chap, vii THE'COLOURS OF THE LEPIDOPTERA 139 
aspect of the colours, and even now little is known 
of their meaning to the organism in which they 
occur. 
We do not propose here to consider in detail the 
characters of the colours of insects in their relations 
to the habits of the species. The subject has been 
most fully worked out for the Lepidoptera, and the 
facts of the case, as well as the conclusions drawn, 
will be found in Mr. Poulton’s Colours of Animals 
and Mr. Wallace’s Darwinism. Here we are con¬ 
cerned more with the proximate origin of colour 
than with its ultimate justification. 
The colours of insects are of especial importance 
to the comparative physiologist on account of the 
general tendency of the group to exhibit a life-history 
divided into two sharply-contrasted stages: the 
larval stage in which growth and nutrition are at 
their maximum, and an adult stage in which these 
are almost at a standstill, while the activities are 
directed to the maintenance of the species . 1 
As might be expected the colours of the two 
stages are often very sharply contrasted. In the 
majority of cases the colours of the larval stage tend 
to be sober as compared with the often bright colours 
of the adult, just as generally speaking the larva 
may be called sedentary as compared with the active 
imago. Further, since the cuticle of the larva is 
usually little differentiated as compared with that of 
the adult, and we have already considered the relation 
existing between a differentiated cuticle and the 
1 For an exceedingly interesting discussion of this and other points 
connected with the physiology of insects, the reader should consult 
Dr. David Sharp’s “ Insects” in the Cambridge Natural History. 
