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 larvae 

 of all Fossors, it must have fresh provisions — always 

 fresh provisions. 



We have seen in the case of the Cerceris, Sphex, 

 and Ammophila how the mother resolves the feeding 

 problem, by placing beforehand in the cell a sufficient 

 quantity of game, and also that of keeping it for weeks 

 perfectly fresh — nay, almost alive, though motionless 

 — in order to secure the safety of the grub which 



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