The size of the cavern raises a question. The Wasps themselves dug the cellar. Of 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 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 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.