THE LEMMINGS 1305 



vole (M. rutilus}, which inhabits the circumpolar regions of both Hemispheres; their 

 differences in coloration being merely such as might well be due to the varying 

 climatic conditions of the countries they severally inhabit. 



The Alpine vole (M. nivalis), which is the last species to which 

 we refer at any length, is interesting on account of the elevated 

 regions forming its habitat. It is a small species with a relatively-long tail; the 

 total length being about seven inches, of which slightly more than half is taken up 

 by the tail. The ears are large, and the number of prisms in the first upper molar 

 tooth is the same as in the water vole. The color varies from brownish gray above 

 and grayish white beneath to pure white. This species has an exceedingly-limited 

 distribution, being confined to the Alps and Pyrenees, where it ranges from an 

 elevation of about four thousand feet to the limits of perpetual snow. It is, indeed, 

 most abundant near the snow line, above which it also sometimes wanders in search 

 of the scanty vegetation which exists at such altitudes. Not only is the Alpine 

 vole found in these dreary regions during the short season when the ground is more 

 or less free from snow, but it likewise remains there from year's end to year's end. 

 Accordingly, for upward of nine or ten months of the year, it lives beneath a deep 

 pall of snow. Here it makes regular runs, along which it travels in search of food 

 when the supply hoarded for winter use becomes exhausted. No other known 

 Mammal leads a similar existence. 



The list of species of voles being almost endless, space only permits 

 Other Species ~ c . . ,. . A _ __ ^, 



or passing reterences to a few of the more interesting. In North 



America the commonest species is the meadow vole (M. riparius), which in the 

 northern regions during the winter abandons its frozen burrows and forms nests on 

 the surface of the ground, which soon become buried in the snow. The heat of the 

 little animal inside melts and cakes the surrounding snow, which thus forms a 

 continually-increasing dome-shaped mass around the nest. The root vole ( M. cecono- 

 mus) of Siberia and Kamchatka, is interesting on account of the large stores of food 

 it accumulates in its burrows, and likewise on account of its migratory habits, which 

 resemble those of the lemming. Numerous voles occur in the Himalayas, Tibet, 

 and Central Asia; the earliest described Himalayan species being Royle's vole 

 (M. roylei). 



THE LEMMINGS 

 Genus Myodes 



Closely related to the voles are the lemmings, of which one species, commonly 

 known as the Norwegian lemming {Myodes lemmus) , inhabits the mountains of the 

 Scandinavian Peninsula and thence northward to Cape North, while the second 

 is confined to North America. Lemmings are distinguished from voles by their 

 heavier build, more convex and obtusely-snouted head, extremely-short tail and by 

 the soles of the small feet being covered with hair. They have also longer claws, 

 thicker fur, and very small ears; while there are likewise important differences in 

 the structure of the skull and teeth. There is considerable individual variation in 



