Family Viperidae Crotalus atrox , Western Diamondback Rattlesnake Introduction Most poisous snakes in the United States belong to the family Viperidae, subfamily Crotalinae, and pit vipers.
Pit vipers are a group of venomous snakes that have depressions in the front of their eyes.
These pits regulate the amount of venom injected into their prey to kill the animal. Their two parted tongue enables the rattlesnake to smell. The delicate tip of the tongue carries particles to Jacobson's organs. These two pits which are found in the mouth enable the snake to designate how far right or left the prey is from them. Species classification is dependent upon scale morphology and patterns .