The massasauga (Sistrurus catenatus) is a rattlesnake species found in midwestern North America from southern Ontario to northern Mexico and parts of the United States in between. Like all rattlesnakes, it is a pit viper and is venomous. Adults of S. catenatus are not large, ranging from 60 to 75 cm (24 to 30 in) in length. Their color pattern consists of a grey or tan ground color with a row of large, rounded, brown/black blotches or spots down the center of the back and three smaller rows of alternating spots down each side. Solid black melanistic examples are also known, as well as cases where the back blotches join with those on the sides. Young massasaugas are well-patterned, but paler than the adults. They have heat-sensing pits on each side of their smallish heads, their scales are keeled, and their anal scales are single. (Source: Wikipedia.org, CC BY-SA)