The Descent of Man

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