henomena, beginning with a general harmony and adaptation of tint in
autumn and winter moths and in arctic and desert animals, and ending
with those complete cases of detailed mimicry which not only deceive
predacious animals, but puzzle the most experienced insect collectors
and the most learned entomologists.

_Mimicry by Female Insects only._

But there is yet another series of phenomena connected with this
subject, which considerably strengthens the view here adopted, while it
seems quite incompatible with either of the other hypotheses; namely,
the relation of protective colouring and mimicry to the sexual
differences of animals. It will be clear to every one that if two
animals, which as regards "external conditions" and "hereditary
descent," are exactly alike, yet differ remarkably in colouration, one
resembling a protected species and the other not, the resemblance that
exists in one only can hardly be imputed to the influence of external
conditions or as the effect of heredity. And if, further, it can be
proved that the one requires protection more than the other, and that in
several cases it is that one which mimics the protected species, while
the one that least requires protection never does so, it will afford
very strong corroborative evidence that there is a real connexion
between the necessity for protection and the phenomenon of mimicry. Now
the sexes of insects offer us a test of the nature here indicated, and
appear to furnish one of the most conclusive arguments in favour of the
theory that the phenomena termed "mimicry" are produced by natural
selection.

The comparative importance of the sexes varies much in different classes
of animals. In the higher vertebrates, where the number of young
produced at a birth is small and the same individuals breed many years
in succession, the preservation of both sexes is almost equally
important. In all the numerous cases in which the male protects the
female and her offspring, or helps to supply them with food, his
importance in the economy of nature is proportionately increased,
though it is never perhaps quite equal to that of the female. In
insects the case is very different; they pair but once in their lives,
and the prolonged existence of the male is in most cases quite
unnecessary for the continuance of the race. The female, however, must
continue to exist long enough to deposit her eggs in a place adapted for
the development and growth of the progeny