Answer
The pits of pit vipers and other snakes ( Boidae and Crotalinae) are heat-sensitive organs. Pits help pit vipers to sense, track and locate warm blooded prey in darkness or reduced light.
Work Step by Step
Heat sensitive pit organs are found in several kinds of snakes--it vipers ( subfamily Crotalinae) are most infamous/notorious, but boas ( Boidae) , pythons, rattlesnakes, copperheads, and bushmaster snakes all have heat sensitive organs. These heat sensitive organs (pits) are usually located between eye and nostril on either side of the head. They can detect a difference in temperature as low as 0.004 deg. C. Because of this stereoscopic heat ( infra red rays) sensitivity, these snakes are able to detect predators or prey in complete darkness. They can track warm prey and strike a warm target as effectively in total darkness as in light.
