ButteiHies of the Mountain Summits. 



89 



pattern of a 'northern form by the refrigeration, during de- 

 velopment, of a southern form, is something readily distin- 

 guishable from a mere general darkening of color tone. 



To return from our digression to the interesting Chionobas 

 butterflies, whose distribution was excuse for it, we find them 

 represented on the peaks of the Sierra Nevada by at least one 

 well-recognized species, Chionobas ivallda, with the probability 

 that one or two other species, so far recorded only from the 

 Rocky Mountains, or from the Coast Mountains of British 

 America, will be found in California. Chionobas is larger than 

 Erebia, and is of a wood-brown color, with one or two small 

 blackish eye-spots in the apex of each fore wing. It is, even 

 more strictly than Erebia, a thing of the bare rocks of the 

 mountain's summit. It is rarely seen upon flowers or sipping 

 water from a snow-bank's edge. It alights on the rough rocks, 

 balancing itself in the harsh wind, with many a tipping and 

 righting, but ever clinging fast with delicate legs and tiny 

 claws. Or it settles with curious, hesitant, then suddenly cer- 

 tain manner on the little lee patch of bare soil made by the 

 weathering of some great rock. The wings seem curiously 

 large for the frail body, and there is something in all its ap- 

 pearance that makes it different from lowland butterflies, just 

 as its strange life as hermit on the bleak peaks is so pro- 

 foundly different from all that we conceive the Hfe of the gre- 

 garious, dancing, painted flutterers of the flower-strewn valley 

 meadows to be. 



Scudder, who studied Chionobas semidea on the top of Mt. 

 Washington, notes his surprise upon discovering that these but- 

 terflies, which one would expect, perhaps, to find endowed with 

 powerful flight to resist the fierce blasts that sweep across their 

 summit home, are really unusually weak as flyers. They can 

 offer no resistance to the winds, he says, and if they ascend 

 more than two or three feet above the surface of the ground, 

 or pass the shelter of some projecting ledge of rocks, they are 

 hurled headlong to immense distances until they can again hug 

 the earth. He remarks, with interest, their special devices to 

 escape pursuit. One is, when alarmed, indeed at most times, 

 to fly up and down the slopes, rarely along them, thus render- 

 ing pursuit particularly difficult. But it seems hard to accept 



