412 
THE STUDY OF INSECTS. 
The larvae of both of these species feed upon grass; 
the butterflies fly during the latter half of the summer, 
and the larvae begin hibernating as soon as hatched. 
The Hybrid Graylings, Cercyonis alope-nephele .—The 
Dull-eyed Grayling is a northern species, occurring in 
Canada and the northern part of the United States. The 
Blue-eyed Grayling is found throughout the greater part of 
the United States east of the Rocky Mountains, except in 
the extreme North and South. The ranges of the two 
overlap in the southern portions of New England, New 
York, Michigan, Wisconsin, Iowa, and Nebraska; and in the 
northern portions of Illinois, Indiana, and Ohio. In this 
belt both species occur, and also intergrades between them; 
these intergrades may be called Hybrid Graylings. 
The White Mountain Butterfly, (Ends semidea (CE-ne'is 
se-mid'e-a).—Comparatively few students who study this 
book will collect this butterfly; but we refer to it on ac* 
count of its remarkable distribution. It is found only on 
the higher parts (above 5000 feet) of the White Mountains 
in New Hampshire, and on the highest peaks of the Rocky 
Mountains of Colorado, above 12,000 feet. 
These two widely separated colonies of this butterfly are 
believed to be the remnants of an Arctic fauna which was 
forced southward during the Ice Age. At the close of this 
period, as the Arctic animals followed the retreating ice 
northward, the tops of these mountains became colonized 
by the cold-loving forms. Here they found a congenial 
resting place, while the main body of their congeners, which 
occupied the intervening region, was driven northward by 
the increasing heat of the lower land. Here they remain, 
clinging to these islands of cold projecting above the fatal 
sea of warmth that fills the valleys below. 
