Butterflies - The Swallowtails Continued
( Originally Published 1917 )
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 back-ward 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 salis; 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 t likely to begin to appear early in August, continuing to be-come 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
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 deter-mined the precise condition.
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 m 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 cater-pillar 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:
"When I recall the first sight of this larva, the impression gained of it was a most curious one. The forward mask like face was remarkably startling. This mask, bearingeye like spots and the light transverse ridge, gave it an aspect which might easily be mistaken for real eyes and a mouth. This contrivance is only a false face in no way connected with the real eyesand mouth. One might imagine the shock that a bird, or other predaceous enemy, would experience when looking upon this grinning mask. This is in reality the effect produced, for I have seen small birds so alarmed that they lost their appetite and curiosity for these larvae after a brief glance at them. It is certain that these singular markings have the effect of terrifying their bird enemies."
The yearly cycle of the Tiger Swallowtail is much like that of the related species. It passes the winter as a chrysalis, the butterflies coming forth just about the time that the lilacs bloom. They remain upon the wing for a few weeks and deposit their eggs upon a great variety of trees and shrubs, for the food plants of the larvae are unusually varied and include tulip trees, birches, wild cherries, apples, poplars, ash, and several other common trees or shrubs. These eggs soon hatch into caterpillars that feed upon the leaves and make for themselves resting places by spinning a web of silk transversely across the surface of the leaf. They remain upon these silken webs when not feeding and in later life are likely to cause the leaf on which the web is made to curl into a partial tube. When fully developed they change to chrysalids which give forth the summer brood of butterflies in July and August. These in turn lay eggs for the caterpillars which change to chrysalids in autumn and remain in that condition until the following spring.
The Short tailed Papilio
Were one enough of a magician to make one butterfly over into another it would be comparatively easy to take a Black Swallowtail and transform it into this species. One would only need to trim off the long tails so that they project very slightly from the angles of the hind wings and to change the yellow spots to orange. He would thus accomplish what Nature through the long ages seems to have accomplished in a limited northern area in Newfoundland and around the Gulf of St. Lawrence, for the Short tailed Papilio is confined chiefly to this region, where it lives a life very similar to that of the Black Swallowtail. The caterpillar feeds upon the leaves of various members of the parsley family and is said to have learned to warm itself during the middle of the day by resting upon stones and gravel which have absorbed the sun's heat rays. Presumably there is but one brood a year and the insect hibernates as a chrysalis.
The Palamedes Swallowtail
If the magician who had succeeded in converting a Black Swallowtail into the Short tailed Papilio wished to try his hand on making a Palamedes Swallowtail he could not do better than to use again the same black butterfly. He would only need to make it about one half larger, retaining practically all its color markings and the outline of its wings and tail. For this species bears a remarkable re-semblance to the Black Swallowtail, seeming to be a giant variety induced by the warmth' of the southern climate where it lives, and possibly by the more generous supply of the magnolia and sassafras leaves upon which the caterpillars feed.
This species is distinctly a southern form occurring as far west as the Mississippi River throughout the more Southern states. As one would expect in the long seasons and warm climate of this region there are several broods each year and the caterpillars often hibernate as well as the chrysalids. The adult butterflies are lovers of the sun and are said to roost at night upon the tops of live oak and palmetto trees.
The Zebra Swallowtail
Most of our Swallowtail butterflies are so distinctive in form and colors that they are easily distinguished from one another, but the Zebra species is so different from all the rest that when it is once seen it is likely always to be re-membered. The striking combination of green and black stripes with very long tails, set off by beautiful crescents of blue and of red, at once distinguishes this fine butterfly in any of its varying forms.
Three distinct forms of this species occur, namely: Marcellus, the early spring form, small in size with short tails, that show white only on the tips;
Telamonides, the late spring form, somewhat larger, with tails a little longer and showing more white on the outer half;
Ajax, the summer form, decidedly larger with tails very long.
It would be a comparatively simple matter to understand these forms if they were simply seasonal variations, with three broods, each form succeeding the other as the season advances. But this is far from being the case. We have instead the most complicated and confusing series of conditions imaginable conditions for which no one has yet given satisfactory explanations.
To make a fairly clear statement of what happens, suppose we assume that we start with twenty over wintering chrysalids. In April ten of these disclose their butterflies which are Marcellus, the early spring form. In May the other ten disclose their butterflies which are Telamonides, the late spring form. We thus have these two forms appearing successively in spring from the same set of over wintering chrysalids.
After flying about for a short time the Marcellus or early spring Swallowtails lay eggs upon the leaves of papaw trees or bushes. These eggs soon hatch into caterpillars that feed upon the leaves and grow rather rapidly.
A little more than a month later they mature into butter-flies which are Ajax, the summer form.
In a similar way the Telamonides or late spring butterflies lay eggs soon after they appear, also upon papaw leaves, and these eggs in about a month mature into Ajax, the summer form.
