The Descent of Man

which the characters follow our two rules in
their order of development.
As most insects emerge from the pupal state in
a mature condition, it is doubtful whether the
period of development can determine the transference
of their characters to one or to both
sexes. But we do not know that the coloured
scales, for instance, in two species of butterflies,
in one of which the sexes differ in colour,
whilst in the other they are alike, are developed
at the same relative age in the cocoon. Nor do
we know whether all the scales are simultaneously
developed on the wings of the same
species of butterfly, in which certain coloured
marks are confined to one sex, whilst others are
common to both sexes. A difference of this kind
in the period of development is not so improbable
as it may at first appear; for with the Orthoptera,
which assume their adult state, not by
a single metamorphosis, but by a succession of
moults, the young males of some species at first