Flying squirrels range over the forested parts of North America from Guatemala to Alaska and northern Canada and from the Atlantic to the Pacific. A closely related genus (_Pteromys_) occurs in Europe. Two species are found in North America. The small _volans_ ranges in eastern United States, Mexico, and Guatemala, while the larger _sabrinus_ occurs in parts of the western United States, most of Canada, and central Alaska. Near the Great Lakes the two species occur in the same area, probably in different habitats. Howell (1918: 16) recognized 18 subspecies of _sabrinus_, five of which were recorded in the state of Washington. One of these (_olympicus_) proves to be a synonym of an earlier-named subspecies but another form (_bangsi_), not recorded for Washington by Howell, has been found in the Blue Mountains in the southeastern corner of the state (Taylor and Shaw, 1929: 18). Flying squirrels are strictly arboreal and occur only in woods and forests. They prefer areas where trees grow close together and to considerable heights. Older woods with dead stubs and hollow trees are preferred. They occasionally invade attics of cabins and other habitations of man. The old Forestry Building on the University of Washington Campus, later the home of the Washington State Museum, was inhabited by flying squirrels for many years. Several specimens preserved in the Museum prove the poor judgment of the animal in choosing a natural history museum as a home. Relatively little is known of the detailed habits of _Glaucomys sabrinus_ although the life history of the eastern _Glaucomys volans_ has been described. Flying squirrels are active all winter, even in the high mountains. They are often caught in traps set for fur bearers and, where trapping is an important means of livelihood, they are serious pests. Flying squirrels do not actually fly but only glide through the air. The loose fold of fur between their limbs is stretched by extending the legs. With it the flying squirrel is able to sail 50 yards or more. The flat tail serves as a rudder and allows the squirrel to change direction while in flight. Glides end with an upward swoop, allowing the squirrel to alight, head upwards, on a tree trunk slightly lower than their starting point.