Butterflies Worth Knowing Part 17

This beautiful b.u.t.terfly is one of the most distinctive of all our species. It is of moderate size, its wings rarely expanding more than two inches, and it has sufficiently irregular outlines to indicate its relations.h.i.+p with the Angle-wings. The most striking feature of the upper surface is the broad band of orange-brown extending clear across both wings a little inside the border. The remaining surface is a darker brown marked with two orange-brown spots near the front margin of each front wing and having scattered iridescent scales which show plainly under a lens. The suggestion of the coloring of a tortoise-sh.e.l.l is easily seen in these rich brown tones. The under surface is a wonderful ill.u.s.tration of protective coloring. With wings closed and resting against the bark of trees or lying beneath the trees among fallen leaves, it would require a keen eye to detect the insect. (_See plates, pages 160-161._)

The American Tortoise-sh.e.l.l is distinctly a northern species. North of lat.i.tude forty-three degrees it seems to occur practically from ocean to ocean, extending far up toward the arctic region. It is commonly found in British America as far north as Fort Simpson in lat.i.tude sixty-one degrees. There are specimens in the British Museum collected by the explorer Ross in arctic America, and there are many in our own National Museum collected in the Hudson Bay region by various American explorers. In New England the species is abundant at times in New Hamps.h.i.+re, Vermont, and Maine. In the vicinity of New York City and Buffalo, New York, it is rather rare. And south of this lat.i.tude it is found chiefly at the higher elevations in mountainous districts. As a rule it is likely to vary in numbers from year to year, sometimes being extremely abundant while more commonly it is rather rare. These are the same sorts of fluctuations that we find in the case of the Mourning-cloak, the American tent caterpillar, and various other insects whose larvae live in colonies. The variation is probably due to the fact that when the caterpillars become unusually abundant they become correspondingly conspicuous and so provide a s.h.i.+ning mark that is soon discovered by their insect enemies or by various fungous diseases.

_The Story of Its Life_

In its manner of laying eggs this b.u.t.terfly differs from most others.

The great majority of our familiar species lay their eggs one in a place or possibly two or three near together. Some species deposit several in a group, while some, like the Mourning-cloak, may lay two or three dozen in a cl.u.s.ter. Very few, however, deposit hundreds in a bunch. Two of these are the Baltimore and this American Tortoise-sh.e.l.l. In the case of the latter the eggs are loosely laid, hundreds together, upon the leaves of the common stinging nettle.

Probably each female can deposit six or eight hundred eggs. In less than a week the eggs hatch into minute blackish caterpillars that feed upon the tender tissues of the leaf upon which they were born and then migrate together toward the top of the plant. In their habits they are quite similar to the caterpillars of the Mourning-cloak. As each walks it spins from its mouth a silken thread and the combined effect of hundreds of these threads is to make a noticeable silken web over the leaves. The caterpillars remain in colonies, feeding together from day to day and gradually denuding the upper branches of the nettle plant, leaving an unsightly silken web as a memento of their presence. This webbing is very suggestive of the similar result left behind by a colony of Mourning-cloak caterpillars upon the twigs of elm or poplar.

When about half grown these caterpillars are likely to scatter more or less in accidental groups which may make small shelter tents from the larger leaves. In each little nest there may be four or five or more of the dark-colored caterpillars. From these shelter tents they sally forth to feed upon the adjacent leaves and a little later become full grown as caterpillars. Each now wanders away and finding such shelter as it is able to, spins a b.u.t.ton of silk and becomes a chrysalis. It remains in this condition but a short time before it emerges again as the beautiful b.u.t.terfly.

This species is commonly reputed to have three broods a year, hibernating both as a b.u.t.terfly and as a chrysalis. It has been suggested, however, by Mr. W. F. Fiske, one of our most painstaking entomologists who has studied the b.u.t.terflies of New Hamps.h.i.+re for many years, that it is more probably double-brooded with a period of aestivation during the later weeks of summer. This seems a very probable condition and it is to be hoped that some observer will make such a careful study of this species as to settle the point definitely.

In the case of many b.u.t.terflies the distribution of the species coincides with the distribution of the food plant. This American Tortoise-sh.e.l.l, however, is perhaps the exception that may prove the rule, for its southward limit is far north of the southern range of the stinging nettle. Evidently, it is a species which has developed in adjustment to the cool climate of northern regions or high alt.i.tude, and it does not easily adapt itself to a warmer territory.

=The White-J b.u.t.terfly or Compton Tortoise= _Eugonia J-alb.u.m_

During bright days in March and April one is likely to find two kinds of b.u.t.terflies on the wing in open glades of the woods. One is the familiar Mourning-cloak and the other is the Compton Tortoise--the latter generally much less abundant than the former. Both make the most of the brief periods of suns.h.i.+ne and quickly disappear when the sky is overcast.

