Homes Without Hands: Being a Description of the Habitations of Animals, Classed According to Their Principle of Construction - Page 91

These Grakles exist in great numbers, and sweep over the land in vast flocks, like our own starlings, their wings sounding like the blast of a tempest as they rise from the ground, and their bodies darkening the air. "A few miles from the banks of the Roanoke, on the 20th of January, I met with one of these prodigious armies of Grakles. They rose from the surrounding fields with a noise like thunder, and, descending on the length of road before me, covered it and all the fences completely with black; and when they again rose, and, after a few evolutions, descended on the skirts of the high timbered woods, they produced a most singular and striking effect, the whole trees, for a considerable extent, seeming as if hung in mourning; their notes and screaming the mean while resembling the distant sound of a great cataract, but in more musical cadence, swelling and dying away on the ear according to the fluctuations of the breeze."

It is evident that such vast multitudes of birds can not all have been nurtured in the interstices of osprey nests. Indeed, the generality of the birds build in tall trees, usually associating together, so that fifteen or twenty nests are made in the same tree. The nests are well and carefully made of mud, roots, and grasses, about four inches in depth, and warmly lined with horsehair and very fine grasses. The fact that the bird possesses this capability of nest-building gives more interest to the occasional habit of sharing its home with the osprey: a privilege of which it seems to avail itself whenever an osprey's nest is within reach.

The color of this bird appears at a little distance to be black, but is, in reality, a very deep purple, changing in different lights to green, violet, and copper, and having a glossy sheen like that of satin.

Our little friend the SPARROW (Passer domesticus) is occasionally a parasite, following to some extent the custom of the purple grakle, though it does not select a bird of prey for its companion.

On the Continent, the common Stork builds largely, and in several countries is protected by general consent, the slaughter of a stork, or the destruction of its nest and eggs, being visited with a heavy fine. In consequence of this immunity, the Stork is very tame, building upon houses as freely as does the martin, and being considered as a bringer of good luck when it does so.

Any disused chimney is sure to have a stork's nest upon the top, and so is a pillar, or any ruin. The nest of the stork bears a general resemblance to that of the osprey, and, with the exception of the sea-weed, is made of similar materials. It is of huge dimensions, and chiefly consists of sticks and reeds, heaped together without much arrangement, and having on the top a slight depression, in which the eggs are laid. As in the case with the osprey nest, considerable interstices are left between the sticks, and in these spots the Sparrow loves to place its nest. Mr. F. Keyl has told me that he has repeatedly seen the Storks and Sparrows thus living in amity together, the stork appearing to extend to a weaker bird that protection which it receives from mankind.

WE now pass to the Parasitic Insects. As this work is intended to describe dwellings which are in some way formed by the creatures, it is necessary to exclude all the parasite insects that may exist upon the animal, and make no habitation, such as the ticks, as well as those which are merely parasitic within the animal, such as the various entozoa.

Of Parasitic Insects, the greater number belong to that group of hymenoptera which is called Ichneumonidæ, and which embraces a number of species equal to all the other groups of the same order. Being desirous of producing, as far as possible, those examples of insects which have not been figured, I have selected for illustration several specimens which are now in the British Museum, one or two of which have only been recently placed in that collection.

THE best known of all the Ichneumonidæ is that tiny creature called Microgaster glomeratus, of which a casual mention has already been made in page 289.

A group of these insects and their cells is now before me, and will be briefly described.

The insects themselves much resemble in general form the Burnet Ichneumon, which is mentioned on pp. 290, 292, but are smaller, blacker, and not nearly so beautiful, although their wings gleam with an iridescence nearly as brilliant. Small as it is, this tiny insect is extremely valuable to us, and to the gardener is beyond all value, though, as a general rule, the gardener knows nothing about it. Were it not for this ichneumon, we should scarcely have a cabbage or a cauliflower in the garden; for the noisome cabbage caterpillars would destroy every leaf of the present plant, and nip the growth of every bud which gave promise for the future.

Every one knows the peculiarly offensive caterpillars which eat the cabbages, and which are the offspring of the common large white butterfly. In the spring the butterflies may be seen flitting about the gardens, settling on the cabbages for a few moments, and then flying off again. They look very pretty, harmless creatures, but, in fact, they are doing all the harm that lies in their power. Forty or fifty eggs are thus laid on a plant, and if only one quarter of the number are hatched, they are quite capable of eating every leaf. In process of time they burst from the egg-shell and commence their business of eating, which is carried on without cessation throughout the whole time of the larval existence, with a few short intervals, while they change their skins.

Parasitic Insects.

Cocoon of Oak-egger Moth (Cryptus fumipennis). Cocoon of Puss Moth (Paniscus glaucopterus).

Cocoon from New South Wales (Pimpla). Cocoon of Goat Moth (Lamprosa setosa).

