348 CELL INTELLIGENCE THE CAUSE OF EVOLUTION 



supplied by the female. In both cases the female wasp 

 first makes a nest, then drags the prey into it and lays 

 her egg or eggs upon the animals which were destined to 

 provide food for the larvae when they hatch out. The 

 female then seals up the nest and does not visit it again. 

 Now, in providing food supply for the future larvae, sev- 

 eral extraordinary instincts come into play. It is neces- 

 sary that the caterpillars, crickets, and grasshoppers 

 should be paralyzed when they are caught, otherwise the 

 wasp would have tremendous difficulty in conveying 

 them to her nest, for frequently the prey is much larger 

 than the wasp. Again, when the larvae are hatched out, 

 they are very delicate in structure, and if these compara- 

 tively large animals were able to move about freely they 

 would probably kill the larvae instead of providing them 

 with food. On the other hand, if the prey were killed 

 outright by the wasp when caught, decomposition would 

 set in in a few hours, and thus the provision made by the 

 female wasp would be useless to the larvae. This diffi- 

 culty is, however, overcome by the wasp. When Ammo- 

 phila catches a caterpillar she stings it in each of the 

 segments of the body. In the caterpillar there is a sep- 

 arate nervous centre (ganglion) in each segment, and if 

 only one or two were stung, the other segments would 

 still be able to move quite freely. In the prey of Sphex, 

 however, grasshoppers and crickets there are three 

 separate nervous centers (ganglia) which control the 

 movements of the animal. These are situated in the 

 thorax, and when the Sphex catches her prey she stings 

 it in these three separate ganglia. The result of this is that 

 the prey is rendered unable to move, but is not killed. 

 Fabre, who first described these phenomena, was- at first 

 unable to understand how it was that the prey he found 

 in the nests of these fossorial wasps did not decay, but he 



