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 Lnciola 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 
Lnciola 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 Libyssa 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 
