(2) B. oculata, Jur. The Dipteron upon which the egg is laid is generally a Sphærophoria, especially S. scripta; sometimes it is a Geron gibbosus. Further provender consisted in Stomoxys calcitrans, Pollenia ruficollis, P. rudis, Pipiza nigripes, Syrphus corollæ, Onesia viarum, Calliphora vomitoria, Echinomyia intermedia, Sarcophaga agricola, Musca domestica. The usual food was Stomoxys calcitrans, of which I have found fifty or sixty in a single burrow.

(3) Bembex tarsata, Lat. It, too, lays its egg on Sphærophoria scripta; but it also hunts Anthrax flava, Bombylius nitidulus, Eristalis æneus, E. sepulchralis, Merodon spinipes, Syrphus corollæ, Helophilus trivittatus, Zodion notatum. Its favourite prey consists in Bombylius and Anthrax. [[232]]

(4) Bembex Julii (a new species). The egg hatches either on a Sphærophoria or a Pollenia floralis, and the provender is a mixture of Syrphus corollæ, Echinomyia rubescens, Gonia atra, Pollenia floralis, P. ruficollis, Clytia pellucens, Lucilia Cæsar, Dexia rustica, Bombylius.

(5) Bembex rostrata. This is above all a captor of gadflies. It lays its egg on a Syrphus corollæ, or a Lucilia Cæsar, but then only brings to the larva large game belonging to the various kinds of Tabanus.

(6) Bembex bidentata. Another ardent hunter of gadflies. I have never seen it with other game, and do not know on what the egg is laid.

This variety of provisions shows that the Bembecids have no exclusive tastes, and attack one and all of the species of Diptera which are offered by the chances of the chase. They seem, however, to have some favourites—one species especially choosing Bombylius, another Stomoxys, and a third and fourth, Gadflies. [[233]]

[[Contents]]

XVII

HUNTING DIPTERA

After this bill of fare for Bembecids in the larva state, we must seek the motive which causes these Hymenoptera to adopt a mode of storage exceptional among Fossors. Why, instead of laying up sufficient food and dropping an egg on it, which would allow the cell to be closed at once without need of returning, does the Hymenopteron oblige itself to come and go perpetually for a fortnight from the fields to the burrow and back again, toiling every time through the sand to issue forth and hunt, or bring back prey? The explanation is that the food must be fresh—an all-important matter, for the grub absolutely refuses game which is at all high, with a hint of decay; like the larvæ of all Fossors, it must have fresh provisions—always fresh provisions.