Butterflies Worth Knowing Part 14

Farther south, in southern New England, the life-history is more definitely two-brooded each year, as already described in an earlier paragraph. Still farther south, in the region of the Virginias, it is definitely three-brooded, there being at least two summer broods during the year. How is it that the instinct to become lethargic lies dormant in the summer broods of caterpillars and shows itself only in the autumn brood? Is it perhaps due to a reaction to the colder nights of the later season? If so, possibly one could get interesting light upon the subject by experimenting with placing the summer caterpillars temporarily in an ice chest.

_Synopsis of the Crescent-spots_

_Baltimore Checker-spot_ (_Euphydryas phaeton_ or _Melitaea phaeton_).

Expanse 1 3/4 inches. General color purplish black with the upper surface marked thus: a marginal row of red-brown spots between the veins; two rows of creamy yellow spots inside of the row just mentioned; two or three small red and two or three small white spots near front border of each front wing. Under surface checkered in red-brown and creamy yellow on a blackish background.

_Harris's Checker-spot_ (_Cinclidia harrisii_ or _Melitaea harrisii_).

Expanse 1 3/4 inches. This species bears a close general resemblance to the Silver Crescent. It may be distinguished by the fact that the middle joint of each palpus is of uniform size from end to end instead of tapering toward its outer end. The tibial joint of the first pair of legs of the male b.u.t.terfly is very thick. The upper wing surface is so marked with black that the tawny red coloring shows only in the middle.

_Silver Crescent_ (_Charidryas nycteis_, _Melitaea nycteis_ or _Phyciodes nycteis_). Expanse 1 3/4 inches. This species may be known from Harris's Checker-spot by the fact that the middle joint of each palpus tapers from the middle to the tip and that the tibia of each front leg in the male is slender rather than stout. On the lower surface of the wings there is a narrow yellowish marginal line.

_Pearl Crescent_ (_Phyciodes tharos_ or _Melitaea tharos_). Expanse 1 1/2 inches. General color much lighter than either of the preceding.

Terminal joint of each palpus less than a third as long as the middle joint.

THE TRIBE OF THE ANGLE-WINGS

The special characteristic that distinguishes the members of this important group from the other Nymphs is the fact that on that portion of the club of each antenna which has not hairs there are three longitudinal ridges. The tribe includes a large number of our most familiar b.u.t.terflies. Nearly all of them are rather large, with bright attractive colors. They fly freely along roadsides and in orchards, fields, and meadows so they are commonly seen by every one.

=The Violet-tip= _Polygonia interrogationis_

The Violet-tip is one of the largest of the Angle-wings, as well as one of the most beautiful of all our species. It has a wonderful violet iridescence which is especially marked on the projecting tip of the hind wing. On fresh specimens, however, it may be seen practically all over both surfaces of the wings and in bright sunlight gives them a sheen of remarkable beauty. The expanded wings measure nearly two and a half inches, the upper surface being marked with dark brown upon a ground of orange-brown. The under surface has a bark-like effect in brownish gray brought about by rather indefinite markings of varying tone. The most characteristic feature is a distinct silver semicolon on the middle of the under surface of each hind wing. This marking closely resembles the Greek interrogation point and so the species was given the specific name _interrogationis_ by Fabricius early in the history of science. It has since often been called the interrogation b.u.t.terfly as a translation of its Latin name, but in as much as the marking on the wings is not at all like the English interrogation point, this has led to considerable confusion and people have considered it a misnomer. It has also been called the Semicolon b.u.t.terfly which is correct enough so far as this most characteristic feature is concerned; but it leads to confusion in connection with the Latin name. The recent practice seems the better, which is to call it the Violet-tip b.u.t.terfly.

