CHAPTER XX 



THE MODERN THEORY OF INSTINCT 



THE larvae of the various Hunting 

 Wasps require their prey to be inca- 

 pable of movement, so that there may be no 

 resistance on the victim's part, which would 

 be a source of danger to the fragile egg and, 

 later, to the grub. Moreover, for all its 

 lethargy, it must still be alive; for the grub 

 would refuse to feed on a corpse. The fare 

 provided must be fresh meat and not pre- 

 served stuff. I have already laid stress on 

 these two antagonistic conditions, immobil- 

 ity and life, and enlarged on them so fully 

 that I need hardly dwell upon them for a 

 second time. I have shown how the Wasp 

 realizes them by the medium of a paralysis 

 which destroys movement and leaves the or- 

 ganic principle of life intact. With a skill 

 which our most famous vivisectors would 

 envy, the insect drives its poisoned sting into 

 the nerve-centres, the seat of muscular inci- 

 tation. The operator confines herself to one 

 stroke of the lancet, or else gives two, three 

 385 



