(genus Heterodon), any of three species of North American nonvenomous snakes belonging to the family Colubridae. They are named for the upturned snout, which is used for digging. These are the harmless but often-avoided puff adders, or blow snakes, of North America. When threatened, they flatten the head and neck, then strike with a loud hiss—rarely biting. If their bluff fails, they roll over, writhing, and then feign death with mouth open and tongue lolling.