Jumping mice are boreal mammals occurring in wooded regions ranging from the Arctic region southward to North Carolina, New Mexico and California. Jumping mice are of rather general distribution in Washington, being only locally common. They are partial to damp, boggy areas but avoid true swamps. They occur in clearings in the forests in the Puget Sound area and in meadows in river bottoms and in jungles in ravines. They reach their greatest abundance in the boggy meadows and glacial cirques of the mountains and spread out from such areas to seemingly less favored habitat on dryer slopes and heather meadows. Unlike many species, they do not seem to inhabit talus slides. They are entirely absent from the eastern Washington desert. Sometimes the jumping mouse walks on all four feet but the ordinary means of progression is by short hops on the hind feet alone. When startled they travel in great bounds, covering six feet or more at a jump. When jumping they make considerable noise, swishing or rustling through the grass and landing with an audible thud. The long tail serves as a balancing organ. A specimen whose tail had been lost was reported by Svihla and Svihla (1933: 133) to turn somersaults in the air and invariably to land on its back rather than its feet. Jumping mice become very fat and hibernate in middle summer or early fall. In the lowlands they disappear by late July but in the mountains they remain active until the middle of September. They spend the winter in nests of grass several feet beneath the surface. A hibernating individual figured by Flahaut (1939: 17) was curled in a ball, head down with the tail wrapped completely around the greatest circumference of the ball. Near Seattle the principal food of the jumping mouse was the velvet grass (_Holchus lanatus_), and the seeds of grasses and the broad-leaved dock. The fruit of the blackberry (_Rubus macropetalus_) is eaten and occasional individuals are seen with the chin stained a deep purple from the juice. The new-born young of the jumping mouse were reported by Svihla and Svihla (1933: 132) to average 0.8 grams in weight. They are pink, hairless, lacking even the facial vibrissae, with eyes closed and ears folded. =Zapus princeps trinotatus= Rhoads _Zapus trinotatus_ Rhoads, Proc. Acad. Nat. Sci. Philadelphia, 1894, p. 421, January 15, 1895. _Zapus imperator_ Elliot, Field Columb. Mus. Publ. 30, zoöl. ser., 1:228, February 1, 1899 (type from Sieg's Ranch, Elwha River, Olympic Mountains, Clallam County, Washington). _Type._--Obtained on Lulu Island, mouth of Fraser River, British Columbia, by S. N. Rhoads on May 31, 1892; type in Philadelphia Academy of Natural Sciences. _Racial characters._--Similar to _oregonus_ but brighter; sides orange; underparts creamy white; buffy area often present on chest.