Butterflies Worth Knowing Part 16

It has generally been supposed that this species is double-brooded in central and southern New England, the b.u.t.terflies of the first brood appearing early in July. These are said to deposit eggs which hatch into caterpillars that mature into b.u.t.terflies early in September.

These b.u.t.terflies live through the winter, laying eggs the following spring.

It is very probable that as far north as southern New Hamps.h.i.+re the species is commonly single-brooded. During one season when the caterpillars were unusually abundant, a very careful watch was kept for the second brood in New Hamps.h.i.+re and Vermont by several competent observers. Only one colony of caterpillars was found and this was at Durham in the southern part of New Hamps.h.i.+re near the seacoast.

Consequently, it seems safe to conclude that in northern and central New England, at least, a single brood is the rule rather than the exception. This involves the conclusion that the b.u.t.terflies seen upon the wing early in autumn are the same ones that developed in July, and that these same b.u.t.terflies remain alive through the winter and until, in the following May, they lay their eggs. Thus there is a period of ten months of existence in the b.u.t.terfly state, an extraordinary length of time for a b.u.t.terfly to live.

To a large extent the b.u.t.terflies disappear in August, and the question arises as to what becomes of them. Our observations lead to the conclusion that they go into summer quarters similar to those which they seek out for winter shelter. Apparently they fly about for a few days after coming from the chrysalis and then retire to cool woods, where under the side of a log or beneath the loose bark of a dead tree they settle down and to all appearances go to sleep. The instinct to remain quiet is very strong in these b.u.t.terflies. In taking the accompanying photographs, I found that even shortly after coming from the chrysalis the b.u.t.terflies when disturbed would fold their wings with the antennae between them, and drawing the legs against the body would lie quietly on their sides for a long time.

These same b.u.t.terflies would also hang downward from a limb by the hour in the hibernating position as shown in plate opposite page 32.

In the cooler weather of early autumn, the b.u.t.terflies come from their retreats and fly about in the suns.h.i.+ne. They are especially likely to be seen along the borders of woods or in open glades. At this time they love the suns.h.i.+ne, and will settle in a sunny place to bask in it.

_Going into Winter Quarters_

When the warm days no longer tempt them abroad, the Mourning-cloaks seek shelter in many sorts of situations--under loose bark, in hollow trees, under culverts and bridges, in woodpiles, in crevices of rocks, or alongside logs lying on the ground. In such retreats they remain until the suns.h.i.+ne of spring again calls them forth.

Prof. G. H. Parker's observations indicate that these b.u.t.terflies are very sensitive to changes of temperature, and he has seen the interesting action of the b.u.t.terflies crawling into their hiding places, finding that this takes place each day after they had been sunning themselves. Thus he writes:

"These b.u.t.terflies remain during cool spring nights in places similar to those in which they hibernate in winter, _viz._, in openings in stone walls, in old out-houses, in openings under the bark of trees, etc. They retire to these places with considerable regularity, so that in the open woods, where dozens of individuals may have been seen flitting about, all may have disappeared a quarter of an hour later. I have watched their retreat with some care. On a clear afternoon in early April I took my stand in a woodland where many Mourning-cloak b.u.t.terflies were on the wing. They continued actively flying about till approximately four o'clock, when I began to notice a diminution in their numbers. By a quarter past four not a b.u.t.terfly was to be seen. During the fifteen minutes from four o'clock on I followed two to their hiding places. One alighted on the front of a fallen tree and without expanding its wings crept immediately into a large crack in the bark. The second settled on a stone fence and crept into a hole between some loose stones. The period during which this occurred was marked not so much by a diminution of light as by a rapid fall of temperature."

That the habit of lethargy in cold and of resting upon the bark of trees is practically universal with this species is shown by a statement quoted by H. G. Adams in his book, "Beautiful b.u.t.terflies,"

published in England in 1871. The writer quoted says: "In a wood on the summit of the Drachenfels, when the wind was rather keen, I found numbers resting on the backs of fallen trees in a state of stupor.

They made no attempts to escape and when thrown into the air their wings barely opened or flapping feebly eased their fall or enabled them to seek repose on the stem of a rotten trunk."

