27 S THE STUDY OF INSECTS 



(i) The blue-eyed grayling, Cercyonis alope alope. — The upper sur- 

 face of the wings is dark brown ; on the outer half of the fore wings there 

 is a distinct yellow band, which extends from vein R5 to the anal vein; 

 in this band there are two dark spots with a white or bluish center. The 

 hind wings usually bear a small spot in cell Cui, which is narrowly 

 rimmed with yellow and has a minute white pupil. The lower surface 

 of the hind wings is either with or without eye-like spots, usually with 

 six of them. 



(2) The dull-eyed grayling, Cercyonis alope nepkele. — In this form 

 the yellow band of the fore wings is either absent or represented by a faint 

 pallid cloud. In other respects it closely resembles the blue-eyed grayling. 



This is a northern form; the southern limits of its range overlap the 

 northern limits of the range of the blue-eyed grayling as given above. 



The White Mountain butterfly, QLneis semidea. — The genus CEneis 

 is composed of cold-loving arctic species whose natural habitat is the 

 far North; but some members of this genus are found within the limits 

 of the United States. Their presence here and their distribution are 

 extremely interesting. The best-known of these forms is the White 

 Mountain butterfly. 



This butterfly is found only on the higher parts (above 5,000 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 colo- 

 nized 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. 



The White Mountain butterfly is a delicate-winged species. The 

 upper surface of the wings is grayish-brown, without spots, except some- 

 times a minute one in cell Mi of the fore wings; the fringe of the wings is 

 brownish-white interrupted with blackish-brown at the ends of the veins. 

 On the hind wings the marbling of the lower surface shows through some- 

 what. On the lower surface, the tip of the fore wings and the greater 

 part of the hind wings are beautifully marbled with blackish-brown and 

 grayish -white. The expanse of the wings is about 1 \ inches. 



THE HELICONIANS 



This subfamily consists chiefly of tropical butterflies. They are of 

 medium or rather large size, and are easily recognized by their narrow 

 and elongated fore wings, which are usually more than twice as long as 

 broad. Most of the species are striking in appearance, being black 

 banded with yellow or crimson, and sometimes with blue. The discal 

 cell of the hind wings is closed by a well-preserved vein. The following 

 species is the only one found in our fauna that unquestionably belongs to 

 this subfamily. 



The zebra, Heliconius charitonius. — This is a black butterfly with its 

 wings banded with lemon yellow. There are three bands on the fore 



