In one of my cages I rob a Sacred Beetle of her round pill, lately fashioned and briskly rolled. I strip it at one point of its earthy layer and into this clean point I drive the blunt end of a pencil, making a hole a third of an inch deep. I install a newly-hatched Copris-grub in it. The youngster has not yet taken the least refreshment. It is lodged in a cell which in no respect differs from the rest of the mass. There is no creamy coating, whether disgorged by the mother or merely oozing through. What will result from this change of quarters? Nothing untoward. The larva develops and thrives quite as well as in its native cell. Therefore, when I first started, I was the victim of an illusion. The delicate wash which nearly always covers the egg-chamber in the Dung-beetles’ work is simply an exudation. The grub may be all the better for it, when taking its first mouthfuls; but it is not indispensable. To-day’s experiment confirms the fact. The grub subjected to this test was put into an open pit. Things cannot remain in this condition. The absence of ceiling is irksome to the young larva, which loves darkness and tranquillity. How will it set to work to build its roof? The mortar-trowel cannot be used as yet, for materials are lacking in the knapsack which so far has done no digesting. Novice though it be, the little grub has its resources. Since it cannot be a plasterer, it becomes a bricklayer. With its legs and mandibles it removes particles from the walls of its cell and comes and places them one by one on the rim of the well. The defensive work makes rapid progress and the assembled atoms form a vault. It has no strength about it, I admit; the dome falls in if I merely breathe on it. But soon the first mouthfuls will be swallowed; the intestines will fill; and, well supplied, the grub will come and consolidate the work by injecting mortar into the interstices. Properly cemented, the frail awning becomes a solid ceiling. Let us leave the tiny grub in peace and consult other larvæ which have attained half their full growth. With the point of my penknife I pierce the pill at the upper end; I open a window a few millimetres square. The grub at once appears at the casement, anxiously enquiring into the disaster. It rolls itself over in the cell and returns to the opening, this time, however, presenting its wide, padded trowel. A jet of mortar is discharged over the breach. The product is a little too much diluted and of inferior quality. It runs, it flows in all directions, it does not set quickly. A fresh ejaculation follows and another and yet another, in swift succession. Useless pains! In vain the plasterer tries again, in vain it struggles, gathering the trickling material with its legs and mandibles: the hole refuses to close. The mortar is still too fluid.