172 
COLOUR IN NATURE 
CHAP. 
and Diptera may be mentioned as exhibiting a 
striking parallelism of coloration. In various instances 
(e.g. Volucella , Eristalis, etc.) this has of course been 
described as protective mimicry on the part of the 
flies, but it is difficult to look at collections of the 
two orders side by side without being struck by the 
similarities of colouring. In both cases the body is 
frequently covered with hairs which are important 
factors in coloration, but the hair may be completely 
absent and the surface may be then brilliantly 
metallic or black and polished-looking. Among 
pigmental colours in both cases black, dull brown, 
and yellow are the commonest. There seem to be 
no investigations on the pigments in either case. 
Contrast between Coloration of Lepi- 
DOPTERA AND OTHER INSECTS 
In comparing the colours of other insects with 
those of the Lepidoptera, we have to notice that in 
the former the occurrence of much beauty or special¬ 
isation of colour in the larvae is relatively rare. The 
larvae not infrequently are of the form popularly 
known as maggots or grubs, and they are usually 
colourless or almost so. Similarly, outside the 
Lepidoptera, it is not very common to find the 
nutritive and reproductive stages sharply contrasted 
in large groups, many of the adults being not in¬ 
frequently both. Directly associated with this fact, 
or as the indirect result of the diminished specialisa¬ 
tion which makes food-taking possible to the adults, 
we find that the adults may display that type of 
coloration which is larval for the Lepidoptera, that is 
