A lemming is a small rodent, usually found in or near the Arctic in tundra biomes. Lemmings make up the subfamily Arvicolinae (also known as Microtinae) together with voles and muskrats, which form part of the superfamily Muroidea, which also includes rats, mice, hamsters, and gerbils. In popular culture, a longstanding myth holds that they jump off cliffs and commit mass suicide.

 

Note:   The above text is excerpted from the Wikipedia article Lemming, which has been released under the GNU Free Documentation License.