XVI 



THE BEMBEX 225 



This peculiarity of beginning to lay in food by a 

 single small piece of game is not peculiar to Bembex 

 rostrata ; all the other species do the same. Open 

 any cell after the egg is laid, and you always find it 

 glued to the side of a Dipteron — all the food there is ; 

 moreover, this first ration is invariably small, as if the 

 mother had sought some specially tender mouthful 

 for her frail nursling. Another motive, the fresh- 

 ness of the food, may also have guided her choice. 

 Later we will look further into the matter. This 

 first ration — always a moderate one — varies much, 

 according to the frequency of such or such a kind 

 of game in the neighbourhood. It is sometimes a 

 Lucilia Caesar, sometimes a Stomoxys, or some small 

 Eristalis, or a delicate Bombylius clad in black velvet, 

 but the commonest is a Spha^rophoria with a slender 

 abdomen. This fact (and it has no exception) of storing 

 the nest with but a single Dipteron, — a ration far too 

 meagre for a larva with a voracious appetite, — at once 

 puts us on the track of the most remarkable habit 

 of the Bembecidse. Hymenoptera whose larvae live 

 on prey heap into each cell the whole number of 

 victims needed by the grub, which is hatched and 

 lives alone, — an egg having been laid on one fly and 

 the dwelling closed up. The larva has before it 

 its whole store of food. But the Bembex is an 

 exception to this rule. First a head of game is 

 brought to the cell and an egg dropped on it. Then 

 the mother leaves the burrow, which closes of its 

 own accord ; besides which she takes care to rake the 

 surface smooth, and hide the entrance from every 

 eye but her own. 



Two or three days pass : the egg hatches and 

 Q 



