PIT ORGAN

a temperature-sensitive organ in the head of venomous snakes of the subfamily Crotalinae, family Viperidae. Crotalines, known collectively as pit vipers, include rattlesnakes, moccasins, fer-de-lance, and a number of other New World vipers, as well as a few Old World species. The pit organs are located on each side of the face, somewhat below a line from the eye to the nostril. They function in the detection of the small, warm-blooded animals on which the snakes feed, and they aid in orienting the snake's strike.