146 THE OLDEST BUTTERFLY 



most conspicuous instances which we have, we 

 would recall the two butterflies before referred to, 

 as now found exclusively upon the barren summits 

 of the White Mountains, and at no other point in 

 or near New England. 



The most striking feature in their occurrence is 

 the fact that the genera into which these two but- 

 terflies fall have an altogether special interest of 

 great significance in this connection ; for they are 

 exclusively or very largely arctic, and there are 

 but three other such genera known in the whole 

 butterfly world. These others are Erebia, of 

 which there are some examples in subarctic Amer- 

 ica and in the Rocky Mountains ; Agriades, which 

 hardly comes nearer to us than Labrador, and is 

 found again in the high mountains of the western 

 half of our continent ; and Eurymus, which is less 

 exclusively arctic than the others, having represent- 

 atives also over almost the entire globe, excepting 

 in tropical countries, and of which we have three 

 species in New England, one of them subarctic. 

 Oeneis, the genus to which one of our Mt. Wash- 

 ington forms belongs, occurs elsewhere only in 

 high mountain regions, and, with but one or two 

 exceptions, beyond forest limits, whether toward 

 the pole or the zenith. Several species occur 



