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

The last point which will be noticed in connection with this remarkable cell group is that it is perfectly protected from rain. Slight and delicate as is the structure, appearing scarcely thicker than the silver paper with which engravings are guarded, it may be deluged with water without being wetted. Over the whole of the cells the insect contrives to lay a thick coat of some varnish-like substance, which at the same time gives the exterior of the cells a polish, binds them more firmly together, and renders them water-proof. The varnish is nearly transparent, but has a blackish hue, which gives to the whole cell group a uniformity of aspect which would be wanting if the protecting substance were itself colorless.

The insect is, at first sight, black in color, as is expressed by its specific title. A clear examination in a more favorable light shows that the true color is a green so deep as to appear black, but having a perceptible bronze gloss in certain lights. The wings are equally sombre in aspect, looking as if they had been held above the flame of a badly-trimmed lamp, and received all the soot upon their translucent membranes. Indeed, their peculiar color can only be expressed by the word "smoky."

IT is hardly possible to overrate the wonderful varieties of form that are assumed by the nests of insects—varieties so bold and so startling that few would believe in the possibility of their existence without ocular demonstration. No rule seems to be observed in them; at all events, no rule has as yet been discovered by which their formation is guided, neither has any conjecture been formed as to the reason for the remarkable forms which they assume.

Perhaps, of all the nests in the splendid collection of the British Museum, there are none that cause so much surprise as the wonderful group which is represented in this illustration. Many

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persons pass through the room, and even take some notice of the various nests with which they are surrounded, but they seldom notice the peculiarities of this group until pointed out to them. When, however, their attention is directed toward it, they never fail to express their surprise at so curious a structure, and their admiration of the manner in which these natural homes are constructed.

In a recent portion of this work the hexagonal principle of construction has been mentioned as applied to separate cells of certain hymenoptera, and that no explanation has been given of the mode by which the six-sided cells are made. It is always easier to explode previous theories than to supplant them with one that really explains the enigma, and such is certainly the case with these cells. But when we come to examine the group of nests which are made by an insect called Apoica pallida, the subject takes a wider range, and we are even more hopelessly bewildered than before. In the nests already mentioned the cells are hexagonal, but in these specimens the entire nests assume a form more or less hexagonal, as may be seen by reference to the illustration.

In order to prevent misunderstanding, I must here remark, that the seven nests or cell groups were not all found adhering to a single branch, as seems to be the case, but that they have been placed near each other in such a manner as to allow of easy comparison, and to show their peculiar form. The large mushroom-shaped nest in the centre, and the small cell group which occupies the extremity of the bough, appear as they were formed by the insects, but the others have only been arranged for the convenience of comparison.

Even their position has been necessarily altered. Nests of this kind are always placed with the mouths of the cells downward; but, as their peculiar form could not easily be seen if they were allowed to retain their natural position, some of them have been set on their edges, so as to exhibit their outline to the spectator. This is notably the case with that nest which occupies the left hand of the illustration, and which is the most hexagonal of all the specimens.

If the reader will refer to the illustration, he will see that the nests are by no means uniform in size or shape. The larger one, for example, which occupies the centre, rather exceeds ten inches in diameter, while the small nest at the end of the same branch is scarcely half as wide, and the others are of all the intermediate sizes. In shape, too, they differ, some being perfectly hexagonal, others partly so, while others, again, are nearly circular, though on a careful inspection they show faint traces of the hexagonal form.

We will now examine these nests, and see where they agree with and differ from each other.

In the first place, their upper surfaces are more or less convex, according to their size; and whether they are circular or hexagonal, the convexity remains the same. This form is evidently intended for the purpose of making them weather-proof, for the rain torrents that occasionally deluge the country would soon wash to pieces any nest whereon the falling drops could make a lodgment. The surface is therefore as smooth as that of the various pasteboard wasps which build in the forests of tropical America.

The upper surface being convex, it naturally follows that the under surface is concave, inasmuch as the cells are of tolerably equal length. In fact, the nests somewhat resemble very shallow basins with very thick sides, and bear an almost startling resemblance to the cap of a very large and very well-shaped mushroom, the central specimen being so fungus-like in form that, if it were laid on the ground in a waste and moist spot, it would soon be picked up as a veritable mushroom. The color, too, is yellowish-brown, and the surface has a kind of semi-polish that increases the resemblance.

