This principle does not appear to have been in any way foreseen by
Darwin, although he draws special attention to several elements of
pattern which would now be interpreted by many naturalists as epismes.
He believed that the markings in question interfered with the cryptic
effect, and came to the conclusion that, even when common to both sexes,
they "are the result of sexual selection primarily applied to the male."
("Descent of Man", page 544.) The most familiar of all recognition
characters was carefully explained by him, although here too explained
as an ornamental feature now equally transmitted to both sexes: "The
hare on her form is a familiar instance of concealment through colour;
yet this principle partly fails in a closely-allied species, the rabbit,
for when running to its burrow, it is made conspicuous to the sportsman,
and no doubt to all beasts of prey, by its upturned white tail."
("Descent of Man", page 542.)
The analogous episematic use of the bright colours of flowers to attract
insects for effecting cross-fertilisation and of fruits to attract
vertebrates for effecting dispersal is very clearly explained in the
"Origin". (Edition 1872, page 161. For a good example of Darwin's
caution in dealing with exceptions see the allusion to brightly coloured
fruit in "More Letters", II. page 348.)
It is not, at this point, necessary to treat sematic characters at
any greater length. They will form the subject of a large part of
the following section, where the models of Batesian (Pseudaposematic)
mimicry are considered as well as the Mullerian (Synaposematic)
combinations of Warning Colours.