OF ARTS AND SCIENCES. 151 



These are all cases of melanism, and may be taken as examples of a 

 class; in the first two, perhaps iu all, it is only toward the southern 

 part of the insect's range that the melanism appears, and is in accord- 

 ance with the general rule that melanic antigeny is more common at 

 the south, while its opposite, albinism, is more frequent toward the 

 north. 



Albinism, for instance, is a common feature in the northern genus 

 Enrynms. In our common E. Philodice (God.) and E. Earytheme 

 (lioisd.), many females may be found in which the bright yellow or 

 orange of the upper surface is replaced by a sordid greenish-white; 

 and if we go farther north, or to higher altitudes, we shall tiud other 

 species, iu which the albinism has become complete, affecting all the 

 females. 



It is a curious circumstance that, while albinic antigeny finds its 

 most complete expression in high tem[)erate regions, and melanic an- 

 tigeny prevails toward the tropics, the albinic females of a partially 

 antigenic sj^ecies never appear in the spring brood, but increase in 

 numbers throughout the hot season ; while, at least iu the case of the 

 blue butterfly mentioned, the melanic females emerge in early spring, 

 are confined to this biood, and are replaced in warmer weather by the 

 gynandromorphic females ; thus, spring apparition appears to be corre- 

 lated with southern distrIl)ution, and summer apparition WMth northern 

 distribution : these two phenomena appear, in either case, to be directly 

 antagonistic. 



Although both albinism and melanism may become complete, par- 

 tial antigeny, wherever it exists, is confined to the phenomena of 

 melanism and albinism, and does not extend to the more varied forms 

 of complete colorational antigeny, to which reference will now be 

 made. 



In the male of Xanthidla Nicippe (Cram.), the black bordering 

 band of the wings is sharply defined, and extends across the entire 

 outer margin ; in the female, the band is blurred, and stops abruptly 

 before it reaches the lower angle of the front wings, or has half trav- 

 ersed the hind wings. In Redone Brettus (Boisd.-LeC), the female is 

 very dark-brown, almost black, with two little yellow spots in the 

 middle of the front wings ; while the male differs totally, being tawny 

 with indented brown borders and an oblique black dash in the middle 

 of the front wings : at first glance, no one could suppose them iden- 

 tical. In Semnopsyche Diana (Cram.), the male is a rich dark-brown 

 with a very broad fulvous margin upon all the wings, marked on the 

 front wings by one or two rows of black spots. The female, on the 



