l8o ENTOMOLOGY 



Albinism is exceptional whiteness or -paleness of coloration, and is 

 due usually to deficiency of pigment, but in some instances (Pieridae) 

 to the presence of a white pigment. 



The common yellow butterfly, Colias philodice, and its relatives, 

 are frequently albinic. Scudder observed that albinism among butter- 

 flies in America appears to be confined to a few Pieridae, and to be re- 

 stricted to the female sex; is more common in subarctic and subalpine 

 regions than in lower latitudes and altitudes, and only in the former 

 places includes all the females. At low altitudes, however, instead of ap- 

 pearing early in the year as might be expected, the albinic forms appear 

 during the warmer months. 



The experiments made by Gerould on C. philodice show that the 

 number of albinic female offspring from white females crossed with 

 yellow males is in accordance with Mendelian law. Albinism is not 

 entirely confined to the female as Scudder thought, for white males 

 occur, though they are extremely rare. "They may be expected in 

 regions where the white female is especially abundant" (Gerould). 



In Europe there are many albinic species of butterflies, and they 

 are by no means confined to family Pieridae. 



Melanism is unusual blackness or darkness of coloration. As to 

 how it is produced little is known, though warmth is probably the most 

 potent influence, and some attribute it to moisture, as was mentioned. 

 Pictet obtained partial melanism in Vanessa urtic& and V. polychloros 

 by subjecting the larvae to moisture. 



In warm latitudes, some females of our Papilio glaucus are blackish 

 brown with black markings, instead of being, as usual, yellow with 

 black markings. In the South, some males of the spring brood of 

 Cyaniris pseudargiolus are partly or wholly brown instead of blue. 

 A melanic male of Colias philodice occurs as an extremely rare muta- 

 tion. A melanic variety of pomace fly, Drosophila, with a black body, 

 follows the Mendelian law in its appearance in breeding experiments. 



Seasonal Coloration. When butterflies have more than one brood 

 in a year, the broods usually differ in aspect, sometimes so much that 

 their specific identity is revealed only by rearing one brood from 

 another. The same species may exist under two or more distinct 

 forms during the same season in other words, may be seasonally dimor- 

 phic, trimorphic or polymorphic. 



Thus Polygonia interrogations has two forms, fabricii and umbrosa, 

 which differ not only in coloration, but even in the form of the wings 



