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(Masticophis, sometimes Coluber, flagellum), nonvenomous snake of the family Colubridae that ranges from the southern half of the United States to west central Mexico. It averages 1.2 metres (4 feet) long, but it is occasionally twice that length. It is slender, and its tail is marked like a plaited whip. The eastern subspecies is brownish; western subspecies tend to be reddish (red racer or whip snake) or black (western black racer).