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

To procure the insects of this and many other galls is no very difficult task. The branch to which they adhere should be cut off, and placed in a bottle of water, and a piece of very fine gauze tied net-wise over it. The insects, although they can eat their way out of the gall in which they have been bred, never seem to think of subjecting the gauze to the same process, and therefore can be always secured. It is needful, however, to procure galls which are tolerably near their full age, as a branch can only be kept alive for a limited time, and if the supply of nourishment be cut off by the death of the branch, the inclosed insect becomes stunted, if not deformed.

The galls produced by Cynips terminalis are those which are so greatly in request upon the twenty-ninth of May, and which, when covered with gold leaf, are the standards under which the country boys are in the habit of levying contributions. A figure of this gall is seen in the illustration.

SOME years ago, when I was calling at the office of the Field newspaper, then recently started in its race for popularity, I was shown some oak branches containing a vast number of hard, woody, spherical galls, and asked if I could tell the name of the insect which had produced them. They had recently made their appearance in the country, and no one knew any thing about them. A branch beset with these galls is shown in the right-hand upper corner of the illustration, the figures being necessarily much reduced.

I was totally unacquainted with them, but in the following year found many of them on Shooter's Hill, in Kent, where the growth of oaks is very dense. At the present day they have increased so rapidly that they outnumber almost every species, if we except the tiny spangle galls, and I have bred great quantities of the insect. The creature which made them is named Cynips Kollari, in honor of the celebrated entomologist, and is plentiful on the Continent. I believe that it has long been known in Devonshire, though in Kent it has only recently made its appearance.

The galls produced by this insect are wonderfully spherical, of a brown color; smooth on the exterior, and about as large as white-heart cherries. Each contains a single insect, which undergoes all its changes within the gall, and eats its way out when it has attained the perfect form. Occasionally two galls become fused together, and in my collection there is a very curious example of these twin galls. They form a figure like that of a rude hour-glass, and each portion has contained an insect. The inhabitant of one portion has eaten its way out and escaped, but the other has met with a singular fate. By some untoward error, it has taken a wrong direction, and instead of issuing into the world in the ordinary way, has hit upon the neck which connects the two galls, so that, instead of merely piercing half the diameter of the gall, it would have been forced to gnaw a passage equal to three half diameters.

Natural powers are always adjusted to the work which their possessors have to perform. The insect was gifted with the capability of eating her way through the walls of her own habitation, but not with the power of making a passage through another gall afterward. As a natural consequence, she has died from exhaustion before she could emerge into the air; and when I cut the double gall, in order to see how the inmates had fared, I found the dead insect lying near the middle of the second gall, so that she was even farther from the outer air than when she started on her course.

The Cynips Kollari is larger than the generality of the family, equaling a small house-fly in dimensions. Its color is pale brown. A figure of the insect may be seen in the illustration.

NEARLY in the centre of the illustration is seen a figure of the well-known gall that is so common on the rose, whether wild or cultivated, and which is popularly known by the name of BEDEGUAR. This gall is caused by a very tiny and very brilliantly-colored insect, named Cynips rosæ, which selects the tender twigs of roses, and deposits its eggs upon them.

I have now before me quite a collection of these galls, some of which are so variable in shape that they scarcely seem to have been made by the same species of insect. When the Cynips rosæ deposits her eggs upon the rose, the effects are rather remarkable. Each egg becomes surrounded with its own cell or gall, and the whole of them become fused into one mass. The exterior of these galls is not smooth, like that of the specimens which have been described, but is covered with long, many-branched hairs, which stand out so thickly that they entirely conceal the form of the gall itself.

Réaumur, who gave much attention to galls, thought that the hairs were formed by the exudation of sap through little orifices in the growing gall, just as the web of the spider is formed by the exudation of a glutinous liquid from minute pores. This theory, however, is scarcely tenable, because sap has no power of hardening into threads when exposed to the air, and, besides, a well-defined vegetable structure is seen in the hairs, which would not be the case if they were merely hardened sap. Moreover, if the hairs were formed in this manner, they could not have the power of throwing out the tiny branchlets with which they are studded, or of ramifying like the bough of a tree, as is often the case with them.