So we have Ajax, the summer form, developing directly from both the early spring or Marcellus and the late spring or Telamonides butterflies.
These Ajax butterflies in their turn lay eggs for caterpillar young. These soon mature into a brood of butter-flies which are of this same Ajax form. There may be successive broods through the summer, practically all of them being this same Ajax summer form.
The last brood of caterpillars, however, change to chrysalids which do not disclose the butterflies until the following spring. And then the first that come out are the Marcellus form and the last the Telamonides form. So we may have these two forms maturing from the same brood of autumn caterpillars.
This seems a sufficiently complicated life-history to suit the most persistent solver of puzzle problems, but there is an additional factor which adds much to the possible con sion of the broods. In each brood of caterpillars from the earliest to the latest there are a certain number of chrysalids which remain dormant through the remainder of the season and the following winter, maturing into butterflies the next spring. Consequently at the end of every winter there are a miscellaneous lot of chrysalids which represent every brood of caterpillars that lived the previous season, and all of these develop into either Marcellus or Telamonides butterflies.
Such a condition of affairs certainly represents what an old New Englander would be likely to call a "mixed-up mess," and it is difficult for science to find rhyme or reason to explain it. It speaks eloquently for the perseverance of W. H. Edwards that he was able with infinite patience through years of study and experiment to untangle this intricate web of butterfly existence.
While the preferred food plant of this species is papaw, the caterpillars are also known to feed upon the spice bush and upland huckleberry. When full grown these eater-pillars are about two inches long and of a general pea-green color, banded transversely with yellow and black, and having an especially conspicuous band of this sort on the third ring behind the head. The scent organs are protruded when the larva is disturbed and emit an offensive odor. The chrysalis are green or brown according to the surroundings.
The Zebara Swallowtail is a southern butterfly found as far west as Texas and the Rocky Mountains and having its northern limits in a zone ranging approximately from Massachusetts to Nebraska. It is especially abundant in the Southern states east of the Mississippi River.
Mr. S. F. Denton found this species abundant in south-ern Ohio where the females laid their eggs upon the small papaw bushes. They selected the leaves of these bushes for sleeping quarters, "clinging to the under side of the leaves where early in the morning they might be taken with the fingers."
Synopsis of the Swallowtails
Tiger Swallowtail: Yellow form (Papilio glaucus turnus). Expanse 31/2 to 5 inches. Upper surface of wings bright yellow with each black margin marked with a row of yellow spots. Both sexes throughout its range. Black form (Papilio glaucus glaucus). Black all over with blue markings on outer half of hind wings and row of straw-yellow crescents on borders of same. Females only, and only south of about latitude 40 degrees.
Giant Swallowtail (Papilio thoas or Papilio cresphontes).
Expanse 4 to 5 1/2 inches. Upper surface black with two bands of yellow starting at the inner margin of the hind wings and coming together as a row of yellow spots at the outer angles of each front wing. A yellow spot on each black tail. Under surface yellow.
Zebra Swallowtail. Expanse 3 to 3 inches. Easily known by the stripes of green upon black and the long, slender tails. The different forms vary in size and in the length of the tails. Scientific names are: Early Spring Form, Iphiclides ajax marcellus Late Spring Form, I. ajax telamonides; Summer Form, I. ajax ajax.
Green-clouded Swallowtail (Papilio troilus). Expanse 31 to 4 inches. Black with about seven yellowish spots, on outer margin of each front wing and eight marginal spots on each hind wing, those at the ends of row orange, the rest yellowish or bluish. Outer half of hind wings clouded with greenish blue. Under surface black with two distinct rows of yellowish spots on front wings and two rows of orange spots on hind wings.
Blue Swallowtail (Laertias philenor, often called Papilio philenor). Expanse about 4 inches. Black or brownish black with most of hind wings showing a bluish green iridescence. A row of marginal spots on each hind wing, more or less distinct on the front wings. Outer fringe with broad white markings interrupted by black ones. Under surface of each hind wing with seven large orange spots, some with partial borders of white.
Black Swallowtail (Papilio polyxenes or Papilio asterias). Expanse about 3 inches. Black with. two conspicuous rows of yellow spots on outer half of wings, more distinct in males. On hind wings rows of blue spots or splashes between the yellow ones. Orange-red circle with black centre at inner angle of each hind wing. Under surface with markings more distinct and more orange yellow.
Short tailed Swallowtail (Papilio brevicauda). Much like the Black Swallowtail but generally smaller, with very short tails, and with the yellow markings more or less changed to orange. Confined to the limited region of Newfoundland and the lands bordering the Gulf of the St. Lawrence.
Palamedes Swallowtail (Papilio palamedes). Expanse 4 to 4 1/2 inches. Much like the Black Swallowtail but considerably larger. A curved yellow line on the head back of each eye. Found only in the South.