884 THE ORIGIN OF SPECIES 



which at firet 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 difiEer 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 ani- 

 mals 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 an- 

 nually 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 oi 

 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 be- 

 tween 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 char- 

 acters had been slowly acquired through natural selec- 

 tion; namely, by individuals having been born with slight 

 profitable modifications, which were inherited by the 

 offspring; and that these again varied and again were 