The Compton Tortoise b.u.t.terflies which are thus abroad in early spring have been in hibernation since October. They are helping to carry the species over from one season to another, and as the days become longer and warmer they appear on the wing more and more, seeking such liquid food as the field and forest yields during the days of early spring.

The sap exuding from holes in bark made by woodp.e.c.k.e.rs, or from the tappings of the maple trees by man, the nectar of willow catkins, the moisture of roadside pools--these help to yield a precarious sustenance to these b.u.t.terflies after their long winter fast. They remain upon the wing week after week, while spring slowly progresses in the northern regions they inhabit. When at last the leaves push out on their food trees--willow, birch, and elm--the females lay their eggs and then, having lived to what for a b.u.t.terfly is a ripe old age, they die, after nearly ten months of adult existence.

Apparently the eggs are laid in cl.u.s.ters on the twigs, although this seems to be one of the many facts about b.u.t.terflies awaiting observation by some careful student. The caterpillars feed together in small colonies but make no nest. They become full grown in about a month. They are then nearly two inches long with spinous, greenish bodies, striped with lighter lines. Some change to chrysalids about the middle of June and ten days later change again to b.u.t.terflies, the first of which appear early in July while others continue to emerge for nearly a month.

These b.u.t.terflies may be seen rather frequently from midsummer on, visiting various flowers and sipping the juices from decaying fruits beneath the trees. At times they seem to disappear in August to reappear in October, a fact which has led some observers to suggest that there is a second brood. The caterpillars of this brood, however, have never been observed and a much more probable explanation has been made by Mr. W. F. Fiske who studied the b.u.t.terflies of New Hamps.h.i.+re carefully for many years. He found that in the hot summer weather this b.u.t.terfly goes into a seclusion similar to that of its winter rest--that is, it aestivates in summer and hibernates in winter. "The possibility that the October J-alb.u.m did not represent a second brood," writes Mr. Fiske, "was rendered almost a certainty by repeated observations which failed to disclose a single specimen approximating in freshness to average August individuals, and the question of their whereabouts during the interim was unexpectedly answered one warm August day by my finding several snugly packed away under the s.h.i.+ngles on an old roof. The theory of the aestivation of the b.u.t.terflies of this group will explain a good many points. .h.i.therto obscure in the life histories of the other species."

In October these b.u.t.terflies seek their winter quarters, finding them in woods and groves. Apparently they commonly rest upon the bark of the trunk as well as crawl into such crevices beneath loose bark as they can find. Here they remain through fall, winter, and spring, except when called into brief periods of activity by the unwonted warmth of the winter suns.h.i.+ne. Then in spring they come forth again to lay the eggs for the caterpillars of the new generation.

The fresh b.u.t.terflies are creatures of exquisitely modulated coloring.

The name Compton Tortoise has reference to the rich brown tones of the upper wing surface, suggestive of those of fine tortoise-sh.e.l.l. In fresh specimens much of the surface, especially in the middle and along the front border, is overlaid with iridescent purple scales.

Near the front outer angle of each of the four wings there is a distinct white spot, divided near the middle by a darker line of the vein running through it. The under surface is one of the best examples of mimicry of gray bark to be found in any b.u.t.terfly. The tones vary considerably in different individuals, but in all the protection must be well nigh perfect when the insect is at rest with closed wings upon the bark of a tree. The striking angularity of the wing's border doubtless helps to conceal it, and the habit of dropping motionless to the ground when disturbed must also have protective value. Near the middle of each hind wing there is a small white J which led to the specific name _J-alb.u.m_.

This b.u.t.terfly is essentially a member of the Canadian fauna. It ranges from far north in Labrador, British America, and Alaska, south as far as Pennsylvania, but toward its southern limit it occurs only on the higher elevations of mountains like the Alleghanies.

=The Buckeye= _Junonia coenia_

Some genera of b.u.t.terflies seem to belong almost exclusively to the north temperate regions, seldom occurring even in our Southern states.

Others belong equally exclusively to tropical regions, seldom straying into the north. The Buckeye is an ill.u.s.tration of the latter group. The genus Junonia to which it belongs is essentially tropical, as it contains several species which are found throughout the tropics in both the Old and the New Worlds. In fact, this is apparently the only species which occurs north of the tropics. It has an extraordinary range, being found from Cuba to Ma.s.sachusetts and from the Atlantic to the Pacific coasts. Toward the northern limits of its range it is very rare and one of the greatest prizes which the collector can obtain. In our Southern states it is an abundant and generally distributed b.u.t.terfly and, as it hibernates as an adult and one group follows another throughout the season rather rapidly, it is likely to be taken at almost any time. (_See plate, page 176._)

The mother b.u.t.terflies select as food plants for the larvae various members of either the plantain or figwort families. They lay eggs, one in a place, upon the leaves of plantain, figwort, gerardia, and related plants generally near the tip of the leaves. Less than a week later these hatch into spiny caterpillars which feed upon the green substance of the leaves during the next few weeks. For the most part they eat between the veins leaving a ragged effect which may help in finding them. When full grown they change to chrysalids which hang straight downward and bear a general resemblance to those of the Thistle b.u.t.terfly. Curiously enough, those chrysalids which are attacked by parasites take on a characteristic golden hue; although the normal healthy chrysalids are dark brown with a few touches of a decidedly lighter brown.

