1. A pit viper (Agkistrodon contortrix, subfamily Crotalinae) that occurs in eastern North America. Named for the colour of its head, it grows to about 90 cm, and has a broad head and distinct neck. Its camouflage and habit of lying immobile if threatened mean people sometimes encounter it accidentally. Its bite is painful but rarely fatal.

2. The common name for three species of Austrelaps venomous snakes (family Elapidae) found in southern Australia; their bite can be fatal if untreated.

3. A nocturnal pit viper, Deinagkistrodon acutus, found in mountainous regions of southern China, northern Vietnam, and perhaps Laos. Its bite is often fatal.

4. A non-venomous colubrid snake, Coelognathus radiates (family Colubridae), also known as the copper-headed trinket snake, copperhead rat snake, and radiated ratsnake, found in the Indian subcontinent, China, and South East Asia.