Lastly, thanks to its graceful oval, this cocoon [[304]]seems rather the product of some elaborate manufacture than that of a grub. To any one unacquainted with the secret, the cocoons which I had built with blotting-sand might have been jewels of some unknown workmanship, great beads studded with golden spots on a lapis-lazuli ground, destined to form the necklace of a Polynesian belle. [[305]]
Chapter xvii
THE RETURN TO THE NEST
The Ammophila sinking her well at a late hour of the day leaves her work, after closing the orifice with a stone lid, flits away from flower to flower, goes to another part of the country, and yet next day is able to come back with her caterpillar to the home excavated on the day before, notwithstanding the unfamiliar locality, which is often quite new to her. The Bembex, laden with game, alights with almost mathematical precision on the threshold of her door, which is blocked with sand and indistinguishable from the rest of the sandy expanse. Where my sight and recollection are at fault, their eyes and their memory possess a sureness that is very nearly infallible. One would think that insects had something more subtle than mere remembrance, a kind of intuition for places to which we have nothing similar, in short, an indefinable faculty which I call memory, failing any other expression to denote it. There can be no name for the unknown. In order to throw if possible [[306]]a little light on this detail of animal psychology, I made a series of experiments which I will now describe.[1]
The first has for its subject the Great Cerceris, who hunts Cleonus-weevils. About ten o’clock in the morning I catch twelve females, all belonging to the same colony and at work on the same bank, busy digging burrows or victualling them. Each prisoner is placed separately in a little paper bag and the whole lot put in a box. I walk about a mile and a half from the site of the nests and then release my Cerceres, first taking care, so that I may know them later, to mark them with a white dot in the middle of the thorax, using a straw dipped in indelible paint.
The Wasps fly only a few yards away, in every direction, one here, another there; they settle on blades of grass, pass their fore-tarsi over their eyes for a moment, as though dazzled by the bright sunshine to which they have suddenly been restored; then they take flight, some sooner, some later, and all, without hesitation, make straight for the south, that is to say, for home. Five hours later I return to the common site of the nests. I am hardly there when I see two of my Cerceres with white dots working at [[307]]the burrows; soon a third arrives from the fields, with a Weevil between her legs; a fourth is not slow in following. The recognition of four out of twelve in less than fifteen minutes was enough to convince me. I thought it unnecessary to wait any longer. What four could do the others would do, if they had not already done it; and I was quite at liberty to presume that the absent eight were out hunting or else hidden in their underground galleries. Therefore, carried for a mile and a half in a direction and by a road of which they could not have taken cognizance in their paper prisons, the Cerceres, or at least some of them, had returned home.
I do not know how far the Cerceres’ hunting-grounds extend; and it is possible that they know the country more or less over a radius of a mile and a half. In that case, they would not have felt sufficiently lost at the spot to which I moved them and they would have got home by their acquired local knowledge. The experiment had to be repeated, at a greater distance and from a starting-point which the Wasp could not be suspected of knowing.
I therefore take nine female Cerceres from the same group of burrows that supplied me in the morning. Three of them had just been subjected to the previous test. They were again [[308]]carried in a dark box, each insect enclosed in its paper bag. The starting-point selected is the nearest town, Carpentras, which lies at about two miles from the burrow. I am to release my insects not among the fields, as on the first occasion, but absolutely in the street, in the centre of a crowded neighbourhood, where the Cerceres, with their rustic habits, had certainly never penetrated. As the day is already far advanced, I postpone the experiments; and my captives spend the night in their prison-cells.
Next morning, at about eight, I mark them on the thorax with two white spots, to distinguish them from yesterday’s lot, who were marked with only one; and I set them free, one after the other, in the middle of the street. Each Cerceris released first shoots straight up between the two rows of houses, as though to escape as soon as possible from the narrow street and gain the spacious horizons; then, rising above the roofs, she at once darts away vigorously towards the south. And it was from the south that I brought them; it is in the south that their burrows are. Nine times, with nine prisoners, freed one after the other, I had this striking instance of the way in which the insect stranded far from home takes without hesitation the right direction for returning to the nest.