13 



find any principle, teleological or otherwise, which will help us to 

 get at the meaning of the facts presented to our observation ? The 

 answer in this case is very much like that given to the former 

 enquiry. There is a residue of facts which we cannot at present 

 explain ; but in many instances we are able, with a high degree of 

 probability, to assign a definite reason, founded on utility, for the 

 difierent aspects assumed by the male and female respectively. In 

 order to get some further light upon this, let us examine the matter 

 a little more closely. 



It is probably well known to most of my hearers that of the 



three kinds of common white butterfly that haunt our lanes and 



gardens throughout the summer, some individuals are furnished 



with black spots on the upper surface of the wings, and some not. 



Speaking generally, the heavily spotted individuals are females, and 



those with few or no spots are males. So far then, as this particular 



group of butterflies is concerned, the females tend to exhibit a larger 



amount of dark pigment than the males. If we take into view not 



only the white butterflies of our own country but also those of other 



regions, we find the same tendency often carried to a higher pitch. 



There is a genus of w^hite butterflies, named Belenois, some species 



of which are not unlike our common whites, though there is 



generally somewhat more black about them than in our native kinds. 



These J>ele)wis butterflies belong mostly to Africa, but they are 



also found in southern Asia, and south-eastwards as far as the 



Australian continent and some of the Pacific islands. The females 



in nearly every instance show a strong accentuation of the dark 



markings of the males. This may go on to such a degree that the 



female might almost be called a "black" butterfly instead of a 



white one. In some females of Belenois severina from the shores of 



the Victoria Nyanza, the white of the upper surface is reduced to a 



dusky basal patch on each of the four wings, next to the body, the 



remainder of the wing-surface being of a smoky black. The cor- 



respondmg male has a black apex and border ; but these are spotted 



with white, and occupy far less space than the dark areas of the 



female. So too, the male of Belenois peristhene, one of the Pacific 



island forms, has a deep black apical patch and marginal band ; but 



in the female the apical and marginal black have overspread 



perhaps two-thirds of the whole wing-space. Good examples of the 



same state of things may be seen in the genus Delias. The male of 



Delias descoiiibesi, from the Eastern Himalayas and the Indo-Chinese 



peumsula, is on the upper surface a white butterfly with a narrow 



fuscous edging. On tiae corresponding surface in the female the 



forewings are black with some white spots and streaks, and the 



hindwings, though mainly white, have a broad black margin. In 



Delias inferna from New Guinea, the male is orange coloured with 



black apex and border ; the female is black with an area of dusky 



orange at the bases of the wings, occupying perhaps a third of the 



whole surface. Many species of the genus Teracolns are character- 



