_Description._--Though it is similar in general characters and proportions to the long-tailed weasel, the ermine is much smaller and has a relatively shorter tail. It is darker and less reddish or yellowish in summer. Adult males measure about 10 inches in length, of which 3-1/2 inches is the length of the tail. Females measure about 8 inches and have tails 2 inches long. The upper parts are chocolate brown; the underparts are white or pale yellow. Along the coast of Washington, the pale color of the underparts is more restricted in the ermine than in the long-tailed weasel. The dark brown tail has a black tip. Ermines east of the summit of the Cascades become pure white in winter, save for the black tail tip. West of the summit of the Cascades the winter pelt is similar to the summer pelt but is slightly paler with denser underfur. Ermines in America range from the Arctic southward, in mountainous areas, to the southern end of the Sierra Nevada in California, and in the Rocky Mountains to northern New Mexico. In Washington they are found over the entire state except the arid parts of eastern Washington, where only the long-tailed weasel occurs. So far as my observations go, the ermine is principally nocturnal in Washington; I have seen only one abroad in the daytime. It dashed from a roadside thicket near Glacier, Whatcom County, and was crushed beneath the wheels of a car. Taylor and Shaw (1927: 53) note several instances of diurnal activity of the ermines at Mount Rainier National Park. The ermine seems to feed principally upon mice. Its small size adapts it to entering burrows that larger weasels cannot enter. It probably eats chipmunks, birds, and other small, warm-blooded animals. Ermines climb readily and are often taken in traps set in trees for martens. Near Skykomish, King County, William Hoffman took two ermines in traps set in burrows of mountain beavers. The mountain beavers were needed for use as bait on his trap line. The traps were reset and later caught mountain beavers. Seemingly the ermines were traveling through the burrows, perhaps to catch the mice which utilize the burrows as highways, rather than to prey upon mountain beavers. It is difficult to see how the tiny ermine could kill an adult mountain beaver, which outweighs it many times. Should the incisors of the mountain beaver close even once upon an ermine it would most certainly be seriously wounded or killed. Judging by the forest habitat occupied by the ermine in Washington, one might expect its principal food to consist of deer mice (_Peromyscus maniculatus_), red-backed mice (_Clethrionomys_) and meadow mice (_Microtus_).