greyish-ochreous, while the lower surface is magnificently ornamented
by an ocellus of cobalt-blue, placed in the midst of a black mark,
surrounded by orange-yellow, and this by bluish-white. But the habits
of these three moths are unknown; so that no explanation can be given
of their unusual style of colouring. Mr. Trimen also informs me that
the lower surface of the wings in certain other Geometrae (17. See also
an account of the S. American genus Erateina (one of the Geometrae) in
Transactions, Ent. Soc. new series, vol. v. pl. xv. and xvi.) and
quadrifid Noctuae are either more variegated or more brightly-coloured
than the upper surface; but some of these species have the habit of
holding their wings quite erect over their backs, retaining them in
this position for a considerable time, and thus exposing the under
surface to view. Other species, when settled on the ground or herbage,
now and then suddenly and slightly lift up their wings. Hence the lower
surface of the wings being brighter than the upper surface in certain
moths is not so anomalous as it at first appears. The Saturniidae
include some of the most beautiful of all moths, their wings being
decorated, as in our British Emperor moth, with fine ocelli; and Mr.
T.W. Wood (18. Proc Ent. Soc. of London, July 6, 1868, p. xxvii.)
observes that they resemble butterflies in some of their movements;
for instance, in the gentle waving up and down of the wings as if for
display, which is more characteristic of diurnal than of nocturnal
Lepidoptera.
It is a singular fact that no British moths which are brilliantly
coloured, and, as far as I can discover, hardly any foreign species,
differ much in colour according to sex; though this is the case with
many brilliant butterflies. The male, however, of one American moth,
the Saturnia Io, is described as having its fore-wings deep yellow,
curiously marked with purplish-red spots; whilst the wings of the
female are purple-brown, marked with grey lines. (19. Harris,
Treatise, etc., edited by Flint, 1862, p. 395.) The British moths
which differ sexually in colour are all brown, or of various dull
yellow tints, or nearly white. In several species the males are much
darker than the females (20. For instance, I observe in my son s
cabinet that the males are darker than the females in the Lasiocampa
quercus, Odonestis potatoria, Hypogymna dispar, Dasychira pudibunda,
and Cycnia mendica. In this latter species the difference in colour
between the two sexes is strongly marked; and Mr. Wallace informs me
that we here have, as he believes, an instance of protective mimicry
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