38 WASP STUDIES AFIELD 



living Diptera larvae, four adult bee-flies, Sparnopolis 

 brez'irostris Macq. [F. Knab], the remains of eighty-five 

 more of the same, and the remains of one Lucilia caesar L. 

 [F. Knab]. Judging from the enormous amount of food 

 remains when the feeding stage of the larva was as yet far 

 from completed, and the presence of a healthy medium- 

 sized Bembix, we can only conclude that the Diptera were 

 not true parasites, since they had net attacked the larva of 

 the Bembix, but merely inquilines or impostors who depend 

 upon the mother Bewibix to work extraordinarily hard to 

 keep them, as well as her own young, supplied with meat. 

 What a terrible toll, that she must provide constantly for 

 thirty others in order that her own may live ! 



One wonders why the Dipterous larvae, so many in num- 

 ber, spared the Bembix larva, for it certainly would have 

 made a fine meal. We do not wish to speculate excessively, 

 yet it is probably only fair to breathe our suspicions on the 

 subject. If they should devour the Bembix larva, it would 

 satisfy them for only a short time, but with the demise of 

 the mother's child their further supply of food would be 

 cut off, since probably the rightful infant in the cell is the 

 stimulus for the mother to continue replenishing the food 

 supply for all of them as fast as it is exhausted. With 

 these thirty-one mouths to feed daily, it is little wonder that 

 the mother had to sacrifice all of her leisure that might have 

 been applied to improved methods of domestic economy. 



We do not pretend to say that the fly larvae knew the 

 result of this action and behaved accordingly, and numerous 

 other instances of the same kind would be required even to 

 prove that this is a case of habit or blind instinct; yet if it 

 were proved to be such, it would be no more wonderful than 

 many of the delicate adaptations already known to exist in 

 the insect world. 



