COLOR IN MOTHS AND BUTTERFLIES. 159 



facture various colors from the haemolymph by means of 

 chemical reagents. Also if the color so manufactured be simi- 

 lar to some color upon the mature wing, it may be expected to 

 present reactions to chemical reagents similar to those of the 

 color on the wing. As far as my experiments go I find this to 

 be the case. For example, if one treat the haemolymph of 

 Samia cecropia with warm concentrated HNO3, it congeals 

 into a deep chrome-yellow mass. If, now, ammonia be added 

 to excess, it changes to a reddish-orange, which is very similar 

 in color to the reddish-orange band that crosses the upper surface 

 of the hind wings of the moth. Now this reddish-orange band of 

 the moth is changed to chrome-yellow by HCl or HNO3, and 

 then if ammonia be added, the original color reappears. Exactly 

 the same sequence of reactions is produced with the reddish- 

 orange pigment derived from the haemolymph. A number of 

 other tests of this nature were tried, and all gave confirma- 

 tory results. The details of these tests may be found in the 

 author's ('96) paper on the development of wing-scales and 

 their color. 



In 1864 Landois observed that when the blood of insects is 

 allowed to dry in the air it is very apt to assume a color which 

 is similar to the ground-color of the wings of the mature insect 

 from which the blood is drawn. It is well known that the 

 most universal colors of the more lowly organized moths are 

 the drab-gray and yellow-drab tints, and these colors may be 

 derived from their haemolymphs by mere exposure to the air. 

 The brilliant reds, yellows, etc., are the result of more or less 

 complex chemical processes, which have been slowly effected, 

 probably through the agency of natural selection. It is inter- 

 esting to notice that Hopkins finds that the white pigment 

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

 and red pigments of the same butterflies are due to the deriva- 

 tives of uric acid. Also Griffiths ('92) has shown that the green 

 pigment of several species of butterflies is due to a complex 

 derivative of uric acid. Indeed, the haemolymph of the pupa 

 is itself very complex, and it seems probable that various 

 substances, some of them highly colored, might be derived 

 from it by chemical processes. In the Saturnidae, for example. 



