370 OBJECTION'S TO THE THEORY 



they could hardly have been acted on by natural selection; 

 cases of instincts almost identically the same in animals so 

 remote in the scale of nature that we cannot account for 

 their similarity by inheritance from a common progenitor, 

 and consequently must believe that they were independ- 

 ently acquired through natural selection. I will not here 

 enter on these several cases, but will confine myself to one 

 special difficulty, which at first appeared to me insuperable, 

 and actually fatal to the whole theory. I allude to the 

 neuters or sterile females in insect communities; for these 

 neuters often differ widely in instinct and in structure from 

 both the males and fertile females, and yet, from being 

 sterile, they cannot propagate their kind. 



The subject well deserves to be discussed at great length, 

 but I will here take only a single case, that of working or 

 sterile ants. How the workers have been rendered sterile 

 is a difficulty; but not much greater than that of any 

 other striking modification of structure; for it can be 

 shown that some insects and other articulate animals 

 in a state of nature occasionally become sterile; and if 

 such insects had been social, and it had been profitable 

 to the community that a number should have been 

 annually born capable of work, but incapable of procrea- 

 tion, I can see no especial difficulty in this having been 

 effected through natural selection. But I must pass over 

 this preliminary difficulty. The great difficulty lies in 

 the working ants differing widely from both the males 

 and the fertile females in structure, as in the shape 

 of the thorax, and in being destitute of wings and some- 

 times _ of eyes, and in instinct. As far as instinct 

 alone is concerned, the wonderful difference in this respect 

 between the workers and the perfect females would have 

 been better exemplified by the hive-bee. If a working ant 

 or other neuter insect had been an ordinary animal, I 

 should have unhesitatingly assumed that all its characters 

 had been slowly acquired through natural selection; 

 namely, by individuals having been born with slight profit- 

 able modifications, which were inherited by the offspring, 

 and that these again varied and again were selected, and so 

 onward. But with the working ant we have an insect 

 differing greatly from its parents, yet absolutely sterile; so 

 that it could never have transmitted successively acquired 



