1 14 The Hunting Wasps 



presumed in the case of the Sphex-wasps, whom 

 I have seen so faithful to an exclusive victim, 

 always the same for each of them, and who 

 moreover find, among the Orthoptera, groups 

 that differ very widely in shape. Nevertheless, 

 I have had the good fortune to come upon one 

 case, one onl}^ of complete change in the larva's 

 nourishment ; and I record it the more willingly 

 in the Sphegian archives inasmuch as such facts, 

 scrupulously observed, will one day form 

 foundation-stones for any one who cares to 

 build up the psychology of instinct on a solid 

 basis. 



Here are the facts. The scene is enacted 

 on a towing-path along the Rhone. On one 

 side is the mighty stream, with its roaring 

 waters ; on the other is a thick hedge of osiers, 

 willows, and reeds ; between the two runs a 

 narrow walk, with a carpet of fine sand. A 

 Yellow-winged Sphex appears, hopping along, 

 dragging her prey. What do I see ! The prey 

 is not a Cricket, but a common Acridian, a 

 Locust ! And yet the Wasp is really the 

 Sphex with whom I am so familiar, the Yellow- 

 winged Sphex, the keen Cricket-huntress. I 

 can hardly believe the evidence of my own eyes. 



The burrow is not far off : the insect enters 

 it and stores away the booty. I sit down, de- 

 termined to wait for a new expedition, to wait 



