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. 
