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Show 39S SEXUAL SELECTION. PAnT II. face in certain moths is not so anomalous a circumstance as it at first appears. The Saturniidre include some of the most beautiful of all moths, their wings being decorated, as in our British Emperor moth, with fine ocelli; and J\ir. T. W. Wood 14 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, nor as far as I can discover hardly any foreign species, which are brilliantly coloured, 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.15 The British moths which differ sexually in colour are all brown, or various tints of dull yellow, or nearly white. In several species the males are much darker than the females, 16 and these belong to groups which generally fly about during the afternoon. On the other hand, in many genera, as Mr. Stainton informs me,. H 'Proc. Ent. Soc. of London,' July 6, 18G8, p. xxvii. 15 Harris, ' Treatise,' &c., edited by Flint, 18G2, p. 395. 1° 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, Dasychim 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 be believes, an instance of protective mimickl-y confined to one sex, as will hereafter be more fully explained. The white female of the Cycnia resembles the very common Spilosoma menthrasti, both sexes of which arc white; and Mr. Stainton observed that this latter moth was rej ected with utter disgust by a whole brood of young turkeys, which were fond of eating other moths; so that if the Cycnia was commonly mistaken by British birds for the Spilosoma, it would escape being devoured, and its white deceptive colour would thus be highly beneficial. CHAP. XI. BUTTERFLIES AND MOTHS. 399 the males have the hind-wings whiter than those of the female-of which fact Agrotis exclamationis offers a good instance. The males are thus rendered more conspicuous than the females, whilst flying about in the dusk. In the Ghost Moth (Hepialus humuli) the difference is more strongly marked ; the males being white and the females yellow with darker markings. It is difficult to conjecture what the meaning can be of these differences between the sexes in the shades of darkness or lightness; but we can hardly suppose that they are the result of mere variability with sexuallylimited inheritance, independently of any benefit thus derived. From the foregoing statements it is impossible to admit that the brilliant colours of butterflies and of some few moths, have commonly been acquired for the sake of protection. We have seen that their colours and elegant patterns are arranged and exhibited as if for display. Hence I am led to suppose that the females generally prefer, or are most excited by the more brilliant males ; for on any other supposition the males would be ornamented, as far as \re can see, for no purpose. We know that ants and certain 1amellicorn beetles are capable of feeling an attachment for each other, and that ants recognise their fellows after an interval of several months. Hence there is no abstract improbability in the Lepidoptera, which probably stand nearly or quite as high in the scale as these· insects, having sufficient mental capacity to admire bright colours. They certainly discover flowers by colour, and, as I have elsewhere shewn, the plants which are fertilised exclusively by the wind never have a conspicuously-coloured corolla. The Humming-bird Sphinx may often be seen to swoop down from a distance on a bunch of flowers in the midst of green foliage |