264 PROCEEDINGS OF THE AMERICAN ACADEMY 



York, and Micliigan. But the pale variety, H. Nevadensis, occurs 

 where the caterpillar feeds on Spiroea salicifolia in Maine, and proba- 

 bly farther in the west. The Caterpillars are slightly different in 

 color. Actias hma, fed in Europe on the European walnut, is 

 slightly different in color of the wings from those fed in America 

 on the American walnut. The specimens from Texas are more bril- 

 liantly colored than those from New England. I have seen in the 

 Museum in Berlin, Prussia, a large box filled with different varieties 

 of the imago of Bombyx caja, and was told by Professor Klug that a 

 number of them were artificially produced by feeding the omnivorous 

 caterpillar with different kinds of food. The most abnormal variety 

 came from caterpillars fed with crumbs of dry bread. Perhaps simi- 

 larly reliable facts might be found in the literature. Mr. Speyer has 

 given, as related before, some information concerning a different shade 

 of the colors of moths which are found in America as well as in 

 Europe. But there are probably different factors working together 

 to produce these variations. 



Krukenberg,* in his elaborate paper, " Ueber thierische Farbstoffe 

 und deren physiologische Bedeutung," comes to the conclusion that 

 the change of color (in perfectly developed insects) is a consequence 

 of the change of food, and can be explained by the alteration and 

 mutation of the pigments through heat and light. His experiments 

 were made for the purpose of finding the cause of the turning into 

 yellow or red by green grasshoppers in autumn. He tries to answer 

 two questions : First, does the pigment of grasshoppers originate 

 directly out of the food, and does it consist of pure chlorophyll or a 

 substance containing chlorophyll, or is it to be accepted as a peculiar 

 production of the organism ? Second, is the color the consequence of 

 only one pigment, or of several? His detailed answer is as follows : 



"It is evident that the green color of the grasshoppers is the con- 

 sequence of several different pigments, which can be separated by 

 chemical process." 



The immersion of the green grasshopper in ether colors it yellow, 

 and the grasshopper becomes cochineal red. The same is observed 

 when insects are treated with hot water or alcohol. The turning 

 to cochineal red is not the consequence of a chemical mutation of the 

 yellow-green pigment, but solely of its extraction, and the subsequent 



* C. Fr. W. Krukenberg: Vergl. physiolog. Studien an den Kiisten d. 

 Adria, 1880, 1881, vol. ill. p. 62. 