_Life-history_

The life-history of this b.u.t.terfly is much like that of the related species. Briefly summarized, this is its story:

The adult b.u.t.terflies, more or less worn and faded from their long hibernation, appear in fields and pastures in May. They fly for several weeks sipping nectar from many kinds of spring flowers. The females search for the leaves of the elm, hop, nettle, false nettle, and perhaps other related plants on which they deposit their ribbed eggs either singly or in small groups, it often happening that one egg will be laid directly on top of another. About a week later the eggs hatch into small spinose caterpillars which begin feeding upon the leaves near by. They continue to feed and grow rather rapidly until they become full size. Each then fastens a bit of pink silk to the stem of the plant or some other support, in which it entangles its hind legs and hangs downward to become a chrysalis which is remarkable for its numerous protuberances and the beautiful silvery and golden spots along the middle of the back. Within these chrysalids the change from larva to b.u.t.terfly takes place, usually in less than two weeks, so that this new brood of adults appears on the wing early in July.

Eggs are laid by these for a second brood of caterpillars that feed upon the host plants in the same way as the others, and mature as b.u.t.terflies late in August or early in September. These b.u.t.terflies visit the fall flowers and suck the juices of fallen fruits, until the cold weather of autumn warns them to seek shelter for the winter. They now find crevices within the bark of trees or places in hollow logs or stone piles or other similar situations, where they close their wings together, so that only the bark-like under surface shows, and remain quiet for long periods. They hibernate in this way, coming forth again the following season to start the cycle for the new year.

In regions where hops are grown commercially the chrysalids of these b.u.t.terflies are often called "hop merchants." There is a quaint fancy that the price of the crop varies with the l.u.s.tre of the golden spots upon the chrysalids. When these stand out conspicuously, according to this fancy, the hops are to sell high--bringing much gold to the owners. When these are inconspicuous the hops are to sell at a low price, with a corresponding diminution in the returns. But this fancy does not apply at all to the chrysalids when they are nearly ready to disclose the b.u.t.terfly, for at this time they lose their metallic l.u.s.tre.

=The Hop Merchant or Comma= _Polygonia comma_

There are two species of b.u.t.terflies which commonly lay their eggs upon the hop and which resemble each other so closely in their earlier stages that they are frequently confused by ordinary observers. One is the Violet-tip or Semicolon and the other is the one which has long been called the Comma. The chrysalids of both are marked in silver and gold and the variation in the golden l.u.s.tre has led hop growers to deduce from them the probable price of hops. On this account the chrysalids are commonly called Hop Merchants and the name has been transferred to the b.u.t.terflies themselves. (_See plate, page 144._)

The Comma is easily distinguished by the conspicuous silver mark in the middle of the under side of each hind wing. This bears a striking resemblance to a comma, hence the name. The b.u.t.terflies are somewhat smaller than the Violet-tips and show to a remarkable degree the angularity in the borders of the wings. The under side is cleverly marked in imitation of the bark of trees, which is doubtless of much benefit to the species in eluding observation during the long months from October until April, when the b.u.t.terflies are hibernating in such concealed shelter as each happens to find. The crevices beneath loose bark, the openings in fallen logs and hollow trees, the inters.p.a.ces in stone piles, as well as the interior of buildings, all serve this purpose.

Like the other over-wintering b.u.t.terflies, the specimens that come forth in spring are commonly faded and more or less frayed from their long wait since bursting forth from the chrysalis. They may often be seen sunning themselves on bright days in April and May, resting upon stones or logs in sheltered spots with their wings fully expanded to receive the greatest benefit from the rays of sunshine.

[Ill.u.s.tration: Eggs laid in string-like cl.u.s.ters on the under side of leaf. Magnified. (From Holland)]

When spring has sufficiently advanced for the leaves of the elm and the hop to be fairly well developed, the mother b.u.t.terflies lay their eggs in a curious and characteristic fashion. Under a lens these eggs look like tiny barrels with vertical ribs. They are deposited in columns, the egg first extruded being attached to the leaf, generally the under surface, and those which follow are placed one upon the other sometimes to the number of six or eight, the group thus making a miniature column. Now if the egg which was first laid should hatch before the others, when the little caterpillar came out it would be very likely to cause the others to fall off and when they hatched they would find themselves in what would be to them an impenetrable forest of weeds and gra.s.ses from which there would be small chance to escape to reach the elm or hop leaves. To avoid this calamity we find an interesting adaptation. The egg at the end of the column hatches first, although it was necessarily the one laid last. The tiny caterpillar eats its way out of the sh.e.l.l and crawls over the other eggs to the leaf. Then the others hatch in succession.

