vrii 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 G. Phisalix, closely 

 related to carotin, and therefore a lipochrome. 



Among other orders of insects the Hymenoptera 



