2G8 A BOOK OF INSECTS 



dodges about the entrance until the enraged occupant is 

 induced to show itself, when the wasp instantly grips one 

 of its legs with her jaws and pulls with all her might. If 

 the spider proves the stronger, the insect relinquishes her 

 hold and seeks another den, where the same tactics are 

 repeated. Sooner or later she manages to drag a spider 

 from its stronghold, when she pounces upon it and inflicts 

 the coup de grace with her sting. 



Most digger-wasps simply close up their cells after the 

 egg has been laid, and never return to them again. The 

 mother instinctively stores a sufficiency of food for the 

 needs of the grub. But wasps of the genus Bembex and 

 their allies are exceptions. Unfortunately there is no 

 British representative of this interesting group, but the 

 habits of certain European and North American species 

 have been carefully investigated. The nests are formed 

 in dry, sandy spots. The prey consists of Diptera of 

 various kinds ; but instead of laying up a heap of carcases 

 the mother wasp glues her egg to the side of one small 

 fly, and then closes the entrance to the burrow. Two or 

 three days later the egg hatches, and the larva consumes 

 the soft parts of the fly. Meanwhile the mother remains 

 in the vicinity, and at the crucial moment brings another 

 fly slightly larger than the first. She does this again and 

 again for about a fortnight, until her offspring refuses 

 food and is ready to spin its cocoon. In the case of 

 Bembex rostrata Fabre found that from fifty to eighty 

 flies may be required before the grub shows signs of reple- 

 tion. A small Syrphus or a bright green flesh-fly is 

 generally utilised for the first meal, but afterwards the 

 game consists of targe blood-sucking gad-flies {Tabanidce). 

 Whether a Bembex ever sets up more than one nursing 

 establishment at the same time is a question which has 

 not yet been settled. The American species [Bembex 



