The Collaborative International Dictionary of English v.0.48:

harlequin snake \har"le*quin snake`\ n.
   any of several venomous New World snakes brilliantly banded
   in red and black and either yellow or white, especially the
   eastern coral snake, a small poisonous snake (Micrurus
   fulvius or Elaps fulvius), ringed with red and black,
   found in the Southeastern United States. They are widely
   distributed in Southern and Central America;

   Syn: coral snake, New World coral snake.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

eastern coral snake
    n 1: ranges from Central America to southeastern United States
         [syn: eastern coral snake, Micrurus fulvius]