212 ORIGIN OF BUTTERFLIES 



closely allied, and at the same time frequently 

 dimorphic or even polymorphic. The excess to 

 which variability has extended in this country 

 would therefore seem to indicate this as its older 

 abode. The opposite is probably true of Eugonia, 

 represented in this country by a single species ; 

 this is considered by many as identical with Eu- 

 gonia vau-album of Europe, which has there for its 

 companion many very closely allied species. The 

 Gray-veined White (Pieris oleracea), almost our 

 only native species of Pieris, considered by many 

 as the same as the Green-veined White (Pieris 

 napi) of the Old World, has also many allies in 

 the Old World, and therefore, like Pieris rapae, 

 probably originated there. Finally, Pamphila, 

 represented in this country by only a single species, 

 the Arctic Skipper (P. mandan), widely separated 

 from all its allies, strong of flight and extending to 

 Alaska, belongs to a genus represented in the Old 

 World with its immediate allies by several peculiar 

 types, which range across the entire breadth of the 

 continent ; we must therefore look upon this spe- 

 cies as one introduced from the Old World, but at 

 a period of time so long ago as to have become 

 fairly distinct from the primal stock. 



If now we turn our attention to the butterflies 



