3 H The Descent of Man. Tart I J. 



by Mr. "Wallace/ 3 namely, that in the Brazilian forests and 

 Malayan islands, many common and highly-decorated butterflies 

 are weak flyers, though furnished with a broad expanse of wing ; 

 and they " are often captured with pierced and broken wings, 

 " as if they had been seized by birds, from which they had 

 " escaped : if the wings had been much smaller in proportion 

 " to the body, it seems probable that the insect would more 

 " frequently have been struck or pierced in a vital part, and 

 * thus the increased expanse of the wings may have been in- 

 " directly beneficial." 



Display. — The bright colours of many butterflies and of some 

 moths are specially arranged for display, so that they may be 

 readily seen. During the night colours are not visible, and 

 there can be no doubt that the nocturnal moths, taken as a 

 body, are much less gaily decorated than butterflies, all of 

 which are diurnal in their habits. But the moths of certain 

 families, such as the Zygsenidee, several Sphingidae, Uraniidae 

 some Arctiidse and Saturniidse, fly about during the day or 

 early evening, and many of these are extremely beautiful, being 

 far brighter coloured than the strictly nocturnal kinds. A 

 few exceptional cases, however, of bright-coloured nocturnal 

 species have been recorded. 14 



There is evidence of another kind in regard to display. 

 Butterflies, as before remarked, elevate their wings when at 

 rest, but whilst basking in the sunshine often alternately raise 

 and depress them, thus exposing both surfaces to full view ; and 

 although the lower surface is often coloured in an obscure 

 manner as a protection, yet in many species it is as highly 

 decorated as the upper surface, and sometimes in a very 

 different manner. In some tropical species the lower surface is 

 even more brilliantly coloured than the upper. 15 In the Eng- 

 lish fritillaries (Argynnis) the lower surface alone is orna- 

 mented with shining silver. Nevertheless, as a general rule, 

 the upper surface, which is probably more fully exposed, is 

 coloured more brightly and diversely than the lower. Hence 

 the lower surface generally affords to entomologists the more 



13 'Westminster Review,' July Insects of New England,' 1842, p. 315. 

 1867, p. 16. 15 Such differences between the 



14 For instance, Lithosia ; but upper and lower surfaces of the 

 Prof. Westwood (' Modem Class, of wings of several species of Papilio, 

 Insects,' vol. ii. p. 390) =eems sur- may be seen in the beautiful plates 

 prised at this case. On the relative to Mr. Wallace's ' Memoir on the 

 colours of diurnal and nocturnal Papilionidae of the Malayan Region,' 

 Lepidoptera, see ibid. pp. 333 and in 'Transact. Linn. Soc.' vol. xxv 

 392 ; also Harris, ' Treatise on the part i. 1865. 