The eggs thus deposited by the hibernating b.u.t.terflies are likely to be laid late in May or even early in June. They hatch into caterpillars less than a week later and these caterpillars feed for about a month, when they change to the characteristic chrysalids in which they commonly remain for a week or ten days. They then emerge as the summer brood of b.u.t.terflies, most of them in New England appearing during July. These remain upon the wing for several weeks, the females laying their eggs upon the elm and hop leaves. These in turn soon hatch into caterpillars that change to chrysalids in August and emerge as b.u.t.terflies late that month or during September. This autumn brood of b.u.t.terflies is quite abundant for a time but soon seeks the seclusion of winter quarters to remain until the following April.

There are thus two distinct broods during the year in the Northern states while as far south as West Virginia there are likely to be three broods.

These caterpillars at first simply eat small holes in the green substance of the leaf, but as they become larger each takes up its abode on the under surface of a single leaf and makes a sheltered tent in somewhat the same fashion that the Painted Lady does upon the nettle leaf. The caterpillar eats out more or less of the base of the blade on each side of the midrib, thus weakening the edges so that they can be fastened in a tent-like manner by silken threads. This serves as a resting place from which it sallies forth to feed, commonly only toward the tip of the leaf. As a result it often eats itself out of house and home and has to crawl to another leaf and construct a new shelter.

While the Comma is generally spoken of as a characteristic northern species it has a very wide range, being found from New England to Texas and from the Northwestern states to the Carolinas. It is one of those species which have two distinct forms of coloring. The winter form has been given the variety name _harrisii_. The b.u.t.terflies of this brood are decidedly lighter in color than those of the summer brood to which the variety name _dryas_ has been given. The latter was originally described as a distinct species by W. H. Edwards.

_The Change to the Chrysalis_

The manner in which a larva changes to a chrysalis is second in interest only to that in which a chrysalis changes to a b.u.t.terfly.

There are not a great many careful descriptions by competent observers of this process in print. One of the best of these is that by W. H.

Edwards in his splendid work on "The b.u.t.terflies of North America," in which he describes the transformation of the Comma caterpillar. It is as follows:

"When about to transform, the caterpillar selects a convenient place on the under side of a projecting rock, or of a fence rail, or of a weather board of the house, or the midrib of a hop leaf, and having spun a little b.u.t.ton of pale red silk fixes the hooks of its hind legs therein and hangs suspended, head downward, in the shape of a fishhook and remains immovable for the s.p.a.ce of twenty-four hours, no change being perceptible except in the color of the skin, which becomes partly transparent and loses its dark color owing to its gradual parting from the chrysalis within. Suddenly, and to a looker-on without any premonitory symptom, a rent takes place in the skin at the back of the head, just wide enough to allow the pa.s.sage of the chrysalis, the head of which at once emerges. By a rapid contraction and expansion of the folds of the abdomen the larva draws the skin upward, successively discovering the parts of the fully formed chrysalid until at last, and in scarcely more than one minute of time, the entire skin is gathered about the hind feet. It now bends itself violently to disengage the end of the chrysalis, which is long, pointed, and hard, furnished with several little hooks, meanwhile retaining its hold of the skin by the folds of its abdomen until after a severe effort, convulsively reaching out and feeling in all directions for the object of its search, it touches the b.u.t.ton of silk and at once grasps it with its hooks and fixes them in it securely.

Then by a twisting motion it manages to disengage the loose skin which falls to the ground and the chrysalis rests. The whole process is most interesting to witness and excites renewed wonder with every repet.i.tion at the ingenuity of the means employed and the delicacy of the instinct displayed. How to strip off the skin and much more the legs by which the creature is suspended without losing its hold, and at the same time to securely fasten the chrysalis, is a problem that would seem impossible to solve; and yet this little insect accomplishes it unerringly when to fail would be certain destruction.

