VIII 
THE COLOURS OF INSECTS IN GENERAL 
171 
As to function, Mayer has no suggestion to offer, 
but is of opinion that the pigment is undoubtedly 
intrinsic and not derived. Krukenberg believed that 
it functions as a reserve, basing his opinion especially 
on the ground that the large amount present in the 
female is inexplicable on any other hypothesis, and 
that it is of glucoside nature. It may be pointed 
out, however, that chitin itself is a derivative of 
a carbohydrate, and often occurs in considerable 
quantity, and yet no one has suggested that it is 
a reserve product. It seems as yet impossible to 
decide the question of the function of carmine, but 
we may note that as we have already seen in the 
case of Luciola , the association of pigment with the 
cells of the fatty body is not unknown among other 
insects. Mayer describes colourless, crystallised 
bodies in the cells containing carmine, but does not 
discuss their nature ; they may of course again be 
urates. If so the contrast between the pigmentation 
of the sexes in Luciola and Coccus is striking in the 
extreme. 
As to the other pigments of the Hemiptera, Sorby 
investigated those of Aphides, and described a pig¬ 
ment found in them as respiratory, but, according to 
Krukenberg, his results were due to an admixture of 
carmine and lipochromes. The remaining pigments 
do not appear to have been much investigated ; the 
characters of the bright red one found in various 
forms would be of great interest in a comparative 
study of insect pigments. The red pigment of 
Pyrrhocoris apterus is, according to C. Phisalix, closely 
related to carotin, and therefore a lipochrome. 
Among other orders of insects the HYMENOPTERA 