_Its Rarity in England_

In many books this species is spoken of by its English name Camberwell Beauty. It is so called because it was first observed in the neighborhood of Camberwell in the county of Surrey, England. It seems that in that country it is a very rare species. This is a bit curious considering the fact that in America it is so extremely abundant. In his attractive little book quoted above, Mr. Adams begins the discussion of this species with this statement: "This is the crowning glory of the British b.u.t.terfly collector's cabinet, and a happy man is he who gets a perfect specimen of an insect which is at once so rare and so beautiful." And later in the same discussion is this further statement concerning the scarcity of the species: "In neither the larva nor the pupa state has the insect been found, we believe, in this country where its appearance occurs, except just here and there a single specimen or two, at long and uncertain intervals. About eighty years ago it was seen in many parts of the kingdom and again in 1819, but not since then although almost every year one or more specimens are taken or seen."

A curious fact in regard to the Mourning-cloak, as found in England, is that the border around the wings seems to be much more generally white than it is with us. J. O. Westwood in his book on British b.u.t.terflies describes the margin as of a white or whitish color and other writers speak of the same fact. Kirby in his "b.u.t.terflies and Moths" makes this comparative statement: "The border is whitest in British specimens, and perhaps yellowest in American ones." He speaks of it also as one of the rarest British species. It is sometimes called by the common name the White Border and also occasionally the Grand Surprise, appellations which bear out what has been said above both in regard to the color of the border and the rarity of the insect.

[Ill.u.s.tration: THREE MORE ANGLE-WINGS

Upper surfaces at left; under surfaces at right, slightly reduced

The Buckeye (_see page 188_) The Painted Beauty (_see page 163_) The Cosmopolitan (_see page 166_)]

[Ill.u.s.tration: _From a drawing by W. I. Beecroft_ _See pages 112, 171_

THE MOURNING-CLOAK Caterpillar, chrysalis, and b.u.t.terfly]

The Mourning-cloaks subsist upon a considerable variety of liquid food which they suck through their long tongues. In spring, when they first come from their winter quarters, they visit the stumps of recently cut trees and suck the exuding sap, a habit which they continue whenever opportunity offers. Mr. W. F. Fiske has noticed that they commonly sip the sap of maple twigs where the squirrels have gnawed the bark. A little later they visit the willow catkins to suck the nectar secreted by these blossoms, and still later they hover about the delicate blossoms of the mayflower, or trailing arbutus, for a similar purpose.

Probably many other flowers are thus rifled of their sweets, although this b.u.t.terfly seems to be a less regular visitor to flowers than are many of its allies. A little later, when the aphids, or plant-lice, have become sufficiently abundant so that the so-called "honey dew" is to be found upon the infested shrubs, these Mourning-cloaks sometimes sip the liquid sweet from the surface of the leaves. In April and May they occasionally visit the flowers of moosewood, and later in the season have been observed upon the blossoms of the common milkweed.

From the time the early apples ripen these b.u.t.terflies may often be seen beneath the orchard trees, sipping the liquids of the fallen and decaying fruit.

_The Parasites of the Eggs_

One fine spring morning I came upon a Mourning-cloak depositing a cl.u.s.ter of eggs upon a willow twig. She was so busily engaged that I was able to draw near and watch the operation for some time before she flew away. As soon as she was gone I was much interested to see a tiny parasitic fly running eagerly over the newly laid eggs, and this fly also was so busily interested in her work that I was able to cut the twig off and sit down to observe at leisure through a lens the actions of the insect. I dictated to a companion my notes of these observations and so was able to get rather a complete record of the process of oviposition.

The tiny fly would stop over one of the b.u.t.terfly eggs, holding its body vertical with the hind legs far back and the other legs so straightened out as to hold the front of the body high up. Then it would insert its tiny ovipositor through the egg sh.e.l.l and proceed to deposit an egg of its own inside of the larger egg of the b.u.t.terfly.

At least it seemed a safe a.s.sumption that this was what happened although of course it was impossible to see the smaller egg at the time. While thus engaged the antennae of the tiny fly were bent directly downward to the egg beneath. In about a minute the fly withdrew its ovipositor and after running around for a few seconds again settled upon another egg and repeated the operation. Then it tried again on a third egg, after which I got out my watch and began timing the process. These are the results in the case of the next dozen eggs that were laid. It required:

94 sec. to lay egg No. 4. Then fly moved around 26 sec.

120 " " " " " 5. " " " " 27 "

83 " " " " " 6. " " " " 20 "

92 " " " " " 7. " " " " 22 "

75 " " " " " 8. " " " " 40 "

90 " " " " " 9. " " " " 42 "

102 " " " " " 10. " " " " 15 "

120 " " " " " 11. " " " " 21 "

120 " " " " " 12. " " " " 18 "

60 " " " " " 13. " " " " 25 "

120 " " " " " 14. " " " " 25 "

60 " " " " " 15. " " " " 50 "

It thus required an average of about two minutes per egg for the laying of these fifteen eggs. I then caught the little fly and sent her to Dr. L. O. Howard, our greatest authority on this group of insects, to learn the name of the parasite. He identified it as _Telenomus graptae_, a well-known parasite of the eggs of the Mourning-cloak and related b.u.t.terflies.

