270 DARWINISM chap. 



is smaller and much less protectively formed and coloured. 

 In the bees and wasps (Hymenoptera) it is also the rule that 

 the sexes are alike in colour, though there are several cases 

 among solitary bees where they differ; the female being 

 black, and the male brown in Anthophora retusa, while in 

 Andrsena fulva the female is more brightly coloured than the 

 male. Of the great order of beetles (Coleoptera) the same 

 thing may be said. Though often so rich and varied in their 

 colours the sexes are usually alike, and Mr. Darwin was only 

 able to find about a dozen cases in which there was any con- 

 spicuous difference between them. 1 They exhibit, however, 

 numerous sexual characters, in the length of the antennae, and 

 in horns, legs, or jaws remarkably enlarged or curiously modi- 

 fied in the male sex. 



It is in the family of dragonflies (order Neuroptera) that 

 we first meet with numerous cases of distinctive sexual 

 coloration. In some of the Agrionidse the males have the 

 bodies rich blue and the wings black, while the females have 

 the bodies green and the wings transparent. In the North 

 American genus Hetserina the males alone have a carmine 

 spot at the base of each wing ; but in some other genera the 

 sexes hardly differ at all. 



The great order of Lepidoptera, including the butterflies and 

 moths, affords us the most numerous and striking examples of 

 diversity of sexual colouring. Among the moths the differ- 

 ence is usually but slight, being manifested in a greater inten- 

 sity of the colour of the smaller winged male ; but in a few 

 cases there is a decided difference, as in the ghost -moth 

 (Hepialus humuli), in which the male is pure white, while the 

 female is yellow with darker markings. This may be a 

 recognition colour, enabling the female more readily to discover 

 her mate ; and this view receives some support from the fact 

 that in the Shetland Islands the male is almost as yellow as 

 the female, since it has been suggested that at midsummer, 

 when this moth appears, there is in that high latitude sufficient 

 twilight all night to render any special coloration unneces- 

 sary. 2 



Butterflies present us with a wonderful amount of sexual 



1 Darwin's Descent of Man, p. 294, and footnote. 

 2 Nature, 1871, p. 489. 





