The best evidence that wasps depend upon a knowledge of the place in returning to their nests is given by the pains they take to acquire that knowledge. When Sphex ichneumonea was ready to dig her nest, she had great difficulty in finding a place that suited her. Many a spot was merely looked at and passed by, while others that seemed more attractive were left after they had been excavated for a little way. At last, the nest dug, she was ready to go out and seek for her store of provisions; and now came a most thorough and systematic study of the surroundings. The nests that had been partly made and then deserted had been left without any circling. Evidently she was conscious of the difference and meant, now, to take all necessary precautions against losing her way. She flew in and out among the plants, first in narrow circles near the surface of the ground, and now in wider and wider ones as she rose higher in the air, until at last she took a straight line and disappeared in the distance. Very often, after one thorough study of the topography of her home has been made, a wasp goes away a second time with much less circling or with none at all. If the examination of the objects about the nest makes no impression upon the wasp, or if it is not remembered, she ought not to be inconvenienced nor thrown off her track when weeds and stones are removed and the surface of the ground is smoothed over; but this is just what happens. Aporus fasciatus entirely lost her way when we broke off the leaf that covered her nest, but found it, without trouble, when the missing object was replaced. All of the species of Cerceris were extremely annoyed if we placed any new object near their nesting–places. One Ammophila refused to make use of her burrow after we had drawn some deep lines in the dust before it. The same annoyance is exhibited when there is any change made near the spot upon which the prey of the wasp, whatever it may be, is deposited temporarily. We learned from experience how important it was not to disarrange the grass or plants on such occasions. The wasps are in many cases so prudent as to conceal their booty among the leaves; and this made it very inconvenient to keep our eyes upon the captured prey, as was quite necessary if we wished to follow it on its travels. To avoid the discomfort of lying on the ground or of twisting the neck at some impossible angle for half an hour at a time, we sometimes gently moved the intercepting objects to one side; but even such a slight change cost us dear in time and patience, as it threw the wasp out of her bearings and made it difficult for her to recover her treasure. We recall one exceedingly warm day in September when we were delayed in this way for forty minutes, when she would have seized the spider and gone on her way without a pause had we not interfered. [Illustration: LOCALITY STUDY OF ASTATA BICOLOR[6]]