Michael D. Kern / Reticulated Python (Malayopython reticulatus) captive, occurs in South East Asia.

Chris Mattison / Aesculapian snake (Zamenis longissimus) close-up of dorsal scales from a shed skin, showing apical pits, thought to be sensory organs. Native to southern Europe.

James Christensen / Ringed Tree Boa (Corallus annulatus) showing prominent loreal pits for heat sensory, Colon, Panama

Pete Oxford / Timber Rattlesnake (Crotalus horridus) showing heat sensitive pits, northern Georgia