88 Darwin, and after Darwin. 



be sought in consciously intelligent adjustments on 

 the part of ancestors. 



Thus, to give only one example, a species of 

 Sphex preys upon caterpillars, which it stings in 

 their nerve-centres for the purpose of para'yzing, 

 without killing them. The victims, when thus ren- 

 dered motionless, are then buried with the eggs of 

 the Sphex, in order to serve as food for her larvae 

 which subsequently develop from these eggs. Now, 

 in order thus to paralyze a caterpillar, the Sphex has 

 to sting it successively in nine minute and particular 

 points along the ventral surface of the animal and 

 this the Sphex unerringly does, to the exclusion 

 of all other points of the caterpillar's anatomy. Well, 

 such being the facts according to M. Fabre, who 

 appears to have observed them carefully it is con- 

 ceivable enough, as Darwin supposed l , that the 

 ancestors of the Sphex, being like many other hymen- 

 opterous insects highly intelligent, should have 

 observed that on stinging caterpillars in these particular 

 spots a greater amount of effect was produced than 

 could be produced by stinging them anywhere else ; 

 and, therefore, that they habitually stung the cater- 

 pillars in these places only, till, in course of time, this 

 originally intelligent habit became by heredity instinc- 

 tive. But now, on the other hand, if we exclude the 

 possibility of this explanation, it appears to me in- 

 credible that such an instinct should ever have been 

 evolved at all ; for it appears to me incredible that 

 natural selection, unaided by originally intelligent 

 action, could ever have developed such an instinct 



1 For details of his explanation of this particular case, for which 

 I particularly inquired, see Mental Evolution in Animals, pp. 301-2. 



