The Descent of Man and Selection in Relation to Sex, Vol. IDarwin, Charles
Science
The Descent of Man and Selection in Relation to Sex, Vol. I
Darwin, Charles
Evolution (Biology); Human beings -- Origin; Sex differences; Sexual dimorphism (Animals); Sexual selection in animals
character of the offspring.
Female Lepidoptera require, as Mr. Wallace insists, some days to
deposit their fertilised ova and to search for a proper place; during
this period (whilst the life of the male was of no importance) the
brighter-coloured females would be exposed to danger and would be liable
to be destroyed. The duller-coloured females on the other hand would
survive, and thus would influence, it might be thought, in a marked
manner the character of the species,—either of both sexes or of one
sex, according to which form of inheritance prevailed. But it must not
be forgotten that the males emerge from the cocoon-state some days
before the females, and during this period, whilst the unborn females
were safe, the brighter-coloured males would be exposed to danger; so
that ultimately both sexes would probably be exposed during a nearly
equal length of time to danger, and the elimination of conspicuous
colours would not be much more effective in the one than the other sex.
It is a more important consideration that female Lepidoptera, as Mr.
Wallace remarks, and as is known to every collector, are generally
slower flyers than the males. Consequently the latter, if exposed to
greater danger from being conspicuously coloured, might be able to
escape from their enemies, whilst the similarly-coloured females would
be destroyed; and thus the females would have the most influence in
modifying the colour of their progeny.
There is one other consideration: bright colours, as far as sexual
selection is concerned, are commonly of no service to the females; so
that if the latter varied in brightness, and the variations were
sexually limited in their transmission, it would depend on mere chance
whether the females had their bright colours increased; and this would
tend throughout the Order to diminish the number of species with
brightly-coloured females in comparison with the species having
brightly-coloured males. On the other hand, as bright colours are
supposed to be highly serviceable to the males in their love-struggles,
the brighter males (as we shall see in the chapter on Birds) although
exposed to rather greater danger, would on an average procreate a
greater number of offspring than the duller males. In this case, if the
variations were limited in their transmission to the male sex, the males
alone would be rendered more brilliantly coloured; but if the variations
were not thus limited, the preservation and augmentation of such
variations would depend on whether more evil was caused to the species
by the females being rendered conspicuous, than good to the males by
certain individuals being successful over their rivals.
Public-domain text, read in full here on John Shaqi.
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