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Show 3!J2 SEXUAL SELECTION. PART ID. as we can judge, either for protection or as an attraction between the sexes. With many species of butterflies the upper surfaces of the wings are obscurely coloured, and this in all probability leads to their escaping observation and danger. But butterflies when at rest would be particularly liable to be attacked by their enemies ; and almost all the kinds when resting raise their wings vertically over their backs, so that the lowe? sides alone are exposed to view. Hence it is this side which in many cases is obviously coloured so as to imitate the surfaces on which these insects commonly rest. Dr. Rossler, I believe, first noticed the similarity of the closed wings of certain V anessro and other butterflies to the bark of trees. Many analogous and striking facts could be given. The most interesting one is that recorded by Mr. Wallace 5 of a common Indian and Sumatran butterfly (Kallima), which disappears like magic when it settles in a bush; for it hides its head and antennro between its closed wings, and these ia form, colour, and veining cannot be distinguished from a withered leaf together with the footsta]k. In some other cases the lower surfaces of the wings are brilliantly coloured, and yet are protective; thus in Thecla rubi the wings when closed are of an emerald green andresemble the young leaves of the bramble, on which this butterfly in the spring may often be seen seated. Although the obscure tints of the upper or unde1~ surface of many butterflies no doubt serve to conceal them, yet we cannot possibly extend this view to the brilliant and conspicuous colours of many kinds) such as our admiral and peacock V anessro, our white 5 Sec the interesting article in the ' Westminster Review,' July, 18G7, p. 10. A woodcut of the Kallima is given by 1\ir. Wallace in' Huruwicke's 'Scieucc Gossip,' Sept. 1867, p. 196. , CIIAJ>. XI. BUTTEIU<'LIES AND 1\IOTHS. 3D3 cabbage-butterflies (Pieris), or tlJe great swallow-tail Papilio which haunts the open fens-for these butterflies are thus rendered visible to every living creature. vVith these species ·both sexes are alike ; but in the common brimstone butterfly (Gonepteryx rhamni), the male is of an intense yellow, whilst the female is much paler; and in the orange-tip (Anthocharis cardamines) the males alone have the bright orange tips to thei1· wings. In these cases the males and females are equally conspicuous, and it is not credible that thei1· difference in colour stands in any relation to ordinary protection. Nevertheless it is possible that the conspicuous colours of many species may be in an indirect manner beneficial, as will hereafter be explained, by leading their enemies at once to recognise them as unpalatable. Even in this case it does not certainly follow that their bdght colours and beautiful patterns were acquired for this special purpose. In some other remarkable cases, beauty has been gained for the sake of protection, through the imitation of other beautiful species, which inhabit the same district and enjoy an immunity from attack by being in some way offensive to their enemies. The female of our orange-tip buttterfly, above refened to, and of an American species (Anth. genutia) probably shew us, as Mr. vValsh has remarked to me,. the primordial colours of the parent- species of the genus; for both sexes of four or five widely-distributed species are coloured in nearly the same manner. We may infer here, as in several previous cases, that it is the males of Anth. cardamines and genutia which have departed from the usual type of colouring of their genus. In the Anth. sa1·a from California, the orange-tips have become partially developed in the female; for her wings a~·e tipped with reddish-orange, but paler than in the |