Lemming (Myodes), a genus of mouse-like Rodents, with four species from Scandinavia, Siberia, and arctic and sub-arctic America. They are allied to the vole (q.v.), but are more stoutly built. The Scandinavian (M. lemmus), about 5 inches long, with brownish-yellow fur spotted with black, migrates periodically in vast troops, which go east or west from the central plateau till they reach the sea, into which they plunge with the vain expectation of crossing it, as they have already crossed the lakes and rivers that lay in their course. The Banded Lemming [Caniculus torquatus), the sole species of the genus, has no external ears.