In its tropical home, where there is no winter period to interrupt its growth, this b.u.t.terfly doubtless continues to develop generation after generation without any break in the sequence. As the species goes north, however, there is necessarily such an interruption--in which case the winter seems commonly to be pa.s.sed by the adult b.u.t.terfly. In our Southern states there are commonly three or four broods each year, while in the northern parts of its range there is but one brood a year. In the South there is such an overlapping that all stages of the insect may be found at one time.

_Synopsis of the Angle-wings_

_I. The Polygonias_

The most angular of the Angle-wings are grouped in the genus Polygonia. They are characterized by having the outer margin of the front wings projecting in two places in a way to give an angular effect, and by having the hind or inner margin distinctly excised toward the outer end, so that this margin is curved rather than straight.

_Violet-tip_ (_Polygonia interrogationis_ or _Grapta interrogationis_). Expanse 2 1/2 inches. Under surface of each hind wing marked by a silvery semicolon, made up of a dot and a crescent.

_Hop Merchant_ (_Polygonia comma_ or _Grapta comma_). Expanse 2 inches. A white comma with expanded tips on lower surface of each hind wing. Lower surface of all the wings mottled with brown.

_Green Comma_ (_Polygonia faunus_ or _Grapta faunus_). Expanse 2 inches. A white comma with expanded tips on lower surface of each hind wing. The lower surface of all the wings more or less mottled with green toward the margins.

_Gray Comma_ (_Polygonia progne_ or _Grapta progne_). Expanse 2 inches. A white comma with tips narrowed rather than expanded on lower surface of each hind wing.

_II. The Vanessids_

Our beautiful species of the genus Vanessa may be known by the long scales that make up the fringe on the wing margins, in alternate groups of black and white. There are also several white spots on the upper surface of the outer angle of each front wing.

_Red Admiral_ (_Vanessa atalanta_, _Pyrameis atalanta_ or _Cynthia atalanta_). Expanse 2 inches. Upper surface of front wings blackish, marked with white spots on outer angle and a broad orange stripe across the middle.

_Painted Beauty_ (_Vanessa huntera_, _Pyrameis huntera_ or _Cynthia huntera_). Expanse 2 1/2 inches. Upper surface orange-brown with black, white, and blue markings. Lower surface of each hind wing with two large eye-spots, each extending across two veins.

_Painted Lady_ or _Cosmopolite_ (_Vanessa cardui_, _Pyrameis cardui_ or _Cynthia cardui_). Expanse 2 1/2 inches. Easily distinguished from the Painted Beauty by the four or more small eye-spots on the lower surface of each hind wing, each eye-spot being included between two veins.

_III. Other Angle-wings_

The other common Angle-wings are readily distinguished by the following characters:

_Mourning-cloak_ (_Euvanessa antiopa_ or _Vanessa antiopa_). Expanse 3 1/2 inches. Easily known by the nearly black wings with creamy white borders.

_American Tortoise-sh.e.l.l_ (_Aglais milberti_ or _Vanessa milberti_).

Expanse 1 1/2 inches. One of the smallest of the Angle-wings. Easily known by its small size and the broad orange band extending across the upper surface of all the wings just beyond the middle. Under surface dark mottled gray without distinct white markings.

_Compton Tortoise_ (_Eugonia j-alb.u.m_, _Vanessa j-alb.u.m_ or _Grapta j-alb.u.m_). Expanse 3 inches. Best known by the straight line of the inner margin of the front wings and the white j on the under side of each hind wing.

_The Buckeye_ (_Junonia coenia_ or _Vanessa coenia_). Expanse 1 3/4 inches. Distinguished by the large eye-spots on the upper surface of the wings, one on each front and two on each hind wing. Eyes not hairy.

THE TRIBE OF THE SOVEREIGNS

No other small group of American b.u.t.terflies has attracted so much attention as the species of the genus Basilarchia, which have been happily called the tribe of Sovereigns. These are rather large b.u.t.terflies with rounded wings which are found in one species or another over practically the whole of North America. Some of them are of exceeding beauty and all of them present life-histories of extraordinary interest. At least two of the species are the most notable examples of the mimicry of other b.u.t.terflies that are shown in our fauna. They also present some extremely interesting problems for the study of natural hybrids and they ill.u.s.trate in their development some of the most wonderful cases of adaptation to environment that have ever been found.

[Ill.u.s.tration: _From a drawing by W. I. Beecroft_ _See pages 268-282_

SOME COMMON SKIPPERS