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.^ 



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 



' 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. 



