TNSECTS. 





peared. The presence of this immense ice-sheet, of course, had its influence 

 on the climate, and thus on the animals and plants. When the glacier had 

 its greatest southern extent, arctic forms dwelt along its border ; and when 



the sheet retreated, these species followed it. 



An illustration of this is afforded by the distribu- 

 tion of the White Mountain butterfly and its allii 

 This form belongs to the genus Chionobas, which 

 represented in the United States east of the Mis- 

 sissippi River, only on two or three of the highi 

 peaks of the White Mountains. The nearest points 

 where the same genus is found are Labrador and Colo- 

 rado. It is supposed, to account for this peculiarity in 



Fig. 281. — White Moun- .... 



tain butterriy (CMono- {\ ie distribution (which is paralleled b\ some plant-. 



bas semidea) . . . » 



that the White Mountain colony is composed of strag- 

 glers left behind on the re- ^ 

 treat of the glacier, and that 

 only on these elevated peaks 

 did they find a temperature 

 and a climate adapted to 

 their needs. On any other 

 hypothesis their distribution 

 is inexplicable. 



The genus Morpho (again 

 no common name) is one of 

 the beauties of the tropics, 

 and. strange to say, its mem- 

 bers are limited to South 

 America and the islands of 

 the eastern seas, none being 

 found between. The expla- 

 nation of this is difficult ; for 

 here it is not possible to 

 invoke the aid of glaciers in 

 explanation. There are some 

 thirty-five species known, 

 those of the East present- 

 ing some marked differences 

 from those of Brazil. In the latter country most of the 

 metallic blue above, shading off into black, while the under s 

 the wings is a rich brown, ornamented with eye-like spo 

 them are very large, measuring seven inches across the outspread wi 



Fig. 282. — Neoptolemus butterfly I Morpho 



