398 
SEXUAL SELECTION. 
Part IL 
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 14 observes that they 
resemble butterflies in some of their movements ; “ for 
“ instance, in the gentle weaving up and down of the 
“ wings, as if for display, which is more characteristic 
u 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 
Saturnia Jo, is described as having its fore-wings deep 
yellow, 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 1 Proc. Ent. Soc. of London,’ July 6, 1868, p. xxvii. 
15 Harris, 4 Treatise,’ &c., edited by Flint, 1862, p. 395. 
16 For instance, I observe in my son’s cabinet that the males are 
darker tlian the females in the Lasiocampa quercus , Odonestis potatoria , 
Hypogymna dispar , Dasychira pudibunda , and Cycnia mendica. 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. 
