr. Scudder in connection with the emergence of this butterfly, and it is so accurate and complete that it seems worth while to quote it at length:

"The butterfly generally emerges from the chrysalis early in the day," writes Mr. Scudder, "and the first signs of the immediate change are strong forward and backward movements of the chrysalis at intervals of a few seconds; perhaps the third or fourth attempt will be successful, when a click may be heard at the distance of several feet; but all the subsequent movements are absolutely noiseless, though rapid; at intervals of three or four seconds, spasmodic movements similar to the first carry on the process; first the split continues along the thorax; then it runs down either side between the legs and wings, ultimately to the tips of the antennae. As this progresses, the actions become more strenuous and more frequently repeated; with eager efforts the butterfly pushes forward its half-detached head; now an antenna springs from its case, at once assuming its natural attitude; the other soon follows, and then the wings are partially drawn from their sheaths, and while in this position seem to be used as levers or arms to aid in withdrawing the rest of the body; next the legs appear, seize the upper part of the chrysalis skin, and speedily withdraw the whole body. It is now a curious-looking object, the wings wrinkled and bloated, and, although the whole process of escape lasts little more than half a minute, already twice the size of the sheaths they lately occupied. The insect crawls upward until it finds a secure resting place, and there remains until ready for flight; each half of the tongue, drawn independently from its receptacle, is rolled in a separate spiral, and now while the wings are gradually expanding the insect applies all its energies to uniting their two parts, incessantly rolls and unrolls them, and beginning simultaneously at the base, gradually fits them together by their interlocking joints; in about fifteen minutes all but the tips are perfectly united; these require nearly fifteen minutes more, and are not fairly interlocked until the wings are fully expanded, nearly a full half hour after the escape from the chrysalis; the wings, however, are still tender, and generally require two hours to stiffen. When at last the insect ventures upon flight, it is not with an uncertain flutter, but boldly and steadily, as if long accustomed to the action."

The butterflies of this second brood of the season are likely to begin to appear early in August, continuing to become more abundant throughout that month. These lay eggs upon the same food plant and the caterpillars grow to maturity in the same way as those of the first brood. They become full grown during September or October, and then change to chrysalids which remain dormant until the following spring. The species thus has two broods each year and passes the winter only in the chrysalis state.

These beautiful butterflies are likely to be found in the sort of situations where the food plants of the larvae are growing. Open groves, the borders of woods, and the margins of streams or marshes are the places where one is most likely to find spice bush and sassafras. These are the places to look for these butterflies which one may often see in graceful flight near the ground, pausing now and then to seek a sassafras leaf or to sip the nectar from a flower.

The Tiger Swallowtail
Papilio glaucus

One of the many things that make a study of the life-histories of butterflies of great interest is the variations in the development of many of the species. One who follows the simplest life-story of a butterfly and sees the egg change to larva and the larva change in size and form and color with each successive moult and then change again into the seemingly inert chrysalis, from which there finally comes the winged butterfly—unlike the egg, unlike the larva, unlike the chrysalis—a creature of perfect beauty, wonderfully adapted to living freely in the air and sipping ambrosial nectar from the flowers—one who follows these changes with awakened vision can scarcely fail to have a sense of wonder as to the laws that govern such intricate phenomena. But the marvel is still more pronounced in the case of those butterflies which have two or more forms arising from the same lot of eggs in a way which science has as yet not adequately explained.

The splendid Tiger Swallowtail is an example of this dimorphism which is of especial interest because of the fact that the extra form is confined to one sex and to only a part of the geographical area over which the butterfly is found. The species occurs over a very large part of the North American continent, being found from ocean to ocean and from Canada to Florida. In the region north of approximately the fortieth degree of latitude there is but one form of the insect—the familiar yellow-and-black striped butterfly which every one has seen visiting the lilac blossoms in May or June. South of this, however, part of the females take on an entirely different appearance, being almost wholly black with the hind wings touched with lines of blue and bordered with crescents of yellow and orange. The curious thing about it is that a certain mother butterfly may lay a dozen eggs part of which will develop into the usual yellow form and the rest into the black form, both lots being of the same sex. This black form is so entirely distinct in appearance that the two were originally described as separate species, and they were long considered such, until breeding experiments determined the precise condition. (See plate, [page 17].)

This species is of interest also for another reason. The caterpillars during their later life are remarkable examples of that curious resemblance to the head of a serpent which is thought to have a real protective value in frightening away attacking birds and possibly other enemies. The rings of the body just back of the head are much swollen and on the top of the swollen part there are two large circular marks which bear a striking resemblance to eyes. When the insect is at rest it withdraws its head and holds up the front of the body in such a way as certainly to suggest at the first glance that one is looking at the head of a small snake, an impression which is likely to be enhanced when the caterpillar pushes out the curious yellow scent organs from the ring near the top of the head, these organs taking on the forked appearance of a snake's tongue.

Obviously it is exceedingly difficult to get definite observations under natural conditions to determine whether these seeming resemblances are really of value to the caterpillar in frightening away birds or other enemies. About the only direct evidence which I have come across upon this point is found in this paragraph by Dr. J. L. Hancock: