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The Descent of Man and Selection in Relation to Sex

Insects, continued.
Courtship of butterflies--Battles--Ticking noise--Colours common to both sexes, or more
brilliant in the males--Examples--Not due to the direct action of the conditions of life--
Colours adapted for protection--Colours of moths--Display--Perceptive powers of the
Lepidoptera--Variability-- Causes of the difference in colour between the males and
females--Mimicry, female butterflies more brilliantly coloured than the males--Bright
colours of caterpillars--Summary and concluding remarks on the secondary sexual
characters of insects--Birds and insects compared.
In this great Order the most interesting points for us are the differences in colour between
the sexes of the same species, and between the distinct species of the same genus. Nearly
the whole of the following chapter will be devoted to this subject; but I will first make a
few remarks on one or two other points. Several males may often be seen pursuing and
crowding round the same female. Their courtship appears to be a prolonged affair, for I
have frequently watched one or more males pirouetting round a female until I was tired,
without seeing the end of the courtship. Mr. A.G. Butler also informs me that he has
several times watched a male courting a female for a full quarter of an hour; but she
pertinaciously refused him, and at last settled on the ground and closed her wings, so as
to escape from his addresses.
Although butterflies are weak and fragile creatures, they are pugnacious, and an emperor
butterfly (1. Apatura Iris: 'The Entomologist's Weekly Intelligence,' 1859, p. 139. For the
Bornean Butterflies, see C. Collingwood, 'Rambles of a Naturalist,' 1868, p. 183.) has
been captured with the tips of its wings broken from a conflict with another male. Mr.
Collingwood, in speaking of the frequent battles between the butterflies of Borneo, says,
"They whirl round each other with the greatest rapidity, and appear to be incited by the
greatest ferocity."
The Ageronia feronia makes a noise like that produced by a toothed wheel passing under
a spring catch, and which can be heard at the distance of several yards: I noticed this
sound at Rio de Janeiro, only when two of these butterflies were chasing each other in an
irregular course, so that it is probably made during the courtship of the sexes. (2. See my
'Journal of Researches,' 1845, p. 33. Mr. Doubleday has detected ('Proc. Ent. Soc.' March
3, 1845, p. 123) a peculiar membranous sac at the base of the front wings, which is
probably connected with the production of the sound. For the case of Thecophora, see
'Zoological Record,' 1869, p. 401. For Mr. Buchanan White's observations, the Scottish
Naturalist, July 1872, p. 214.)
Some moths also produce sounds; for instance, the males Theocophora fovea. On two
occasions Mr. F. Buchanan White (3. 'The Scottish Naturalist,' July 1872, p. 213.) heard a
sharp quick noise made by the male of Hylophila prasinana, and which he believes to be
produced, as in Cicada, by an elastic membrane, furnished with a muscle. He quotes,
also, Guenee, that Setina produces a sound like the ticking of a watch, apparently by the
aid of "two large tympaniform vesicles, situated in the pectoral region"; and these "are
much more developed in the male than in the female." Hence the sound-producing organs
in the Lepidoptera appear to stand in some relation with the sexual functions. I have not