One species in California destroys large quantities of raisins drying in the field by carrying them off to some shelter, where they cut out the seeds and leave the rest of the fruit. I have seen half a pound of raisins under a piece of board, the result of the night’s work of a single mouse. While field mice are always destructive, at intervals they have sudden and mysterious accelerations of increase and become so excessively abundant that they are a veritable plague. Many instances of this are on record in the Old World, where they have become so numerous as to call forth governmental intervention. The most notable recent outbreak of this kind in the United States took place in the Humboldt Valley, Nevada, where, during the winters from 1906 to 1908, they swarmed over the cultivated parts of the valley and completely destroyed 18,000 acres of alfalfa, even devouring the roots of the plants. During this outbreak the mice in the alfalfa fields were estimated to number as high as 12,000 to the acre. Whenever field mice become over-abundant notice appears to go out among their natural enemies, and in extraordinary numbers hawks, owls, crows, ravens, sea gulls, coyotes, foxes, bobcats, weasels, and other animals appear to prey upon them. At no season of the year are they free from their foes, for they remain active throughout the winter, and most species apparently lay up no winter store of food. They travel to winter feeding places through series of tunnels under the snow, and it is mainly at this season that they do the most serious damage to orchards and shrubbery. In the far North at the beginning of winter they gather in large numbers about the fur-trading stations and other habitations, where they persistently invade the food supplies. Some of the northern mice, however, gather stores of food for winter. A species living along the coast of the Bering Sea and elsewhere on the Arctic tundra of Alaska accumulates a quart or more of little bulbous grass roots, which are delicious when boiled. They are hidden in nests of grass and moss among the surface vegetation, and before the first snowfall I have seen the Eskimo women searching for them by prodding likely places with a long stick. The roots thus taken from the mice are kept to be served as a delicacy to guests during winter festivals. =THE PINE MOUSE= (=Pitymys pinetorum= and its relatives) (_For illustration, see page 522_) The pine mice form a small group of species peculiar to North America and closely related to the field mice. They are similar in form to the common field mice of the Eastern States, but are usually smaller, with much shorter tails and shorter, finer, and more glossy fur.