246 DIGONEUTISM 



and in half a dozen or more of these we find quite 

 similar disparities, all of which are in the same 

 direction. 



The European Tortoise-shell (Aglais urticae), 

 for example, is generally double brooded ; occa- 

 sionally a triple brood is mentioned ; it is one of 

 the commonest of European butterflies, and reaches 

 from the North Cape to the Mediterranean ; our 

 congeneric species, the American Tortoise-shell 

 (Aglais milberti), is rarely found south of the 

 northernmost parts of the United States, and yet 

 it is triple brooded in all parts of Canada. Even 

 the Dappled Fritillary (Brenthis montinus) of the 

 White Mountains is probably double brooded, 

 while all the mountain species of Europe are 

 single brooded. Everes amyntas, again, occurs 

 throughout Europe, with the exception of certain 

 northern and northwestern portions, and is double 

 brooded; our Tailed Blue (Everes comyntes), 

 named for the resemblance to its European con- 

 gener, and by some careless authors considered 

 identical with it, is also a widespread insect ; but 

 even in New England, which is at the northern 

 limit of its eastern range, it is triple brooded. 

 The widespread European Blues, Kusticus argTis 

 and R. aegon, the Silver-studded Blue, are usually 



