COLOUR IN NATURE 
CHAP. 
168 
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 