In the nests of our common wasp, or hornet, the sheets of paper which form the exterior show plainly where each successive flake has been deposited, and the sweep of the insect's jaws is marked distinctly upon the yielding material. Even in the case of the few British species which build pensile nests in the open air, the separate flakes can be distinguished, though they are not so clearly marked as in those homes which are defended from the weather by earth or wood. Our temperate region knows no such sudden vicissitudes of weather as take place near the equator, and there is no need for insect habitations to possess very great strength or powers of resisting water. But in these nests the cover is so beautifully uniform, that no trace of a jaw can be detected upon it.

Agreeing in general appearance, the nests vary somewhat in color. Of the eight specimens, the generality are of the mushroom-like hue which has already been mentioned. Others, however, rather vary in this respect, and the uniform yellowish-brown is pleasingly diversified by patches of red. One of the nests, however, boldly departs from the general uniformity, the surface being not only reddish-brown over its whole extent, but as rough as if made of sand-paper, or from the skin of a dogfish. One or two, again, are much darker than the others; while one is almost white, with only a tinge of gray.

Another point in these nests is, that although they vary so much in diameter, their thickness is almost uniform. The reason is evident enough. As the young larvæ attain a tolerably uniform size, and are not boldly divided into large males, larger queens, and little workers or neuters, the cells are of equal length. Therefore, whether the number be great or small, the thickness of the cell group remains unchanged, though the diameter may increase to any reasonable amount.

All the nests are fixed in the same manner, a branch or twig passing through the upper surface. When the nest increases in size, the original support is often found to be too slight, and in that case others are added. The smaller nests are upheld by a single twig only, but the largest is supported at no less than three points, two tolerably stout branches passing through the side of the cover, and a smaller twig supporting the top.

Another point to be noticed is, that the size of the nest is no criterion of its shape. It is not necessarily circular because it is large, nor hexagonal because it is small. The eight examples in the British Museum show every gradation of shape between the hexagon and the circle, without the least reference to size.

How the insect forms these wonderful cell groups is an enigma to which not the least clew can be found. In proportion to the size of the architect, they are simply enormous, and yet the sides and angles are as true and just as if they were single cells. It is very clear that neither the theory of excavation or of equal pressure can apply to these nests, and an additional reason is afforded why these theories should be abandoned. It is to be regretted that the only reasoning is of the destructive kind; but at present we have no data on which to found a theory that seems in the least tenable.

In the nest to which reference has been made, the insects have carried out the hexagonal principle in a curious manner. A number of cells whose mouths are closed with a white silken cover prove that the inmates are undergoing their metamorphosis, and are in a transitional state between the larva and the perfect insect. Instead, however, of being scattered at random throughout the nest, the inhabited cells are arranged in the most systematic manner, a group occupying the centre, and being surrounded at a little distance with a row of covered cells which follow the shape of the exterior outline, and therefore take the shape of a hexagon.

The insect well deserves its scientific title. The generic name Apoica is formed from two Greek words, which signify a colony, and the specific title pallida is given in reference to the hue of the body. It is not a handsome nor even a striking insect, being long, slender, and very pale yellow, looking as if it had once been decorated with a brighter covering. It has altogether a faded and semi-bleached look, suggesting to a practical entomologist that it had been subjected to sulphur-fumes, and thereby lost its coloring. Even the wings have the same pallid hue as the body, but with a white cast, and altogether the insect seems far too purposeless of aspect to construct houses which demand so much energy as those which we have just examined.

THE last example of insect pensile nests is, I believe, one that has not yet been described, owing to its recent arrival in this country.

While I was examining some specimens in the insect-room of the British Museum, two gentlemen brought for examination a box full of insect habitations which they could not identify with those of any known species. At first sight they appeared to be specimens of galls, but a more careful inspection soon showed their real character. They were formed very much like those of the House-builder Moth (see page 302), but with a singular addition. Several specimens are now before me, which will be briefly described.

The foundation of the nest is a structure of leaf-stems and fragments of leaves, varying much in size, some being thicker than crow-quills, and others as fine as ordinary needles. These are arranged crosswise upon each other, so that the nest might easily be mistaken for that of a large caddis-worm. The nests, however, differ much in form, size, and material, some being half as large again as others, and some being made almost entirely of large pieces of leaf, and others chiefly of stems, among which the leaf-fragments are closely pressed.