When this first cell is supplied with an egg and the necessary provisions, the Sphex walls up the entrance, but does not yet abandon her burrow. A second cell is dug beside the first and victualled in the same way; then a third and sometimes a fourth. Not till then does the Sphex shoot back into the burrow all the rubbish accumulated outside the door and completely remove all the outward traces of her work. Thus, to each burrow there are usually three cells, rarely two and still more rarely four. Now, as we ascertain when dissecting the insect, we can estimate the number of eggs laid at about thirty, which brings up to ten the number of burrows needed. On the other hand, the operations are hardly begun before September and are finished by the end of the month. The Sphex, therefore, can devote only two or three days at most to each burrow and its provisioning. No one will deny that the active little creature has not a moment to lose, when, in so short a time, she has to excavate her den, to procure a dozen Crickets, to carry them sometimes from a distance in the face of innumerable difficulties, to store them away and finally to stop up the burrow. And, besides, there are days when the wind makes hunting impossible, rainy days or even merely grey days, which cause all work to be suspended. One can readily imagine from this that the Sphex is unable to give to her buildings the perhaps permanent solidity which the Great Cerceres bestow upon their long galleries. The latter hand down from generation to generation their substantial dwellings, each year excavated to a greater depth than the last, galleries which threw me into a sweat when I tried to inspect them and which generally triumphed over my efforts and my implements. The Sphex does not inherit the work of her predecessors: she has to do everything for herself and quickly. Her dwelling is but a tent, hastily pitched for a day and shifted on the morrow. As compensation, the larvæ, who have only a thin layer of sand to cover them, are capable themselves of providing the shelter which their mother could not create: they clothe themselves in a threefold and fourfold waterproof wrapper, far superior to the thin cocoon of the Cerceres.