It seems to be the habit of some _Pompilus_ to procure a victim before they have secured a place for its reception; and Fabre took advantage of this fact, and made very interesting observations on some points of the instinct of these wasps. Having found a _Pompilus_ that, after having caught a spider and paralysed it, was engaged in making a retreat for its reception, he abstracted the booty, which was deposited at the top of a small tuft of vegetation near to where the _Pompilus_ was at work. In this case the burrow in course of preparation was subterranean, and was formed by the _Pompilus_ itself, which therefore could not, while it was engaged underground, see what took place near it. It is the habit of the wasp to leave its work of excavation from time to time, and to visit the prey as if to assure itself of the safety of this object, and to enjoy the satisfaction of touching it with the mouth and palping it. Desirous of testing the wasp's memory of locality, Fabre took the opportunity, while the Insect was working at the formation of its burrow, of removing, as we have said, the booty from the place where it had been deposited, and putting it in another spot some half-yard off. In a short time the _Pompilus_ suspended work and went straight to the spot where it had deposited its property, and finding this absent, entered on a series of marches, counter-marches, and circles round the spot where it had left the prey, as if quite sure that this was really the place where the desired object ought to be. At last convinced that the paralysed prey was no longer where it had been placed, the _Pompilus_ made investigations at a greater distance and soon discovered the spider. Fabre recounts that its movements then appeared to indicate astonishment at the change of position that it thus ascertained to have occurred. The wasp, however, soon satisfied itself that this was really the very object it was seeking, and seizing the spider by the leg slightly altered its position by placing it on the summit of a small tuft of vegetation; this latter proceeding being apparently always carried out by this species of _Pompilus_. Then it returned to its excavation, and Fabre again removed the spider to a third spot; the wasp when it next rested from its work made its way {104}immediately to the second spot, where it had last left the spider, thus showing that it possessed an accurate memory for locality; the wasp was very much surprised at the absence of the valued prize and persisted in seeking it in the immediate vicinity without once returning to the place where it had been first located. Fabre repeated this manoeuvre five times, and the _Pompilus_ invariably returned at once to the spot where it had last left its prey. The acute memory for localities displayed by this Insect seems to be more or less general throughout the Aculeate Hymenoptera, and is of very great importance to them. The power of finding the object appears to depend on