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

Our last example of the pensile nests formed by the hymenoptera is a truly remarkable one. For some time I could scarcely decide upon its place in the present work, whether it was to be ranked as an example of the pensiles, social insects, or builders. On account, however, of the locality which is chosen for it, and the peculiar method by which it is attached to the branch, I have decided upon placing it among the pensile nests.

It has already been mentioned that the members of the genus Polistes are in the habit of building their cells in the open air, and leaving them without covering to defend them.

The shape, material, and arrangement of the comb is extremely variable; some, as that which has already been mentioned, hanging their cell-masses to the branches, just as if a number of bee-combs were simply hitched on the twig by the simple process of boring a hole in the upper part of the comb, and pushing the twig through it; others, again, making their cells of mud, in a nearly globular shape, and fastening them on the branches like so many berries. The species, however, which makes the cells represented in the illustration is one of the most remarkable, and so elegant is the form of the combs, and so singular the method of their attachment, that I have had them drawn nearly of the natural size.

Generally, the shape of the comb is nearly round, as is seen in the upper figure of the illustration. The cells are remarkable for their radiating form, the bases being a trifle smaller than the mouths, a peculiarity which would hardly be noticed in a single cell, but which produces the spreading outline when a number of them are massed together.

Nests of Polistes.

<!-- pandi-media-anchor:figure-p303-o51-7bd385f6f21176dd -->

Some of the cells, those in the middle for example, are much longer than the others, and in the specimens in the British Museum many of them are closed at the mouth, showing that the insect is within, and has not yet attained its perfect state. Those on the circumference, however, are much shorter, and are entirely empty, not having been yet occupied. It is very possible that these cells would have been lengthened had the insects been left to themselves.

Although the circular shape is mostly the rule with these combs, so that they look something like withered dahlias or chrysanthemums, it is not the invariable form. If the reader will look at the lower figure in the illustration, he will see that it is much wider than long, and is apparently composed of two of the circular combs fixed together.

Now comes the curious part of the structure. The combs are not fastened directly to the branches, but are attached to footstalks which spring from their centre, and are firmly cemented upon the branch or twig. How wonderfully the insect must manage the comb so that it shall be balanced on this slender footstalk! To preserve the equilibrium of even an empty comb would be difficult enough, but when the cells are filled with fat, heavy grubs, the difficulty must be multiplied with every one.

The footstalks are made of the same papier-maché-like substance as the cells, only the layers are so tightly compressed together that they form a hard, solid mass, very much like the little pillars which support the different stories of an ordinary wasp's nest, but of much greater size. The position of the combs is extremely variable, some being nearly horizontal, and others perpendicular, as shown in the illustration. These nests came from Bareilly, in the East Indies.

HAVING now completed our notice of the pensile hymenoptera, we turn to another order of insects.

We can hardly expect to find that any of the beetles can be ranked among the pensile insects, their appearance and general habits being opposed to such an idea. The variety of nests made by the hymenoptera leads us at once to conjecture that some of them may be pensile, for it is at least likely that the little architects which can construct the marvelous system of the honeycomb, or the complicated galleries of the ant's nest, or contrive the wonderful homes of the leaf-cutter bees, would be also able to make nests which could be suspended from leaves or branches. But there is nothing in the general history of beetles which could lead us to place them among the pensile insects, a rank, however, which can be taken by a very few species, most of which belong to a single group.

This group is that of the Curculionidæ, or Weevils, and there are a few species of these long-snouted beetles which make for themselves certain pensile habitations of a most elegant form. Two genera of Weevils are remarkable for the beauty of their cocoons, namely, the Hypera and Cionus.

If the reader should desire to possess specimens of these cocoons, he can not do better than procure some seeds of the common species of Verbascum, say the Great and White Mulleins (Verbascum Thapsus and Lychnitis), and sow them in sandy or gravelly soil. The beetles of the genus Cionus feed on the mulleins, and when they are about to change into the pupal state, do not trouble themselves to leave the plant upon which they have been feeding. So fond are these beetles of the Verbascum, that Mr. Stephens found on a solitary plant, which was growing in a garden at Ripley, all the five species of the genus.

During the month of August the larvæ may be found in the flowers and seeds, and one species burrows into the leaves themselves, getting between the two membranes, and feeding on the soft green parenchyma. When the larvæ are about to enter the pupal state, they cease from feeding, and spin for themselves cocoons of a most remarkable shape. The cocoons are very small, being on the average about as large as sweet peas, and nearly as globular. They are constructed of a rather stiff and glutinous thread, which is so wonderfully twined as to form large open meshes of a nearly circular form.