The number of galls in a single Bedeguar is mostly very great. A specimen of average size, taken at random from the drawer in which the galls are kept, was, when fully clothed, as large as a golden pippin. When the hairy clothing was removed, its size notably diminished, and it was then seen to be composed of a large number of woody tubercles, varying much in size and shape. Their average dimensions, however, are about equal to those of an ordinary pea. The tubercles in question are fused together more or less strongly, some falling off at a slight touch, while others can not be separated without the use of the knife. There are about thirty-five of these wooden knobs.

On selecting one of the knobs, and examining it, a few very small circular holes are seen, showing that the insects have made their escape from the cells. Indeed, one or two of the insects were found entangled amid the dry and crisp hairs that surrounded the gall, and which formed a second barrier, which they could not penetrate. When, however, a sharp knife is carefully used, the woody tubercle can be laid open in several directions, and then proves to be a congeries of cells fused together into one mass, and varying from four to twenty in number, according to the size of the insect. Perhaps, on an average, ten cells may be reckoned in each knob.

In many of the cells the perfect insect may be found, the death of the rose-branch, and the consequent deprivation of sap, having so hardened the walls of the cells that the inmates have been unable to make their way out. In other cells may be seen certain odd little objects, amber-colored, hard, shining, and appearing to the unaided eye to be nearly spherical. They are about as large as dust-shot. For a long time I could not satisfy myself about them, not being able clearly to ascertain whether they were deceased insects or merely hardened sap. That they were probably of insect origin was evident from the fact that they were always found in cells which had no opening, and from which the insect had not escaped.

At last, however, one of them happened to lie on the paper so that it could be well illuminated, and then the whole mystery was unfolded. These strange little objects were the pupæ of the insects, which had died in the cells, and shriveled up into the singular forms which have been described.

The cells are of different sizes, some being more than ten times as large as others. The superior dimensions of the cell seem to be obtained at the expense of the walls, so that the large cells can be broken by the finger and thumb, while the small cells can not be opened without the knife.

The insects themselves are equally variable, some being mere dots of shining blue and green, while others are about as large as the common red ant of the gardens, but with plumper bodies. In consequence of these two facts, the large, strong-jawed insect can easily make its way through the comparatively thin walls of the large cell in which it was inclosed, while the small and necessarily weak-jawed specimens are utterly unable to pierce the walls of their cells, which are so thick that they must bore a hole equal in length to that of their whole body before they can escape into the air. Consequently, the great mass of the insects that are found in the cells are the small specimens, the larger having made their escape. I find that on an average twenty small insects are thus found in proportion to one of the larger kind.

Nothing is easier than the rearing of insects from this as well as other galls, but to decide upon the species which make them is by no means so easy a task as appears on the surface. Even should the experimenter find the right species of insect in the gauze bag, he has to go through the wearisome task of searching through the family of Cynipidæ, and identifying the species—a process which every entomologist is rather apt to postpone until the visionary period when he shall have leisure.

But it is very probable that the required insect does not make its appearance at all, and that the little hymenoptera which make their way out of the cells, or are found dead within them, are not the rightful occupants of the galls. For the Cynipidæ are as liable to parasites as other insects, and it frequently happens that from a single many-chambered gall will issue insects that sadly puzzle an amateur, as they seem to belong to at least two distinct species. The very gall which has just been described affords a good example of this fact, for in some of the chambers are specimens of the true Cynips rosæ, and in others are insects which belong to another family, the Ichneumonidæ, which, as the reader may remember, are parasites upon other insects. They have evidently introduced their eggs into the cells occupied by the larvæ of Cynips rosæ, so that the larvæ which have been hatched from these eggs have fed upon the legitimate occupants, and come to maturity in the cells that were designed for others.

Insects of totally different orders sometimes make their appearance. When I began to take to pieces the gall which has been described, I was rather surprised to find among the long hairs an empty cocoon of the Galleria moth, whose ravages have been mentioned in an earlier part of the volume. On farther dissecting the gall, no less than twelve other cocoons were found, all buried so deeply in the hairs and among the woody cells that they could not be seen until the hairy clothing was removed. A person who was entirely ignorant of entomology might naturally fancy that the moths were the architects of the gall from which they had apparently issued. How they obtained access to the galls, and on what food they lived, are two problems that I can by no means solve. The drawer in which the galls were placed is tightly closed, and all bee, wasp, and hornet combs have been so treated with corrosive sublimate that they have not been touched by the caterpillars from which the moths had been developed.