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 [[156]]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.
Poor, desperate thing, why don’t you copy your young sister? Do what the little larva did just now: build an awning with particles taken from the wall of your house; and your liquid putty will do well on that spongy scaffolding! The large grub, trusting to its trowel, does not think of that method. It exhausts itself, without any appreciable result, in trying to effect repairs which the little grub managed most ingeniously. What the baby knew how to do the big larva no longer knows.
Insect industry has instances like this of professional methods employed at certain periods and then abandoned [[157]]and utterly forgotten. A few days more or less make changes in the creature’s talents. The tiny grub, devoid of cement, has bricks to fall back upon: the big larva, rich in putty, scorns to build, or rather no longer knows how, though it is even better-endowed than the youngster with the necessary tools. The strong one no longer remembers what as a weakling he so well knew how to do, only a few days before. A poor power of recollection, if indeed there be such a power under that flat skull! However, in the long run and thanks to the evaporation of the ejected materials, the short-memoried plumber ends by stopping up the window. Nearly half a day has been spent in trowel-work.
The idea occurs to me to try whether the mother will come to the distressed one’s aid in like circumstances. We have seen her diligently restoring the ceiling which I smashed above the egg. Will she do for the big grub what she did for the sake of the germ? Will she repair the torn pill in which the plasterer is helplessly floundering?
To make the experiment more conclusive, I select pills that do not belong to the mother entrusted with the work of restoration. I picked them up in the fields. They are far from regular, are all dented because of the stony soil on which they lay, a soil not easily convertible into a roomy workshop and consequently unsuited to exact geometry. They are moreover encrusted with a reddish rind, due to the ferruginous sand in which I packed them in order to avoid dangerous jolting on the road. In short, they differ a good deal from those elaborated in a jar, with plenty of space around them and on a clean support, pills which are perfect ovoids, free from earthy stains. In the top of two of them I make an opening which the grub, faithful to its methods, at once strives to stop up, but [[158]]without success. One, stored away under a bell-glass, will serve me as a witness. The other I place in a jar where the mother is watching her cradles, two splendid ovoids.
I have not long to wait. An hour later I raise the cardboard screen. The Copris is on the strange pill and so busily engaged that she pays no attention to the daylight admitted. In other, less urgent circumstances, she would at once have slipped down and taken shelter from the troublesome light; this time, she does not move and imperturbably continues her work. Before my eyes she rakes away the red crust and uses the scrapings from the cleansed surface to spread over and solder the breach. It is hermetically sealed in a very short space of time. I stand amazed at the insect’s skill.
Well, while the Copris is restoring a pill that does not belong to her, what is the grub that owns the other doing in the bell-glass? It continues to kick about hopelessly, vainly lavishing cement that is incapable of setting. Put to the test in the morning, it does not succeed until the afternoon in closing the aperture; and then the job is anything but well done. The borrowed mother, on the other hand, has not taken twenty minutes to remedy the accident most excellently.
She does even more. After the most important part is finished and the afflicted grub succoured, she stands all day, all night and the next day on the newly-closed pill. She brushes it daintily with her tarsi to get rid of the layer of earth; she obliterates the dents, smooths the rough places and adjusts the curve, until from a shapeless and soiled pill it becomes an ovoid vying in precision with those which she had already manufactured in her glass jar. [[159]]