The most interesting thing about this observation was the fact that the little fly had apparently begun its operation before the mother b.u.t.terfly had finished laying her cl.u.s.ter of eggs. There were thousands of willow twigs in the immediate vicinity. How did this tiny creature arrive at this particular place at the particular moment when from its own point of view it was most needed? Had it been riding around upon the body of the b.u.t.terfly waiting for the time when she should lay the eggs? Or was it attracted to them from somewhere in the immediate vicinity? That this early arrival probably takes place generally is indicated by the fact that a similar observation had been made in the White Mountains by Prof. C. W. Woodworth.

The history of the egg parasite after the laying of the egg seems to be comparatively simple. It soon hatches into a tiny larva that develops within the sh.e.l.l at the expense of the contents. It finally changes to a pupa which in turn changes to the little fly that gnaws a hole through the egg sh.e.l.l and emerges to the outer world.

_The Parasites of the Caterpillars_

After hatching from the egg, the Mourning-cloak caterpillars are also subject to the attacks of various parasites. One of these is quite minute, not a great deal larger than the egg parasite. It is a tiny four-winged fly which deposits many eggs in a single caterpillar. The eggs hatch into tiny maggots that grow at the expense of the caterpillar, finally killing it and changing to four-winged flies again. As many as 145 of these parasites have been known to emerge from a single dead caterpillar. These little flies are called Chalcids by entomologists.

There is still another group of four-winged flies, some of which attack the Antiopa caterpillars. These are much larger than the Chalcid flies and are called Ichneumon flies. In the case of these, only one or two parasites develop in each caterpillar or chrysalis.

In addition to these various four-winged flies, there are certain two-winged flies, called Tachinid flies, that develop at the expense of the caterpillars. In New Hamps.h.i.+re, during recent years, these appear to have been the most abundant parasites of these insects. An egg is laid on the skin of the caterpillar by a two-winged fly, similar in general appearance to the figure below. The contents of this egg shortly develop into a tiny grub that burrows through the egg sh.e.l.l and the skin of the caterpillar into the inside of the body.

Here it remains, absorbing the body substance of its host and gradually increasing in size. In a few weeks it becomes fully developed in this grub state. By this time the caterpillar has become sluggish from the effects of the parasite. If the branch upon which it feeds is disturbed, the other caterpillars are likely to crawl away, but the enfeebled victim remains in its place.

[Ill.u.s.tration: Tachinid Parasite. (Slightly magnified.)]

Shortly after becoming full grown, the Tachinid grub breaks through the skin of the dying caterpillar and, falling to the ground, changes to a peculiar pupa; the outer skin of the grub turns brown and becomes hard, forming a protective covering for the body inside. A week or two later the insect undergoes another change and emerges as a two-winged Tachinid fly, like the one that laid the egg some weeks before.

_Other Enemies_

Besides those insects that develop on the inside of the bodies of these Antiopa caterpillars there are other insect enemies which attack them from the outside and devour them bodily. The most notable of these, perhaps, is a large beetle commonly called the Caterpillar Hunter; it is known to entomologists as _Calosoma scrutator_. This is a very active insect, with large strong jaws, that runs rapidly about in search of victims. In some cases it has been observed while destroying many of the Antiopa larvae.

In the Southern states a common reddish wasp--a species of Polistes--has also been observed attacking these caterpillars, and there are probably various other insects that destroy them, although definite observations showing this have not been recorded.

The Antiopa caterpillars are such spiny creatures that comparatively few birds attack them. They are devoured, however, by the two species of cuckoos--the yellow-billed and black-billed--and it is probable that they are sometimes killed by Baltimore orioles and various other birds. They are also greedily devoured by toads, but of course they do not often come within the reach of these useful animals.

Even the adult b.u.t.terflies of this species have to be on the lookout for enemies. During the long months of their life many of them probably succ.u.mb to the attacks of birds or other creatures. I have seen but one such tragedy. While riding along a country highway with a bird-loving friend one spring day we saw a male Maryland yellow-throat flit by with a Mourning-cloak in his mouth. The bird lit on a fence, from which I startled him so that he dropped the b.u.t.terfly, a worn and faded, half-dead specimen. The places where the bird held the insect were indicated by missing pieces of the wings.

=The American Tortoise-sh.e.l.l= _Aglais milberti_