It is possible that I did not rear my larva with the wholesome frugality and the wise [[267]]economy which the mother would have shown; there was perhaps some waste in the daily provisions served all at one time and left entirely to the grub’s discretion. In some respects I feel inclined to believe that things do not happen just like that in the maternal cell, for my notes contain such details as the following. In the alluvial sands of the Durance I discover a burrow which the Wasp (Bembex oculata) has just entered with a Sarcophaga agricola. Inside I find a larva, numerous fragments and a few whole Flies, namely, four Sphærophoria scripta, one Onesia viarum and two Sarcophaga agricola, including the one which the Bembex has just brought along before my eyes. Now it is worthy of remark that half of this game, namely, the Sphærophoriæ, is right at the end of the cell, under the larva’s very teeth, whereas the other half is still in the passage, on the threshold of the cell, and therefore beyond the reach of the grub, which is unable to change its position. It seems to me then that, when game is plentiful, the mother lays her captures on the threshold of the cell for the time and forms a reserve on which she draws as and when necessary, especially on rainy days when all labour is at a standstill.
Thus practised with economy, the distribution of food would save a waste which I was not [[268]]able to prevent with my larva, treated I dare say too sumptuously. I therefore lower the figure obtained and reduce it to some sixty pieces, of middling size, between that of the House-fly and of the Eristalis tenax. This would about represent the number of Flies supplied by the mother to the larva when the prey is of a moderate size, as is the case with all the Bembex of my district except the Rostrate Bembex (B. rostrata) and the Two-pronged Bembex (B. bidentata), who have a preference for Gad-flies. With them, the number of victims would be from one to two dozen, according to the size of the Fly, which varies greatly in the different species of Gad-flies.
To avoid reopening this question of the nature of the provisions, I will here give a list of the Flies observed in the burrows of the six species of Bembex that form the subject of this essay.
1. Bembex olivacea, Rossi. I only once saw this species, at Cavaillon, feeding on Green-bottles. The five other species are common in the Avignon neighbourhood.
2. Bembex oculata, Jur. The Fly carrying the egg is most often a Sphærophoria, especially S. scripta; sometimes it is a Geron gibbosus. The later provisions include Stomoxys calcitrans, Pollenia ruficollis, P. rudis, Pipiza nigripes, [[269]]Syrphus corollæ, Onesia viarum, Calliphora vomitoria,[5] Echinomyia intermedia, Sarcophaga agricola and Musca domestica.[6] The usual fare consists of Stomoxys calcitrans, of which I have many a time found fifty or sixty in a single burrow.
3. Bembex tarsata, Lat. This one also lays her egg on Sphærophoria scripta. She next hunts: Anthrax flava, Bombylius nitidulus, Eristalis æneus, E. sepulchralis, Merodon spinipes, Syrphus corollæ, Helophilus trivittatus and Zodion notatum. Her favourite game consists of Bombylii, or Bee-flies, and Anthrax-flies.[7]
4. Bembex Julii (sp. nov.). The egg is laid on a Sphærophoria or on a Pollenia floralis. The provisions are a hotchpotch of Syrphus corollæ, Echinomyia rubescens, E. intermedia, Gonia atra, Pollenia floralis, P. ruficollis, Clytia pellucens, Lucilia Cæsar, Dexia rustica and Bombylius.
5. Bembex rostrata, Fab. This is preeminently a consumer of Gad-flies. She lays her egg on a Syrphus corollæ or a Lucilia Cæsar, after which she feeds her larva exclusively on big game belonging to the various species of the genus Tabanus. [[270]]
6. Bembex bidentata, V. L. Another ardent huntress of Gad-flies. I have never seen her pursue other game and I do not know on what Fly the egg is laid.
This great variety of provisions shows that the Bembex have no exclusive tastes and fall upon any species of Flies, indifferently, which the hazards of the chase place within their reach. They seem nevertheless to entertain a few preferences. Thus one species feeds more particularly on Bee-flies, a second on Stomoxys-flies, a third and a fourth on Gad-flies. [[271]]