250 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
Poulton has shown that the reddish fluid voided by the Vanessas 
immediately after emergence from the chrysalis 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 uric 
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 family, the 
pigments in the two cases are chemically quite distinct. This is well 
seen in the genera Leptalis (Pieridae) and Mechanitis (Danaidae). 
In addition to this, Griffiths (’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 empyrical formula C n H 1() Az„ 
N 8 o 10 . 
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 haeino- 
lympli, of the pupa, and that the haemolymph is a proteid substance 
containing egg-albumen, globulin, fibrin, xanthophyll, orthophos- 
phoric acid, iron, potassium, and sodium. 
III. Development of the various Colors in the Pupal 
Wings. 
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 resunffi of 
the principal facts which have been already ascertained. 
(1) Historical Account of previous Researches. 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- 
