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 (IZ. 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 (JL. 
aconomus) 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 (MI. roylet). 
Other Species. 
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. 
pea 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 
