272 DARWINISM chap. 



A hundred other cases might be c[uoted in which the 

 female is either more obscurely coloured than the male, or 

 gains protection by imitating some inedible species ; and any 

 one Avho has watched these female insects flying slowly 

 along in search of the plants on which to deposit their 

 eggs, will understand how important it must be to them 

 not to attract the attention of insect -eating birds by too 

 conspicuous colours. The numljer of birds which capture 

 insects on the mng is much greater in tropical regions 

 than in Europe ; and this is perhaps the reason Avhy many 

 of our showy species are alike, or almost alike, in both 

 sexes, while they are protectively coloiu^ed on the under side 

 which is exposed to view Avhen they are at rest. Such are 

 our peacock, tortoise-shell, and red admiral butterflies ; while 

 in the tropics we more commonly find that the females are 

 less conspicuous on the upper surface even when protectively 

 coloured beneath. 



We may here remark, that the cases already quoted prove 

 clearly that either male or female may be modified in colour 

 apart from the opposite sex. In Pieris pyrrha and its allies 

 the male retains the usual type of coloration of the whole 

 genus, while the female has acquired a distinct and peculiar 

 style of colouring. In Adolias dirtea, on the other hand, 

 the female appears to retain something like the primitive 

 colour and markings of the tAvo sexes, modified perhaps for 

 more perfect protection ; while the male has acquired more and 

 more intense and brilliant colours, only sho"vving his original 

 markings by the few small yellow spots that remain near the 

 base of the wings. In the more gaily coloured Pieridos, of 

 which our orange-tip butterfly may be taken as a type, we see in 

 the female the plain ancestral colours of the group, while the 

 male has acquired the brilliant orange tip to its wings, prob- 

 ably as a recognition mark. 



In those species in which the under surface is protectively 

 coloured, we often find the upper surface alike in both sexes, 

 the tint of colour being usually more intense in the male. But 

 in some cases this leads to the female being more consjHcuous, 

 as in some of the Lycsenidce, where the female is bright blue 

 and the male of a blue so much deeper and soberer in tint as 

 to appear the less brilliantly coloui-ed of the two. 



f1 



