398 SEXUAL SELECTION. Part II. 



face in certain moths is not so anomalous a circum- 

 stance as it at first appears. The Saturniidse include 

 some of the most beautiful of all moths, their wings 

 being decorated, as in our British Emperor moth, with 

 fine ocelli ; and Mr. T. W. Wood w 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 but- 

 terflies. The male, however, of one American moth, the 

 Satumia Io, is described as having its fore-wings deep 

 yellow 7 , 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, 



14 ' Proc. Ent. Soc. of London,' July 6, 1868, p. xxvii. 



15 Harris, ' Treatise/ &c, edited by Flint, 1862, p. 395. 



16 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, Dasycliira pudibunda, and Cycnia mendlca. 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 he believes, 

 an instance of protective mimickry 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 are white ; 

 and Mr. Stainton observed that this latter moth was rejected 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. 



