xx THE SCIENCE OF INSTINCT 159 



might suppose that the nerve centre struck was the 

 lower part of the oesophagean collar, but the persist- 

 ence of movement in the mouthpieces, mandibles, 

 jaws, and palpi, animated by this source of nerve 

 power, shows that this is not so. Through the neck 

 the Sphex simply reaches the thoracic ganglia, or at 

 least the first, more easily attainable through the 

 thin skin of the neck than through the integuments 

 of the chest. 



All is over. Without one convulsion or sign of pain 

 the ephippiger is rendered henceforward an inert 

 mass. For the second time I deprived the Sphex 

 of the subject operated on, replacing it by the second 

 female at my disposal. The same manoeuvres were 

 followed by the same result. Three times, almost 

 without a pause, the Sphex repeated her skilled 

 surgery, first on her own capture, then on those 

 exchanged by me. Will she do so a fourth time on 

 the male which I still have ? It is doubtful, not 

 that she is weary, but because the game does not 

 suit her. I have never seen a Sphex with any but 

 female prey, which, filled as they are with eggs, are 

 the favourite food of the larvae. My suspicion was 

 well founded. Deprived of her third capture, she 

 obstinately refused the male which I offered her. 

 She ran hither and thither with hurried steps, seeking 

 her lost prey. Three or four times she approached 

 the ephippiger, walked round it, cast a disdainful 

 glance at it, and finally flew away. This was not 

 what her larvae wanted. Experiment reiterated it 

 after twenty years' interval. 



The three females, two stabbed under my eyes, 

 remained mine. All the feet were quite paralysed, 



