134 RODENTS. 



The list of species of voles being almost endless, space only per- 

 mits of passing references 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 con- 

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

 ceconomus) of Siberia and Kamschatka, 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 

 Himalaya, 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 northwards to the North Cape, 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 

 regard to size and coloration in the Norwegian lemming. Usually, however, its 

 length is about 5 inches ; while the general colour of the fur is yellowish brown, 

 darker above than below, more or less spotted and streaked with blackish 

 brown. ^ 



Lemmings are the most abundant rodents found in Norway, and 

 they have always attracted great interest from the circumstance, 

 that at certain intervals countless swarms descend from the mountains to the cul- 

 tivated plains, and thence make their way, apparently under the influence of some 

 blind impetus, to the sea, into the waters of which they boldly plunge to meet a 

 death by drowning. In the course of such migrations, the lemmings take a straight 

 line across country, swimming rivers or lakes, climbing mountains, and eating their 

 way through fields of corn or grass, and thus leaving a track of desolation in their 

 rear. The line of march is marked by flights of predaceous birds hovering above 

 the hosts ; the flanks and rear of the army being harassed by four-footed foes, who, 

 however, at first make but little apparent diminution in its numbers. Disease also 

 claims its victims ; and from these combined attacks, the numbers which eventually 

 reach the sea, sometimes after an interval of from one to three years from the time 

 of starting, form but a small minority of the original swarm. 



In general appearance, lemmings look not unlike small marmots or hamsters ; 

 and they resemble the latter to a considerable extent in their mode of life. Although 

 in Finmark they occur at the sea-level, in the more southern parts of Scandinavia 

 they are found only high up in the mountains above the level of firs, in the belt 



