i68 COLOUR IN NATURE chap. 



of the cuticle as in the body, or may be simple inter- 

 ference colours like those of the wings. 



In the large order of beetles (Coleoptera) many 

 varieties of coloration are displayed, some species 

 being notably dull while others exhibit a brilliance 

 rivalling that of the Lepidoptera. Black and deep 

 brown pigments are very common, especially in the 

 elytra or wing-covers, which are of course the con- 

 spicuous features in most beetles. We have already 

 noticed the relation between the thickened cuticle in 

 this region and the pigment. The colour may be 

 simply a dull, dead black as in many Carabidae, or it 

 may be a vivid metallic green or blue as in the rose 

 beetle ; between the two there are many intermediate 

 stages ; but the metallic tints, which are of course 

 optical, are very common. Then there may be 

 patterns and markings in brown and black, as in 

 the very beautiful Macropus longimanus which is 

 elaborately marked with shades of pink and gray. 

 Finally, we find the development of bright red, orange, 

 and yellow (lipochrome, Krukenberg) pigments, as 

 in species of Coccinella and Chrysomela, producing 

 patterns and markings when blended with black 

 and brown. As a whole, however, probably optical 

 colours are most common in beetles. A consider- 

 able number of beetles are furnished with scales, but 

 these are of less importance in coloration than in the 

 Lepidoptera. 



Among the pigments of beetles few have been 

 investigated, but as to the minute details of colouring 

 there are some facts of interest. Thus in Luciola 

 italica, the Italian glow-insect, as described by Emery, 

 the male has the prothorax coloured a clear red, while 



