Collared lemmingDicrostonyx is a genus of rodent in the family Cricetidae. It contains the collared lemmings or varying lemmings. They are the only North American rodents that turn completely white in winter.It contains the following species: Northern collared lemming Ungava collared lemming Nelson's collared lemming Ogilvie Mountains collared lemming Richardson's collared lemming Arctic lemming Unalaska collared lemming