Page:Descent of Man 1875.djvu/329

 from California, the orange-tips to the wings have been partially developed in the female; but they are paler than in the male, and slightly different in some other respects. In an allied Indian form, the Iphias glaucippe, the orange-tips are fully developed in both sexes. In this Iphias, as pointed out to me by Mr. A. Butler, the under surface of the wings marvellously resembles a pale-coloured leaf; and in our English orange-tip, the under surface resembles the flower-head of the wild parsley, on which the butterfly often rests at night. The same reason which compels us to believe that the lower surfaces have here been coloured for the sake of protection, leads us to deny that the wings have been tipped with bright orange for the same purpose, especially when this character is confined to the males.

Most Moths rest motionless during the whole or greater part of the day with their wings depressed; and the whole upper surface is often shaded and coloured in an admirable manner, as Mr. Wallace has remarked, for escaping detection. The front-wings of the Bombycidæ and Noctuidæ, when at rest, generally overlap and conceal the hind-wings; so that the latter might be brightly coloured without much risk; and they are in fact often thus coloured. During flight, moths would often be able to escape from their enemies; nevertheless, as the hind-wings are then fully exposed to view, their bright colours must generally have been acquired at some little risk. But the following fact shews how cautious we ought to be in drawing conclusions on this head. The common Yellow Under-wings (Triphæna) often fly about during the day or early evening, and are then conspicuous from the colour of their hind-wings. It would naturally be thought that this would be a source of danger; but Mr. J. Jenner Weir believes that it actually serves them as a means of escape, for birds strike at these brightly coloured and fragile surfaces, instead of at the body. For instance, Mr. Weir turned into his aviary a vigorous specimen of Triphæna pronuba, which was instantly pursued by a robin; but the bird's attention being caught by the coloured wings, the moth was not captured until after about fifty attempts, and small portions of the wings were repeatedly broken off. He tried the same experiment, in the open air, with a swallow and T. fimbria; but the large size of this moth probably interfered with its capture. We are thus reminded of a statement made