208 ORIGIN OF BUTTERFLIES 



sides of Bering Strait, could unquestionably pass 

 from one continent to the other at this point of 

 their nearest approach. In which continent the 

 species originated must be judged rather from the 

 abundance and variety of its nearest allies on the 

 one continent and on the other. In America there 

 is but a single additional species of the genus 

 occurring, and that so rare that I am not aware 

 that more than one specimen has ever been found, 

 occurring as it does in the mountains of Mexico. 

 In the Old World several species occur in southern 

 Asia, but in addition there is a very closely allied 

 genus, Hamadryas, which occurs in Europe but 

 not in America, and it is therefore in the highest 

 degree probable that the origin of the species 

 should be looked for in the Old World. As to 

 the two species of Vanessa, we have shown in our 

 New England Butterflies that the genus is divis- 

 ible into two sections, into one of which cardui 

 falls, into the other atalanta ; and that the imme- 

 diate congeners of cardui are found altogether in 

 the New World and those of atalanta in the Old. 

 The distribution of these species in the New World 

 is more restricted than that of E. antiopa, so that 

 there is no probability of any recent transfer of 

 forms between the two continents, and we are left 



