These observations show that the two species of wasps with which we experimented have no sense of direction in the form of a mysterious additional sense, nor yet in the form of a power by which they keep a register of the turns and changes in a journey and are thus able to retrace their way. Our cage was of wire, and so open that they could see all about, as we carried them from place to place; yet when they flew out, they most frequently started in a wrong direction and toward a point that we had not passed. In many instances, however, these wasps returned to the nest, and it seems highly probable that as they rose higher and higher into the air, circling as they went, they discovered some lofty treetop or other object that had before served them as a landmark, and that in this way they were able to make their way home. Bee–keepers know that if young workers which, in strong hives, pass the first ten or fifteen days of their lives in feeding the larvæ without going abroad, are taken out and set free only a short distance from home, they are unable to find their way back, and perish, while those that have passed beyond the nursing stage and have begun to do outside work may be carried long distances away and still readily regain the nest. With the solitary wasps we attacked the problem from the other end. We observed what the social wasps did in attempting to return to the nest; with the solitaries, we watched them when, after making the nest, they prepared to leave it to go out into the fields or woods in search of food or prey, thinking that the procedure of different species under these circumstances would afford a clue to the faculty upon which they depended to find their way about. If they were furnished with an innate sense of direction they would not need to make a study of the locality of the nest in order to find the way back, but if they were without this sense it would be only common prudence to take a good account of their bearings before going far afield. The sight of a bee or a wasp returning to its home from some far distant spot, without hesitation or uncertainty, is indeed marvelous. When we saw our first Ammophila perform this feat we were filled with wonder. How was it possible for her to hunt for hours, in all directions, far and wide, and then return in a direct line to a nest which had been so carefully covered over that every trace of its existence was obliterated?