VIII THE COLOURS OF INSECTS IN GENERAL 173 



especially coloration by lipochromes. When, how- 

 ever,, the adults, as in the beetles, are remarkable for 

 the great development of the cuticle, the coloration 

 may be due either to the presence of a large amount 

 of dark pigment or to structural colours. Coloration 

 by waste products has not yet been described outside 

 the Lepidoptera, at least in detail. 



General Aspects of Insect Coloration 



It is impossible to conclude this section on the 

 colours of insects without touching, be it never so 

 slightly, on some of the interesting questions which 

 cluster around the subject. As most of the current 

 theories of colour have been in large part founded on 

 insects, it is not surprising that the literature of the 

 subject has already reached enormous dimensions, so 

 that to attempt to abstract even the more important 

 papers would be impossible. We have therefore 

 confined our attention very closely to the physio- 

 logical side, and the result is of course professedly 

 incomplete. Many of the omitted subjects, such as 

 the colours of the sexes, the relation between food 

 and colour, variable coloration, and so on, are, how- 

 ever, already in their rough outlines familiar to most 

 people, and their physiological side has been so little 

 investigated, that little more can be profitably said. 

 There are, however, one or two points which, on 

 account of their general interest, are worthy of more 

 extended treatment. 



