LIMITATION OF INSTINCT. 253 



Fabre drove her away, and took out both the Ephippi- 

 gera and the egg. He then allowed the Sphex to return. 

 She went down into the empty cell, and though she 

 must have known that the grasshopper and the egg 

 were no longer there, yet she proceeded calmly to stop 

 up the orifice just as if nothing had happened. 



The genus Sphex paralyzes its victims and provisions 

 its cell once for all. Bembex, on the contrary, as 

 already mentioned, kills the insects on which its young 

 are to feed, and, perhaps on this account, brings its 

 young fresh food (mainly flies) from time to time. 

 But while the Bembex thus preys on some flies, there 

 are others which avenge their order. The genus 

 Miltogramma lays its eggs in the cell of the Bembex ; 

 and, though there seems no reason why the Bembex, 

 which is by far the stronger insect, should tolerate this 

 intrusion, which, moreover, she shows unmistakably to 

 be most unpalatable, she never makes any attack on 

 her enemy. Nay, when the young of the Miltogramma 

 are hatched, so far from being killed or removed, these 

 entomological cuckoos are actually fed until they reach 

 maturity. ISTevertheless, it seems contrary to etiquette 

 for the fly to enter the cell of the Bembex ; she watches 

 the opportunity when the latter is in the cell and is 

 dragging down the victim. Then is the Miltogramma's 

 oj)portunity ; she pounces on the victim, and almost 

 instantaneously lays on it two or three eggs, which are 

 then transferred, with the insect on which they are to 

 feed, to the cell. 



It is remarkable how the Bembex remembers (if one 

 may use such a word) the entrance to her cell, covered 

 as it is with sand, exactly to our eyes like that all 

 round. On the other hand, M. Fabre found that if he 



