176 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY, 



Poulton has shown that the reddish fluid voided by the Vanessas 

 immediately after emergence from the chrysahs contains uric acid, 

 and Hopkins ('94) says that when the yellow Pieridae emerge, they 

 often void from the rectum a large quantity of uric acid. It should 

 be borne in mind however, as Urech himself suggests, that the pig- 

 ment found within the wings may not be identical in chemical com- 

 position with the similarly colored fluid from the alimentary tract. 



Hopkins ('89, '91, '94, '96) has discovered that the white pigment 

 found in the scales of Pieridae is uric acid, and that the red and 

 yellow pigments of the Pieridae are due to derivatives of m-ic 

 acid. He also says, " these uric acid derivatives used in ornamen- 

 tation, are apparently confined to the Pieridae alone among butter- 

 flies." Hence when a Pierid mimics an insect of another famil}^, the 

 pigments in the two cases are chemically quite distinct. This is well 

 seen in the genera Leptalis (Pieridae) and ^Nlechanitis (Danaidae). 



In addition to this, Griftiths ('92) finds that the green pigment 

 found in Papilio, Parthenos, Hesperia, Limenitis, Larentia, Ino, and 

 Halias is a derivative of uric acid, to which he gives the name of 

 "Lepidopteric acid " and assigns the empyi-ical formula C^ H^^ Az.^ 



In a paper published in 1896 in the Bulletin of the Museum of 

 Comparative Zoology at Harvard College, Vol. 29, I have shown, 

 p. 226-230, that the pigments of the scales of Lepidoptera are 

 derived by various chemical processes from the blood, or haemo- 

 lymph, of the pupa, and that the haemolymph is a proteid substance 

 containing egg-albumen, globulin, fil)rin, xanthophyll, orthophos- 

 phoric acid, iron, potassium, and sodium. 



III. Development of the various Coloks iif the Pupal 



WlXGS. 



A few researches have been carried out upon this interesting 

 topic, but as the literature is scattered and has never been brought 

 together, it will perhaps not be amiss to present a brief resume of 

 the principal facts which have been already ascertained. 



(1) Historical Account of jyi'evious Mesearches. In 1889 

 Schaffer ('89) discussed the question of the order and time of 

 appearance of the colors in the pupal wings of several of the 

 Vanessas. Unfortunately he apparently did not make his obser- 



