144 COLOUR IN NATURE chap. 



considerable evidence to show that yellow, green, 

 and brown ground-colours in vegetarian larvae are 

 all due to pigments derived from the food. The 

 pigments frequently colour the blood very markedly ; 

 it will be recollected that the blood in insects has 

 probably no connection with respiration, but is 

 hsemolymph, primarily concerned with nutrition. 

 The blood of the pupse and adults is often likewise 

 green and coloured with these derived pigments, 

 but as yet there seems to be no instance described 

 in butterflies or moths in which these pigments 

 assist in coloration (a possible exception will be 

 discussed when we consider butterflies). They are 

 retained within the body, however, and not in- 

 frequently colour the eggs and thus the newly- 

 hatched larvae. The break between larval and 

 adult coloration seems in Lepidoptera to be complete. 

 But lipochrome pigments at least are not always 

 absent in adult insects, for Zopf describes red and 

 yellow pigments belonging to this group in several 

 small leaf-eating beetles. In Linapopuli, for example, 

 which lives on the leaves of the poplar, a red 

 lipochrome colours the wing-covers and part of the 

 abdomen, it is found in the secretion of the salivary (?) 

 glands, and occurs associated with oil-drops in the 

 ova. One is tempted to suppose that its presence 

 here is associated with the prolongation of the larval 

 diet into adult life. 



Meaning of Derived Pigments 



We must now proceed to consider what the 

 abundant occurrence of derived pigments in insects 



