Chap. VII. 
NEUTEE INSECTS. 
237 
in the ordinary state, I should have unhesitatingly 
assumed that all its characters had been slowly acquired 
through natural selection; namely, by an individual 
having been born with some slight profitable modifi¬ 
cation of structure, this being inherited by its offspring, 
which again varied and were again selected, and so 
onwards. 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 modifications of structure or instinct to its pro¬ 
geny. It may well be asked how is it possible to recon¬ 
cile this case with the theory of natural selection ? 
First, let it be remembered that we have innumerable 
instances, both in our domestic productions and in those 
in a state of nature, of all sorts of differences of struc¬ 
ture which have become correlated to certain ages, and 
to either sex. We have differences correlated not only 
to one sex, but to that short period alone when the re¬ 
productive system is active, as in the nuptial plumage of 
many birds, and in the hooked jaws of the male salmon. 
We have even slight differences in the horns of different 
breeds of cattle in relation to an artificially imperfect 
state of the male sex; for oxen of certain breeds have 
longer horns than in other breeds, in comparison with 
the horns of the bulls or cows of these same breeds. 
Hence I can see no real difSiculty in any character 
having become correlated with the sterile condition of 
certain members of insect-communities: the difficulty 
lies in understanding how such correlated modifications 
of structure could have been slowly accumulated by 
natural selection. 
This difficulty, though appearing insuperable, is 
lessened, or, as I believe, disappears, when it is re¬ 
membered that selection may be applied to the family, 
as well as to the individual, and may thus gain the 
