Lastly, thanks to its graceful oval, this cocoon 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. 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 a little light on this detail of animal psychology, I made a series of experiments which I will now describe. [40] 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.