When they are full grown they crawl away from the plant to some retired spot, and there suspend themselves, preparatory to changing into the pupal condition. A few of them succeed in this task, but the greater number never achieve the feat, having been the unwilling nourishers of the ichneumon flies. Just before the larva is about to pass into the pupal state, a number of whitish grubs burst from its sides, and each immediately sets to work at spinning a little yellow oval cocoon. The walls of the cocoon are hard and smooth, especially in the interior; but the outside is covered with loose floss-silk, which serves to bind all the cocoons together. Generally they are very loosely connected; but a group of these little objects is now before me, where the cocoons are formed into a flattish oval mass, about the size and shape of a scarlet-runner bean, split longitudinally, and are bound so tightly together that their shape can barely be distinguished through the enveloping threads.

As is the case with the cells of the Burnet ichneumon, each cell is furnished with a little circular door, which exactly resembles in shape and dimensions the circular pieces of paper that are punched out of the edges of postage-stamps. On the average, about sixty or seventy ichneumon flies are produced from a single cabbage caterpillar.

The groups of yellow cells are very plentiful toward the middle of summer and the beginning of autumn, and may be found on walls, palings, the trunks of trees, in outhouses, and, in fact, in every place which affords shelter to the caterpillar. Nothing is easier than to procure the insects from the cocoons, as the yellow mass needs only to be put into a box, with a piece of gauze tied over it by way of a cover. Nearly every cocoon will produce its ichneumon, and as the little creatures are not strong-jawed enough to bite through the gauze, they can all be secured.

There are many species of Microgaster; but those which have been mentioned are the most important, and make the most interesting habitations.

THE large oval cocoon was brought from New South Wales, and is evidently the produce of some lepidopterous insect, probably a moth allied to the silkworm. Upon the larva which constructed the cocoon an ichneumon has laid her eggs, and the consequence has been that the caterpillar has been unable to change into the pupal condition, but has succumbed to the parasites which infested it. These insects are not of minute dimensions, like the Microgaster, but are tolerably large, and, in consequence, can be but few in number. The cells are very irregular in shape, and are not rounded like those of many Ichneumonidæ, but have angular edges.

In this, and in one or two other examples which are shown in the illustration, the reader will note a peculiarity in the development of the parasite. The Microgaster larvæ emerge from the caterpillar just before it undergoes its change into the pupal condition, and effectually prevent that change by killing the creature in which they had been nurtured. But, in many instances, the ichneumon larva delays its escape until the caterpillar has completed its cocoon, and in some cases waits until the change into the pupal state has been achieved. In the present example, the larva has permitted the cocoon to be made, and then killed the caterpillar, the reason of this delay being that the cocoon is very firm and strong, and affords an impregnable shelter to the parasite. The names of the Parasites are placed beneath the cocoons.

WITHIN the same case there are several cocoons in which a similar calamity has befallen the caterpillars which made them. There is, for example, a cocoon of the OAK-EGGER MOTH (Lasiocampa quercus), the interior of which resembles that of the insect which has just been described, except that the cells of the parasite are more numerous. This species of caterpillar is peculiarly subject to the attacks of the ichneumon flies, as is well known to all practical entomologists, who lose many of their carefully-bred specimens by means of these insects.

There is also one of the winter cocoons of the Goat MOTH caterpillar, the inmate of which has been pierced by the ichneumon fly, and killed by its young. As the species of ichneumon is a large one, only a single individual was produced, and, as may be seen from the cell of the parasite which is placed by the side of its victim, the habitation of the ichneumon is so large that it must have occupied nearly the entire cocoon of the dead caterpillar.

In another room, placed among the series of British moths, is a cocoon of a Puss MOTH (Cerura vinula) which has been occupied by two ichneumon larvæ.

If the reader should happen to know the cocoon of this moth, he will remember that it is made of wood scrapings, glued together with a cement secreted by the insect, and that its walls are so hard that a tolerably strong knife is required in order to cut it open. That the eggs of a parasite should be introduced into the body of the larva is not an extraordinary circumstance, but that the perfect insects should be able to make their way out of such a cocoon is really wonderful. The interior of this cell is hard and smooth as if made of polished ebony, and its concavity renders it more difficult of penetration. Yet these singular insects contrive to make their way through the sturdy walls.

The ichneumons which usually attack the Puss Moth are rather large insects, belonging to the genus Ophion, and have long, slender, curved abdomens, and long antennæ slightly twisted at the ends. The color is orange, diversified with black. Those which have made their cells in the above-mentioned cocoon belong to the species called Paniscus glaucopterus, and are of a yellowish hue. It sometimes happens that the insects fail in making their way through the cell walls and die in the interior. This accident, however, seems chiefly to befall the ichneumons produced in cocoons which are kept in houses for the purpose of breeding the Puss Moth, and which are, in consequence, harder and more dry than those which remain in the open air, adhering to the trunks of trees.

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