VIII THE COLOURS OF INSECTS IN GENERAL 169 



that of the female is paler and more yellow. The 

 cuticle is, however, similarly coloured in both sexes, 

 and the difference is due to the different colouring of 

 the fatty bodies in the two. In both these contain 

 concretions of urates, but in the female they are 

 chalk-white, in the male a delicate rose colour. In 

 the related Lampyris, on the other hand, both sexes 

 have rose-coloured concretions. In Luciola the testes 

 are also coloured red by concretions deposited in 

 the connective tissue. The association between the 

 urates and pigment is interesting, but Emery says 

 nothing as to the characters of the pigment. In 

 Luciola the adult does not eat, reproduction being 

 the only object of existence at this stage. It is a 

 point of some interest that we have here an indirect 

 utilisation of the pigment of the fatty body in colora- 

 tion, a condition which suggests a transition towards 

 the complete utilisation of coloured excretory pro- 

 ducts seen in some of the Lepidoptera. 



The Hemiptera display great variety in their 

 coloration, and apparently contain many peculiar 

 pigments. Optical colours are not very common 

 but are far from being unknown ; thus Eurymela 

 shows a faint metallic sheen, and Lihyssa signata is 

 marked by alternate bands of vivid metallic green 

 and black. 



Among pigmental colours we have not only 

 uniformity of colour but also frequently beautiful 

 patterns and markings. Our own familiar Bishops' 

 Mitres {Tropicoris) exhibit considerable beauty of 

 marking, while many of the large Indian and 

 American forms have most beautifully marked and 

 spotted wings. In these cases the fore -wings are 



