The banded lemmings form a strongly marked group, containing a number of species inhabiting circumpolar regions. In North America they occur nearly everywhere in the arctic and subarctic parts, including Greenland, most of northern Canada, including the Arctic islands, and a large part of Alaska, including some of the Aleutian Islands. They range as far northward as vegetation affords them a proper food supply and have been well known to many of the explorers of those stern northern wilds. To the southward they extend into the subarctic northern forests, where they usually keep to the open barren areas. Not much is known of their life histories on this continent. They are mainly nocturnal and live in burrows from two to three feet long, ending with a nest chamber four or five inches in diameter, warmly lined with grass and moss. Near the nest there is usually a branch burrow a foot or more long which is used for sanitary purposes and as a place of refuge when the main burrow is invaded. In the nests during early summer litters generally containing about three young are brought forth. Ordinarily the burrows open in unsheltered places, but in wooded regions may be under a log or beneath a bush or the roots of a tree. No runways lead out from the burrows as is customary with many of their relatives. They are active throughout the winter, making many tunnels along the surface of the ground under the snow, which are revealed when it melts in spring. These surface tunnels are their foraging roads, safe from most of the fierce storms which rage overhead. At times, however, the snowy shelter is blown away or some other cause brings the lemmings to the surface, where they blunder aimlessly about, soon to be captured by some enemy or to perish from the cold. As their infrequent appearance on top of the snow is usually during storms, the Alaskan Eskimos have a legend that these white lemmings live in the land above the stars and descend in a spiral course to the earth during snowstorms. Although banded lemmings never become so extraordinarily numerous over great areas as the brown species, they become very abundant at times in the barren grounds of Canada and the Arctic islands and migrate from one part of their range to another. The best observation in regard to this was made by Rae in June at the mouth of the Coppermine River. On the west bank of the river north of the Arctic Circle he encountered thousands of them speeding northward. The ice on some of the smaller streams had broken up and he was amused to see the little animals running back and forth along the banks looking for a smooth place in the stream, indicating a slow current, where they could swim across. Having found such a place, they at once jumped in and swam quickly to the opposite side, where they climbed out and, after shaking themselves like dogs, continued their journey as though nothing had happened.