I have now explained how, I believe, the wonderful fact of two distinctly defined castes of sterile workers existing in the same nest, both widely different from each other and from their parents, has originated.

We can see how useful their production may have been to a social community of ants, on the same principle that the division of labour is useful to civilised man.

Ants, however, work by inherited instincts and by inherited organs or tools, while man works by acquired knowledge and manufactured instruments.