And not this species only, but the larvae of all b.u.t.terflies which form suspended chrysalids, embracing the whole of the great family of Nymphalidae, that is, a large proportion of all the existing species of b.u.t.terflies, undergo a similar transformation.

"The chrysalis is now green in color, soft and indefensible, susceptible to the slightest injury, and for a few moments the several parts of the future b.u.t.terfly may be seen and readily separated; the wings folded close and enveloping the thorax, the antennae, and proboscis stretched at length along the back; but very speedily a complete casing is formed by the exuding from parts of the body of a viscous fluid, which binds together the tender parts and covers the whole with a coating like varnish. This soon hardens and the chrysalis is ready to take its chance against injury."

=The Gray Comma= _Polygonia progne_

This b.u.t.terfly is rather darker colored, especially on its under side, than the one last discussed. The silver marking takes on a little more definitely the form of an L than a comma, and the under surface of the wings is darkened by many blackish threadlike lines running across the veins. When at rest with wings closed these b.u.t.terflies are very easily overlooked.

Except for a difference in the food plants of the caterpillar, the life-history of the Gray Comma is very similar to that of the other Comma. The b.u.t.terflies hibernate, and in spring lay eggs singly on the leaves of currants, gooseberries, and related plants. The eggs soon hatch into caterpillars that feed upon these leaves but do not make any suggestion of a nest. They grow slowly and change into angular chrysalids which disclose the summer brood of b.u.t.terflies in July.

These lay eggs for another brood of caterpillars which mature into b.u.t.terflies in August and September. These generally go into hibernation before the middle of October, sometimes choosing simply the under side of a branch where their dark coloring, so near like that of the bark, is likely to cause them to be overlooked by their numerous enemies.

=The Green Comma= _Polygonia faunus_

The Angle-wings exhibit interesting variations in the geographical distribution of the species. Some are characteristic members of the Canadian fauna, others of the Alleghanian fauna. Some of those which are characteristic of the former are scattered south well into the latter, but the Green Comma is distinctively a northern species--being found abundantly in the great regions traversed by the trappers of the Hudson Bay Company and occurring south as far as northern New England, being very rare as far south as northern Ma.s.sachusetts. It is abundant on the higher slopes of the White Mountains.

As one might expect from the short seasons of the far northern regions in which this b.u.t.terfly lives, there is only one brood each year. In consequence the adult b.u.t.terflies live a long time. Coming from the chrysalis generally the first weeks in August, they remain upon the wing a month or more before they go into hibernation. They come from their winter quarters in May and commonly continue alive until late in June. Thus it is evident that many of these b.u.t.terflies must live at least ten months as adults, an extraordinary longevity for one of these frail creatures.

The caterpillars are known to feed upon the foliage of several kinds of plants. These include alder, currant, gooseberry, willow, and black birch, the last two named apparently being those most often chosen.

Mr. S. H. Scudder called attention to the fact that these b.u.t.terflies are able to make a slight clicking noise as they start into flight.

He described his experience in these words:

"Starting up a pair just at my feet on the Mt. Washington carriage road one day, I stopped abruptly to see whether they would settle again. After flying a few yards away to escape the cause of their disturbance, one turned back and dashed straight at my face, turning only when within three or four inches of my nose, and then suddenly whisked off with a distinct click as it did so, snapping its fingers, as it were, in my very face. There was no sort of doubt about this click, though if it had not been made so close at hand it would probably not have been heard. But other b.u.t.terflies in the tropics have long been known to emit sounds like this, which can be heard at a considerable distance; others, including some of our own b.u.t.terflies, are known to produce a rustling sound by the rubbing of one wing upon another; and movements of one sort and another have been so often observed, as of the opposite rubbing of the erect wings in most Lycaenids, and the tremulous agitation of the wings in many different sorts when excited, as to leave little doubt that sounds made by themselves and for the advantage of warning their brethren play a not unimportant part in the lives of b.u.t.terflies."

[Ill.u.s.tration: _See page 233_

MONARCH b.u.t.tERFLY IN RESTING POSITION]