$12 The Descent of Man. Part 11. 



surfaces of the wings are brilliantly coloured, and yet are 

 protective ; thus in Thecla rubi the wings wnen closed are of an 

 emerald green, and resemble the young leaves of the bramble, 

 on which in spring this butterfly may often be seen seated. It is 

 also remarkable that in very many species in which the sexes 

 differ greatly in colour on their upper surface, the lower surface 

 is closely similar or identical in both sexes, and serves as a 

 protection. 8 



Although the obscure tints both of the upper and under 

 sides of many butterflies no doubt serve to conceal them, yet we 

 cannot extend this view to the brilliant and conspicuous colours 

 on the upper surface of such species as our admiral and peacock 

 Vanessa?, our white cabbage-butterflies (Pieris), or the great 

 swallow-tail Papilio which haunts the open fens — for these 

 butterflies are thus rendered visible to every living creature. 

 In these species both sexes are alike ; but in the common brim- 

 stone butterfly (Gonepteryx rhamni), the male is of an intense 

 yellow, whilst the female is much paler; and in the orange- 

 tip (ArdhocLaris cardamines) the males alone have their wings 

 tipped with bright orange. Both the males and females in 

 these cases are conspicuous, and it is not credible that their 

 difference in colour should stand in any relation to ordinary 

 protection. Prof. Weismann remarks, 9 that the female of one ol 

 the Lycsense expands her brown wings when she settles on 

 the ground, and is then almost invisible ; the male, on the other 

 hand, as if aware of the danger incurred from the bright blue of 

 the upper surface of his wings, rests with them closed ; and this 

 shews that the blue colour cannot be in any way protective. 

 Nevertheless, it is probable that conspicuous colours are in- 

 directly beneficial to many species, as a warning that they are 

 unpalatable. For in certain other cases, beauty has been gained 

 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 ; but then we have to 

 account for the beauty of the imitated species. 



As Mr. Walsh has remarked to me, the females of our orange- 

 tip butterfly, above referred to, and of an American species 

 (Anth. genutia) probably shew us 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. As in several previous cases, we may here infer that 

 it is the males of Antli. cardamines and yenutia which have 

 departed from the usual type of the genus. In the Antli. sara 



8 Mr. G. Fraser, in ' Nature,' 9 ' Einfluss der Isolirung auf lie 



April 1S71, p. 489. Artbildung,' 1872, p. 58. 



