Formica flava has larger and smaller workers, with some few of intermediate
size; and, in this species, as Mr. F. Smith has observed, the larger
workers have simple eyes (ocelli), which, though small, can be plainly
distinguished, whereas the smaller workers have their ocelli rudimentary.
Having carefully dissected several specimens of these workers, I can affirm
that the eyes are far more rudimentary in the smaller workers than can be
accounted for merely by their proportionately lesser size; and I fully
believe, though I dare not assert so positively, that the workers of
intermediate size have their ocelli in an exactly intermediate condition.
So that here we have two bodies of sterile workers in the same nest,
differing not only in size, but in their organs of vision, yet connected by
some few members in an intermediate condition. I may digress by adding,
that if the smaller workers had been the most useful to the community, and
those males and females had been continually selected, which produced more
and more of the smaller workers, until all the workers were in this
condition; we should then have had a species of ant with neuters in nearly
the same condition as those of Myrmica. For the workers of Myrmica have
not even rudiments of ocelli, though the male and female ants of this genus
have well-developed ocelli.
I may give one other case: so confidently did I expect occasionally to
find gradations of important structures between the different castes of
neuters in the same species, that I gladly availed myself of Mr.
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