The Descent of Man

213.) The ocelli are absent in the females of certain
insects, as in the Mutillidae; and here the
females are likewise wingless. But we are chiefly
concerned with structures by which one
male is enabled to conquer another, either in
battle or courtship, through his strength, pugnacity,
ornaments, or music. The innumerable
contrivances, therefore, by which the male is
able to seize the female, may be briefly passed
over. Besides the complex structures at the apex
of the abdomen, which ought perhaps to be
ranked as primary organs (2. These organs in
the male often differ in closely-allied species,
and afford excellent specific characters. But
their importance, from a functional point of
view, as Mr. R. MacLachlan has remarked to
me, has probably been overrated. It has been
suggested, that slight differences in these organs
would suffice to prevent the intercrossing
of well-marked varieties or incipient species,
and would thus aid in their development. That
this can hardly be the case, we may infer from