Formica flava has larger and smaller workers, with some 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
proportionally 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 we here 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 had come to be
in this condition; we should then have had a species of ant with
neuters very nearly in the same condition with 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 to find
gradations in important points of structure between the different
castes of neuters in the same species, that I gladly availed myself of
Mr.
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