The Volucella 



invaders as of the big red ones. Sometimes, 

 when it enters an occupied cell, the little 

 creature is seized by the owner, the Wasp- 

 grub, which nabs it and turns it over and 

 over in its mandibles. Is this a defensive 

 bite? No, the Wasp-grub has merely blun- 

 dered, taking its visitor for a proffered 

 mouthful. There is no great harm done. 

 Thanks to its litheness, the little grub escapes 

 intact from the grip and continues its investi- 

 gations. 



It might occur to us to attribute this toler- 

 ance to some lack of penetration in the 

 Wasps' vision. What follows will unde- 

 ceive us : I place separately, in empty cells, a 

 larva of the Scalary Saperda and a Volucella- 

 larva, both of them white and selected so as 

 not to fill the cell entirely. Their presence 

 is revealed only by the paleness of the hind- 

 part, which serves as a plug to the opening. 

 A superficial examination would leave the 

 nature of the recluse undecided. The 

 Wasps make no mistake: they extirpate the 

 Saperda-grub, kill it, throw it into the rub- 

 bish-pit; they leave the Volucella-grub in 

 peace. 



The two strangers are quite well recog- 

 nized in the secrecy of the cells: one is the 

 intruder that must be turned out; the other 

 309 



