XXIII. 



WHERE DID THE BUTTERFLBES COMMON TO THE 

 OLD AND THE NEW WORLD ORIGINATE? 



If we bear in mind the continuity of land be- 

 tween South America and North America, we shall 

 not be surprised at finding, at least along the bor- 

 ders, some butterflies which are found on both con- 

 tinents ; but considering what wide oceans separate 

 on either side the Old World and the New, and 

 that their points of contiguity are in extreme north- 

 ern latitudes, we might expect a greater absence 

 of Old World forms in North America. Yet if we 

 separate from the bulk of butterflies of this conti- 

 nent those which are found south of the Canadian 

 border and east of the Rocky Mountains, we shall 

 find, out of the somewhat less than two hundred 

 and fifty species occurring therein, not over a dozen 

 which may be fairly considered identical with but- 

 terflies found in the Old World, whether in Europe 

 or in Asia. The identity of some of these, many 

 writers have questioned ; about some there is no 



