pit viper

pit viper poisonous snake of the family Crotalidae, primarily a New World family. Like the Old World true vipers (family Viperidae), pit vipers have long, hollow, erectile fangs that are folded back against the roof of the mouth except when the snake is striking. In addition, the pit vipers have developed special organs of heat reception that help them to sense warm-blooded animals, an ability that is especially useful at night, when many of them hunt. These organs consist of pits, for which the group is named, located just behind the nostrils and covered with a temperature-sensitive membrane. Some pit vipers may also use these organs to find cool refuges from inhospitable daytime temperatures.

The largest group of pit vipers is the rattlesnake genus Crotalus, found in North, Central, and N South America. Other New World forms are the fer-de-lance (genus Bothrops ) and the bushmaster (genus Lachesis ). The genus Ancistrodon includes the copperhead and water moccasin , as well as about a dozen Asian species. Pit vipers are classified in the phylum Chordata , subphylum Vertebrata, class Reptilia, family Crotalidae.

pit vipers See CROTALIDAE.

Crotalidae (pit vipers; order Squamata, suborder Serpentes) A family of venomous snakes which are closely related to true vipers (Viperidae) but which have heat-sensitive pit organs just behind the nostrils. Their diet consists mainly of birds and small mammals. Tail-rattling mechanisms have been developed in advanced forms (rattlesnakes); these are formed from loosely connected horny segments more of which are added to the ‘rattle’ at each moult. Crotalus horridus (timber rattlesnake) grows up to 1.8 m long and occurs in woodland in the eastern USA. C. cerastes (sidewinder) is small (up to 60 cm) and occurs in the deserts of the southwestern USA; it has a small horn above each eye and its common name is derived from its method of locomotion across soft sand: it proceeds diagonally by throwing its body forward in loops (‘sidewinding’ also occurs in some vipers). There are approximately 130 species in the family, occurring in the Americas and tropical Asia.