INTRODUCTION, XXI 



to form pigments and other secondary sexual characters. Perhaps 

 no insect will make this clearer than the purely dimorphic Epione 

 parallelaria (vespertaria). The female is lethargic, has a large abdomen 

 and produces a large supply of eggs, the wings are small and pale 

 yellow in colour. The male is active, has a slender body, with large 

 ample wings of a rich orange colour with purple borders. The larvge 

 of the males and females are of about equal size, the male excels in 

 wing membrane and richly developed pigment, the female excels in 

 the size of the abdomen. Is it not evident that the surplus matter in 

 the male is utilised here in a given direction ? Fidonia atomaria 

 presents in the South of England a parallel case, the female large-bodied, 

 with small wings of a whitish ground colour ; the male slender-bodied, 

 with ample wings of a rich ochreous-brown, sometimes almost orange 

 in colour. In localities where their food is sparse, as on some of the 

 Scotch moors, the males have no such active surplusage and closely 

 resemble the females, the dimorphism being but little marked. There 

 is of course a double action here, as the $ rests on the top of the 

 heather, the female hiding nearer the ground, the latter being, also, more 

 sluggish and retiring. The colour of the $ accords better with the 

 heather foliage, that of the ? with the stones and undergrowth, but 

 however much this " natural selection " and " heredity " will account for 

 the intensification of a protective coloration, it will not explain its 

 origin, which is, I believe, purely physiological. Endromis versicolor, 

 Bombyx quercus, Angerona prunaria, Chilo phragmitellus are instances 

 amongst very many others, in which the female is larger (owing to 

 heavy body) but has much paler pigment than the male. But a paler 

 pigment does not always mean a less highly developed one, although 

 probably it does so in the cases just quoted, in fact, some striking 

 instances of pale colours richly pigmented occur to me, e.g., Bombyx 

 neustria (yellow males) ; B. castrensis, in which the male is more 

 richly pigmented and better scaled, and even brighter in general 

 appearance although paler in coloration than the female, but such 

 cases hardly appear to affect the general question, as they belong 

 essentially to the same class as those previously mentioned in Class 1. 

 I look on " bright coloring or rich pigmenting " as " a natural ex- 

 pression of the male constitution " only so far as the fact that a 

 male larva well-fed, compared with a female larva equally well-fed 

 will have a surplus of material which is utilised in the development 

 of certain tendencies, present ab ovo in the organism, and which 

 tendencies, well developed, become secondary sexual characters. 



The influence of " sexual selection " in producing the brilliancy of 

 male coloring, is admitted as a minor factor by Geddes and Thompson 

 and so also is the " natural selection " of Wallace, and there is no doubt 

 that both are factors, the former indirectly, and more, however, 

 generally as the result of chance than through any selective faculty 

 possessed by the female, although occasionally as in H. kutmdi, 

 selection probably takes place ; the latter more directly and actively 

 as the result of every-day conditions tending to the survival of the 

 fittest, by the protection of those females which are sober-coloured and 

 unattractive, which are passed over by their enemies, and which 

 therefore stamp their character more certainly on each successive 

 brood by heredity. But the real basis must be sought for in the 



