Rattlesnakes are a group of venomous snakes, genera Crotalus and Sistrurus. They belong to the class of venomous snakes known commonly as pit vipers. Rattlesnakes are characterized by the presence of a "rattle" at the tip of the tail used to warn off predators and threats. Overview There are approximately fifty species of rattlesnake, with numerous subspecies. They receive their name for the rattle located at the tip of their tails. The rattle is used as a warning device when threatened. The sc… (More on Rattlesnake)