186 THE FUNDAMENTAL ASPECT OF COLORATION 



butterfly, Colias philodice, in which the usual yellow-green 

 coloration was replaced by blue-green. He concluded that some 

 factor was involved which caused the yellow components of 

 chlorophyll to become broken down or decolorised. By acting 

 locally from the nuclei of the cells of the intestinal epithelium it 

 changed the crude chlorophyll during its absorption into the blood. 

 The result has been that a pigment derived from the blue-green 

 component of chlorophyll, viz., chlorophyll a, is left intact and 

 becomes the persisting colouring material. The eggs of imagines 

 derived from blue-green caterpillars were pure alabaster-white, 

 not the normal cream-white, an effect due to the absence of 

 yellow pigment in the blood of the parent. The pupa is only 

 slightly less blue-green than the larva ; the exuviae are white 

 instead of the normal yellow. The wing colours of the adult, being 

 due to uric acid derivatives, are not affected, but the eye colour is 

 of a bluish-green rather than the normal apple green. A further 

 point of great interest is that the cocoon colour of its parasite, 

 Apanteles flaviconchce, is white instead of the usual yellow, and it 

 thus appears that the lack of yellow pigment in the host affects 

 the colour of the salivary secretion of its parasite. Gerould's work 

 suggests, in the light of Poulton's observations, that the blue- 

 green coloration in C philodice is derived from the clover upon 

 which the larva feeds, but actual proof by way of chemical or 

 spectroscopic examination remains to be established. 



Przibram (1913) has contested the existence of chlorophyll in 

 insects, and has classified under the non-committal name of 

 " Tiergrun " a variety of green animal pigments. Spectroscopic 

 examination alone he claims is insufficient to establish their 

 identity, and chemical methods are necessary. An ether solution 

 of the green pigment in grasshoppers and Cantharis, when heated 

 with an equal quantity of alcohol solution of potassium hydroxide, 

 yields a yellow precipitate and the solution becomes clear. An 

 extract of plant pigment, on the other hand, remains green and 

 turbid. Other striking differences appear upon heating and 

 adding more of the hydroxide, while concentrated sulphuric 

 acid, when added to the ether solution, and also nitric acid, give 

 very different reactions when compared with their effects upon 