The cocoon is very firm and elastic, feeling and looking very much like those hollow spheres and cylinders that artists in hair are so fond of making. The open meshes are so large that the inclosed pupa can be seen through them, so that there is but little protection from the elements. A very good idea of the general appearance of the cocoon may be obtained from the toys which are made from nuts by neat-handed school-boys, by the simple process of boring them full of holes until the shell is reduced to a kind of wooden network with circular meshes.

All the beetles of the genus Cionus are pretty little creatures, very hard shelled, nearly as globular in form as the cocoon, and marked with dark patches and streaks.

The cocoons of the genus Hypera are also made with open meshes, and of a similarly stiff thread, but the form is oval instead of round. The larva of the Hypera is long and narrow, having its rings or segments very deeply cut, covered with bristle-like hairs, and having some light lines along the back and sides.

The "Charançon de la Patience" of De Geer is a beetle of this genus. In both cases the cocoons are affixed to the under side of the leaves, whether they are attached to the mullein or the heath, so that they are not readily seen except by careful observers, who know where to look for them. In the insect room at the British Museum there is a beautiful series of these delicately formed cocoons still adhering to the dry and shriveled leaves of the plant on which the beetle had fed.

WE now come to the pensile lepidoptera, of which a number of specimens will be mentioned. They all belong to the moths, the pensile butterflies being content with suspending themselves by a couple of threads, without taking the trouble to build or spin a nest.

One of the most beautiful of these nests is the cocoon of the common EMPEROR MOTH (Saturnia pavonia-minor). The moth itself is very beautiful, with its broad, soft-plumaged, pink-eyed wings; but it is even equaled by the larva in beauty of color, a phenomenon not very usual among the lepidoptera. The rings or segments of the caterpillar are rounded and deeply cut, and are remarkable for the tufts of golden-colored bristles with which they are covered, each tuft springing from a raised and rounded tubercle. The body itself is of a beautiful leaf-green.

The cocoon which is made by this remarkable insect is extremely beautiful, though its beauty does not appear to a careless observer. Some twenty years ago, when I first began to study practical entomology, and had no access to the books that were then published on the subject, I took to breeding every caterpillar that could be found, not having the least idea what kind of being would issue from it. Among them was a caterpillar which struck my fancy so much, by its green body and golden tufts, that I made a colored drawing of it, and constructed for its benefit a separate cage, wherein it lived for some little time, and then spun a silken cocoon of a flask-like shape, very rough and loose on the exterior.

Some time afterward, upon looking into the box, I saw a beautiful moth clinging to the side. How the creature had gained admission I could not conceive, for the cocoon seemed to be perfectly intact, and to exhibit no signs that an insect had broken through the walls. Concluding, however, that the moth might have crept into the box without my knowledge, or might have been placed there by some kind friend, I set it, and watched the cocoon as usual. After a whole year had passed, I thought that there must be something wrong, and so took out the cocoon and carefully cut it open.

The mystery was at once explained. Within were the cast shell of the chrysalis, and the dried, shriveled skin of the caterpillar, crushed up into a very small space, but recognizable by the hairy tufts. The manner in which the moth had escaped was also evident. Taking as our model a common Florence oil-flask, from which three fourths of the neck have been removed, we shall obtain a clear notion of the method by which the cocoon is made, so as to allow the egress of the moth, and at the same time to show no aperture through which the creature had emerged.

Let us suppose the material to be stiff, bristle-like hair, and that the body of the flask is made stiff and firm by cementing the hairs together, while they project loosely at the neck. Now let us farther suppose that these projecting hairs are all bent inward, so as to cross each other slightly, and we shall have a tolerably correct idea of the manner in which the cocoon of the Emperor Moth is made. It will be seen that, if a creature try to push its way out from the inside, the hairs will yield and allow it to pass, but that if any insect tries to push its way in from the outside, the converging hairs are pressed tighter together, and effectually debar it from gaining admission.

This beautiful structure is not visible until the observer strips away a thick, loose coating of yellow-white silk which covers the cocoon, and probably acts as a non-conductor of heat as well as a protection from the weather. This cocoon may be found upon the plant on which the insect feeds, but the best method of procuring perfect specimens is by searching for the caterpillars and feeding them until they change.