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 alluded to the well-known noise made by the Death s Head
Sphinx, for it is generally heard soon after the moth has emerged from
its cocoon.
Giard has always observed that the musky odour, which is emitted by two
species of Sphinx moths, is peculiar to the males (4. Zoological
Record, 1869, p. 347.); and in the higher classes we shall meet with
many instances of the males alone being odoriferous.
Every one must have admired the extreme beauty of many butterflies and
of some moths; and it may be asked, are their colours and diversified
patterns the result of the direct action of the physical conditions to
which these insects have been exposed, without any benefit being thus
derived? Or have successive variations been accumulated and determined
as a protection, or for some unknown purpose, or that one sex may be
attractive to the other? And, again, what is the meaning of the colours
being widely different in the males and females of certain species, and
alike in the two sexes of other species of the same genus? Before
attempting to answer these questions a body of facts must be given.
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