XI 



THE SCIENCE OF INSTINCT 



I HAVE no doubt that in order to paralyse her prey, 

 Sphex occitanica follows the method of the one that 

 hunts grasshoppers, plunging her sting repeatedly 

 into the breast of the ephippiger in order to reach 

 the thoracic ganglia. She must be familiar with the 

 operation of injuring the nerve centres, and I am 

 assured beforehand of her consummate skill in the 

 learned operation. It is an art familiar to all the 

 predatory Hymenoptera who bear a poisoned dagger, 

 and it is not given them for nothing. But I must own 

 that I have never yet beheld the deadly manoeuvre, 

 thanks to the solitary life of this Sphex. 



When a number of burrows are made and then 

 provisioned on some common ground, one has only 

 to wait there to see now one insect return from the 

 chase, now another, with her prey, and it is easy to 

 substitute a live victim for the one sacrificed, renew- 

 ing the experiment at will. Besides, the certainty 

 that the subjects for experiment will not fail when 

 wanted allows everything to be prepared beforehand, 

 while with S. occitanica these conditions of success do 

 not exist. To set out and look for her with one's 



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