In the digging and closing of her burrow—her nesting-habits, as we may call them—our _Ammophila_ is almost as interesting to watch as in her mode of proceeding with caterpillars, though here a certain well-known stimulus to human enjoyment which I need not enlarge upon is wanting. Having found a convenient spot for her nursery, she digs, with her mandibles and front pair of legs, a little tunnel in the ground, to about the length of her own body, and at the end of it hollows out a round chamber or cavern just large enough to make comfortable quarters for a pair of invalid caterpillars—a hospital for incurables, we may call it to begin with, but soon to become their tomb. Having dug to about her middle, the wasp backs out, with a little pellet of collected earth held firmly in her mandibles. With this she flies to a little distance and then, letting it drop, alights on the ground and takes a little rest before returning to continue her work. She may either fly or run back, for her legs are as highly developed as her wings—she is in fact a very perfect athlete. The process of excavation is now continued, there is more burrowing, more flying away with the earth dug out, and before long the nursery-vault is completed. The next thing is to find caterpillars for it, but before flying away to look for one, _Ammophila_ carefully conceals the entrance to her tunnel with pellets of earth, which she often brings from a distance, and will not be satisfied with unless they seem well adapted for their purpose. At last, when the aperture is both blocked and hidden, she starts off upon the still more important undertaking which has been already described, and after a longer or shorter interval—if her quest is successful—returns with a nicely stung caterpillar. As two are required there must be another journey and another stopping up of the burrow, before the final one, which is of a more solid nature, occupying, sometimes, as much as twenty minutes. In thus bringing her labours to a conclusion, _Ammophila_ often shows a wonderful degree of intelligent foresight—foresight we must term it if we admit the intelligence; for sometimes she will drag a leaf over the entrance to the tunnel, though now filled in, or taking a stone as large as her head in her mandibles, will pound down the earth with it to make it firm and compact.[87]