The species of the genus _Cerceris_ are numerous in Europe, and several of them are known to make burrows in the ground, and store them with beetles for the benefit of the future larvae. The beetles chosen differ in family according to the species of _Cerceris_; but it appears from the observations of Fabre and Dufour that one kind of _Cerceris_ never in its selection goes out of the limits of a particular family of beetles, but, curiously enough, will take Insects most dissimilar in form and colour provided they belong to the proper family. This choice, so wide in one direction and so limited in another, seems to point to the existence of some sense, of the nature of which we are unaware, that determines the selection made by the Insect. In the case of our British species of _Cerceris_, Smith observed _C. arenaria_ carrying to its nest Curculionidae of very diverse forms; while _C. labiata_ used a beetle—_Haltica tabida_—of the family Chrysomelidae. [Illustration: Fig. 49.—_Philanthus triangulum_ ♂. Britain.] The beetles, after being caught, are stung in the chief articulation of the body, that, namely, between the pro- and mesothorax. _Cerceris bupresticida_ confines itself exclusively to beetles of the family Buprestidae. It was by observations on this Insect that Dufour first discovered the fact that the Insects stored up do not decay: he thought, however, that this was due to the liquid injected by the wasp exercising some antiseptic power; but the observations of Fabre have shown that the preservation in a fresh state is due to life not being extinguished; the stillness, almost as if of death, being due to the destruction of the functional activity of the nerve centres that govern the movements of the limbs. {126}It has long been known that some species of _Cerceris_ prey on bees of the genus _Halictus_, and Marchal has recently described in detail the proceedings of _C. ornata_. This Insect catches a _Halictus_ on the wing, and, holding its neck with the mandibles, bends her body beneath it, and paralyses it by a sting administered at the front articulation of the neck. The _Halictus_ is subsequently more completely stunned or bruised by a process of kneading by means of the mandibles of the _Cerceris_. Marchal attaches great importance to this "malaxation"; indeed, he is of opinion that it takes as great a part in producing or prolonging the paralysis as the stinging does. Whether the malaxation would be sufficient of itself to produce the paralysis he could not decide, for it appears to be impossible to induce the _Cerceris_ to undertake the kneading until after it has reduced the _Halictus_ to quietude by stinging.