soon perceive their mistake, and the one ant soothes the other. (58. P.
Huber, Recherches sur les Moeurs des Fourmis, 1810, pp. 150, 165.)
In this Order slight differences in colour, according to sex, are
common, but conspicuous differences are rare except in the family of
Bees; yet both sexes of certain groups are so brilliantly coloured for
instance in Chrysis, in which vermilion and metallic greens
prevail that we are tempted to attribute the result to sexual
selection. In the Ichneumonidae, according to Mr. Walsh (59.
Proceedings of the Entomological Society of Philadelphia, 1866, pp.
238, 239.), the males are almost universally lighter-coloured than the
females. On the other hand, in the Tenthredinidae the males are
generally darker than the females. In the Siricidae the sexes
frequently differ; thus the male of Sirex juvencus is banded with
orange, whilst the female is dark purple; but it is difficult to say
which sex is the more ornamented. In Tremex columbae the female is much
brighter coloured than the male. I am informed by Mr. F. Smith, that
the male ants of several species are black, the females being
testaceous.
In the family of Bees, especially in the solitary species, as I hear
from the same entomologist, the sexes often differ in colour. The males
are generally the brighter, and in Bombus as well as in Apathus, much
more variable in colour than the females. In Anthophora retusa the male
is of a rich fulvous-brown, whilst the female is quite black: so are
the females of several species of Xylocopa, the males being bright
yellow. On the other hand the females of some species, as of Andraena
fulva, are much brighter coloured than the males. Such differences in
colour can hardly be accounted for by the males being defenceless and
thus requiring protection, whilst the females are well defended by
their stings. H. Muller (60. Anwendung der Darwinschen Lehre auf
Bienen, Verh. d. n. V. Jahrg. xxix.), who has particularly attended to
the habits of bees, attributes these differences in colour in chief
part to sexual selection. That bees have a keen perception of colour is
certain. He says that the males search eagerly and fight for the
possession of the females; and he accounts through such contests for
the mandibles of the males being in certain species larger than those
of the females. In some cases the males are far more numerous than the
females, either early in the season, or at all times and places, or
locally; whereas the females in other cases are apparently in excess.
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