It is indeed a superb achievement, as large as a fair-sized pumpkin. It hangs free on every side, except at the top, where various roots, mostly rootstocks of couch-grass, penetrate the thickness of the wall and fasten the nest firmly. Its shape is round wherever the softness and the homogeneous character of the ground have permitted a symmetrical excavation. In stony soil, the sphere becomes misshapen, a little more here, a little less there, according to the obstacles encountered.
A space of a hand’s breadth is always left open between the paper monument and the sides of the subterranean vault. This is the wide street along which the builders move unhindered at their continual task of enlarging and strengthening the nest. The one lane by which the city communicates with the outer world opens into it. The unoccupied space under the nest is much greater. It is rounded into a big basin which allows the general wrapper to be enlarged as fresh layers of cells are added to those above. This receptacle, shaped like the bottom of a copper, is also the great cess-pool into which the multitudinous refuse of the Wasps’-nest falls and accumulates.
The size of the cavern raises a question. The Wasps themselves dug the cellar. Of [[246]]that there is no doubt: cavities like this, so large and so accurately formed, do not exist ready-made. That the mother foundress at the beginning, working by herself and eager to get on quickly, availed herself of some chance refuge, due perhaps to the excavations of the Mole, is possible; but the rest of the work, the making of the enormous crypt, was done by the Wasps alone. Then what has become of the rubbish, the mass of earth whose bulk would be that of a cube measuring some twenty inches on every side?
The Ant erects the excavated material into a cone-shaped hillock on the threshold of her abode. With her two or three bushels of earth, what a mound would not the Wasp achieve, if heaping were her habit! But far from it: she leaves not a scrap of rubbish outside her door; everything is perfectly tidy. What has she done with the cumbrous mass?
The answer is supplied by various peaceable insects which are easy to observe. Consider a Mason-bee clearing an old nest which she proposes to use; watch a Leaf-cutter cleaning out an Earth-worm’s burrow in which to stack her leafy bags. Holding a trifle of some sort in their teeth, a shred of silky tapestry or a crumb of earth, they fly off [[247]]at a furious speed, to drop their infinitesimal load at a distance. Then they immediately face about, return to the workshop and undertake a new flight out of all proportion to the result achieved. The insect, one would think, is afraid to encumber the site by merely brushing the tiny fragments away with its feet; it must take to its wings to disperse its insignificant sweepings afar.
The Wasps work in the same manner. There are thousands and thousands of them digging at the cellar and enlarging it as the need occurs. Each carrying her particle of earth in her mandibles, they gain the outer world, fly to a distance and drop their burden, some nearer, some farther away, in all directions. Thus distributed over wide areas, the excavated earth leaves no visible trace.
The material of the Wasps’-nest is a thin, flexible brown paper, streaked with paler bands, according to the nature of the wood utilized. Made in a single, continuous sheet, according to the methods of the Median Wasp (Vespa media), this substance would constitute an indifferent protection against the cold. But, while the balloon-maker understands the art of preserving heat by means of a cushion of air contained [[248]]between several wrappers enclosed one within the other, the Common Wasp, no less versed in the laws of thermal science, arrives at the same result by different means. With her paper-pulp she manufactures broad scales which overlap loosely and are superimposed in numerous layers. The whole forms a coarse blanket, of a thick, spongy texture and well-filled with stagnant air. The temperature under such a shelter, in the hot weather, must be truly tropical.
The fierce Hornet (Vespa crabo, Linn.), chief of the Wasp clan by virtue of her strength and her warlike audacity, conforms to the same principles of the globular configuration and of air imprisoned between partition-walls. In the cavernous hollow of a willow or in the recesses of some empty granary, she manufactures a yellow, striped, very brittle cardboard, composed of an agglomeration of woody fragments. Her spherical nest is wrapped in an enclosure of broad convex scales, a sort of tiles which, welded to one another and arranged in multiple layers, leave between them wide intervals in which the air is held motionless.
To employ an athermous substance such as air, in order to check the loss of heat; to anticipate our manufacturers of eiderdown [[249]]quilts; to give the containing walls of the nest the shape that encloses the greatest capacity within the smallest wrapper; to adopt as a cell the hexagonal prism, which economizes space and material; these are scientific actions that accord with the data of our physics and geometry. We are told that the Wasp, proceeding from improvement to improvement, worked out her sensible building for herself. I cannot believe this when I see the whole nest perish, a victim to my tricks, which would easily have been baffled if the insect possessed the least power of reflection.
These wonderful architects amaze us by their stupidity in the presence of a trifling difficulty. Outside their work of the moment there is a complete absence of all lucidity such as the progressive invention of the nest would demand. Of the various tests that assure me of this, I will mention the following, which is easily made.