Lasionycteris noctivagans [Allen], U. S. Nat. Mus. Bull., 43:105, March 14, 1894.
Type.—None designated; described from a specimen obtained in the "eastern United States."
Measurements.—Five males from San Juan County, Washington, average: total length 96.2; length of tail 46.4; hind foot 8.5; ear 16; height of tragus 7.2; weight 8.2 grams.
Distribution.—Forested areas of the entire state. This species is migratory and first appears about the middle of May. September 15th is the latest recorded occurrence, when one was seen at Seattle, King County. Marginal records are: Sportsmans Lake (W. W. D.), in the northwest; Carson ([Taylor] and [Shaw], 1929: 9) in the southwest; Pass Creek Pass (W. W. D.) in the northeast; and Bly ([Taylor] and [Shaw], 1929: 9) in the southeast.
Remarks.—The chocolate-brown color phase of the silver-haired bat is most common east of the Cascade Mountains, while almost all specimens from western Washington represent the black phase.
This medium-sized bat is the darkest-colored species living in the state, ranging from chocolate-brown to nearly black. Numerous white-tipped hairs give the upper parts a frosted appearance. The upper surface of the interfemoral membrane is well furred, a character shared only with Lasiurus. The dental formula (i. 2-2/3-3, c. 1-1/1-1, p. 2-2/3-3, m. 3-3/3-3 = 36) is the same as that of Corynorhinus. The small ears and short tragus immediately distinguish the silver-haired bat from the long-eared bat.
The genus Lasionycteris contains but a single species, of which no geographic races have been described. It ranges across North America from coast to coast and from central Canada southward, in forested areas, nearly to Mexico. This species is known to be migratory, and southern records probably do not represent breeding individuals.
In Washington these bats have been taken in the Transition, Canadian, and Hudsonian life-zones. They were found near clearings in forests of open pine woods in the arid section of eastern Washington, near mountain hemlock thickets in the high mountains, and in the dense rain-forests of the Pacific Coastal area.
