Contributions to the theory of natural selection. A series of essays ... By Alfred Russel Wallace ...

RESEMBLANCES AMONG ANIMALS. 113
while its companion of sober brown was looked upon
as the female.' I discovered, however, that the reverse
is the case, and that the rich and glossy colours of
the female are imitative and protective, since they
cause her exactly to resemble the common Euploea
midamus of the same regions, a species which has
been already mentioned in this essay as mimicked
by another butterfly, Papilio paradoxa. I have since
named this interesting species Diadema anomala (see
the Transactions of the Entomological Society, 1869,
p. 285). In this case, and in that of Diadema misippus,
there is no difference in the habits of the two sexes,
which fly in similar localities; so that the influence
of " external conditions" cannot be invoked here as
it has been in the case of the South American Pieris
pyrrha and allies, where the white males frequent
open sunny places, while the Heliconia-like females
haunt the shades of the forest.
We may impute to the same general cause (the
greater need of protection for the female, owing to
her weaker flight, greater exposure to attack, and
supreme importance) —the fact of the colours of female
insects being so very generally duller and less conspicuous than those of the other sex. And that it is
chiefly due to this cause rather than to what Mr.
Darwin terms " sexual selection" appears to be
shown by the otherwise inexplicable fact, that in the
groups which have a protection of any kind independent of concealment, sexual differences of colour
are either quite wanting or slightly developed. The
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