THE ENTOMOLOGIST 



Vol. XXVIIL] JANUAEY, 1895. [No. 880. 



THE PIGMENTS OF THE PIERID.E : A CONTRIBUTION TO 

 THE STUDY OF EXCRETORY SUBSTANCES WHICH 

 FUNCTION IN ORNAMENT.- 



By F, Gowland Hopkins, 



Demonstrator of Physiology and Chemistry at Guy's Hospital, London. 



The paper deals with the chemistry of the wing pigments of 

 that group of butterflies known as the Pieridse, and demonstrates 

 the excretory nature of these pigments. The following are tlie 

 salient facts dealt with, most of the statements being based on 

 original observations described in the paper: — 



1. The wing scales of the white Pieridae are shown to contain 

 uric acid, this substance bearing the same relation to the scale 

 as do the pigments in the coloured Pieridse, and therefore 

 functioning practically as a white pigment. 



2. The yellow pigment which is so widely distributed in the 

 Pieridse (being found in the majority of the genera) is shown to 

 be a derivative of uric acid. 



3. The properties of this yellow pigment are described, and 

 the results of its analysis are given. The pigments of various 

 yellow-coloured genera are shown to be identical. 



4. It is shown that this yellow pigment may be artificially 

 produced by heating uric acid with water in sealed tubes at high 

 temperatures. The product so obtained was originally described 

 by Hlasiwetz as " mycomelic acid"; but evidence is brought 

 forward to show that the substance described and analysed by 

 this chemist was in reality urate of ammonium coloured by a 

 yellow body, probably identical with the natural pigment. 



5. The identity of the natural and artificial products is 

 demonstrated by the fact that both yield under like treatment a 

 purple derivative, which has a well-marked and easily identified 

 absorption spectrum. 



* Abstract of a Paper read before the Boyal Society. 



ENTOM. — JAN. 1895. B 



