Insect Architecture

by James Rennie

Nests of Polybia.

One very curious point about these cells is, that they are not uniform in their direction, as is generally the case with those of social hymenoptera. The greater part, such as the various wasps, hornets, and their kin, have the mouths of the cells downwards, while the cells of the hive-bee are nearly horizontal. But the cells of this insect are arranged without the least regard to their position, all the bases pointing towards the centre of the nest, and all the mouths radiating outwards.

Nests of Synæca and Polybia.

There seems to be scarcely any bound to the variety which exists in the nests of the social hymenoptera. The insect which makes the nest which is represented in the illustration is a native of Brazil, and is known to entomologists as Synæca cyanea. The first of these names is given to it on account of its social habits, and the second, in reference to the bluish colour of its body. It is rather larger than the preceding insects, being about three quarters of an inch in length. Its wings are brown.

The shape and size of the nest are exceedingly variable, but it is almost invariably longer than wide, and is fixed to a branch or some similar object. Sometimes it attains considerable dimensions, and has been known to measure a full yard in length. Yet, however large it may be, there is only a single comb, which is set upon the side of the nest next the branch, and, in consequence, has almost all its cells placed in a horizontal direction. In the illustration, the right-hand figure represents the external appearance of the nest, and the central figure shows the manner in which the single comb is set upon the branch. The nest which occupies the left hand of the illustration is made by a species of Polybia, and is here given in order to show a remarkable example of similarity in the mode of building adopted by two different insects. In the one case, however, the cells are all fastened by their bases to the branch, but in the other the cells are attached to one common base which is prolonged into a footstalk.

There have been lately discovered some very remarkable social nests. Specimens of both these nests may be seen in the entomological department of the museum at Oxford.

The first is formed very much like a rather flattened Florence flask, and is hung by the neck from the branch of a tree. It is made of a strong, parchment-like substance, formed by innumerable silken threads woven and matted together into a kind of felt. When it was cut open a most singular sight was exhibited. Nearly the whole of the interior was covered with the pupæ of some butterfly, all hanging by their tails, and many of them suspended to a twig which projected downwards into the nest. Although the nest is barely eight inches in length, a great proportion of which is taken up by the neck, about one hundred pupæ were found in it. At the bottom of the nest is a small and nearly circular aperture, through which the insects could make their way as soon as they escaped from the pupal envelope, and before their wings became extended and hardened.

The butterfly which makes this singular nest is a native of Mexico, and is named Eucheira socialis. The colour of its wings is dark brown, with an ill-defined white band across them.