FLIGHT OF PLANTS AND ANIMALS. 439 



and there a solitary individual whirled by fierce blasts down 

 the mountain-slopes, while, a few hundred feet above, the but- 

 terflies swarm in great numbers. Every passage of the sun 

 from behind a cloud brings them out in scores, and they may 

 often be captured as fast as they can be properly secured. The 

 contrast between the occasional and unwilling visitor in the 

 sub-Alpine region and the swarms which flutter about the 

 upper plateaus is most significant. Yet the Garices, the food- 

 plant of the caterpillar, are quite as abundant in the lower 

 regions as in the upper, even to the species G. rigida, upon 

 which I found the larva feeding. Now, this butterfly [CEneis 

 semidea) belongs to a genus which is peculiar to Alpine and 

 arctic regions ; in fact, it is the only genus of butterflies which 

 is exclusively confined to them. It has numerous members, 

 both in this country and in the Old World. One is confined 

 to the Alps of Europe ; most of the European species, however, 

 are found only in the extreme north. The genus extends 

 across the whole continent of America, and several of its spe- 

 cies occur on the highest elevations of the Rocky Mountains. 

 Several species are common to Europe and America, and it is 

 to one of these that CEneis semidea is most closely allied. A 

 few species descend into the Hudsonian fauna, but, as a whole, 

 the genus has its metropolis farther north. So that, in ascend- 

 ing Mount Washington, we pass, as it were, from New Hamp- 

 shire to northern Labrador ; on leaving the forests, we come 

 first upon animals recalling those of the northern shores of the 

 Gulf of St. Lawrence and the coast of Labrador opposite New- 

 foundland ; and, when we have attained the summit, we find 

 insects which represent the fauna of Atlantic Labrador and the 

 southern extremity of Greenland.* 



Commenting upon these and similar facts connected with 

 other species of butterflies and with several species of moths, 

 Mr. A. R. Grote pertinently says : f 



The question comes up with regard to the White Mountain 

 butterfly, as to the manner in which this species of CEneis 



* "Geology of New Hampshire," vol. i, pp. 340, 341. 

 f "American Journal of Science/' vol. ex, 1S75, pp. 337, 



