Here we have intelligent behaviour rising to a level to which some would apply the term rational. For the act may be held to afford evidence of the perception of the relation of the means employed to an end to be attained, and some general conception of purpose. In this section, which deals with description of behaviour based on observation, the psychological explanation cannot be discussed. Similar indications of deliberate action may be held to be afforded by the sometimes elaborate “locality studies” which these insects seem to make,--by the “care that is taken by wasps to acquaint themselves with the surroundings of their nests.” A _Sphex_, for example, which had partially made and then abandoned several nests, left them without any locality study; but when she had completed a nest in a suitable spot she made “a most thorough and systematic study of the surroundings. She flew in and out among the plants, first in narrow circles near the surface of the ground, and then 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.” Another species (_Cerceris deserta_) “has the habit of making a number of half circles in front of the nest, and then, after rising a little higher, of flying several times completely round it.” The method of procedure is, it seems, so normal to the species that it is probably founded on an instinctive basis. Dr. and Mrs. Peckham, in commenting on their observations, say:[54] “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.” For convenience of observation they “sometimes gently moved intercepting objects to one side, but even such a slight change threw the wasp out of her bearings, and made it difficult for her to recover her treasure.” Where wasps form a number of nests in a small plot of ground, as in the case of _Bembex_, each knows and returns to its own hole, as was proved by Dr. Peckham, who marked the insects and their nests with paint.