Garter snake ‒ sometimes called garden snake or gardener snake ‒ is the common name given to the nearly harmless, small to medium-sized snakes belonging to the genus Thamnophis. Endemic to North America, they can be found from the Subarctic plains of Canada to Central America. The garter snake is the state reptile of Massachusetts. With no real consensus on the classification of species of Thamnophis, disagreement between taxonomists and sources, such as field guides, over whether two types of snakes are separate species or subspecies of the same species is common. Garter snakes are closely related to the genus Nerodia (water snakes), with some species having been moved back and forth between genera. Garter snakes are present throughout most of North America. They have a wide distribution due to their varied diets and adaptability to different habitats, with varying proximity to water; however, in the western part of North America, these snakes are more aquatic than in the eastern portion. Garter snakes populate a variety of habitats, including forests, woodlands, fields, grasslands, and lawns. They almost exclusively inhabit areas with some form of water, often an adjacent wetland, stream, or pond. This reflects the fact that amphibians are a large part of their diet. Garter snakes were long thought to be nonvenomous, but recent discoveries have revealed they do, in fact, produce a mild neurotoxic venom. Despite this, garter snakes still cannot kill humans with the small amounts of comparatively mild venom they produce, and they also lack an effective means of delivering it. They do have enlarged teeth in the back of their mouths, but their gums are significantly larger. The Duvernoy's gland of garters are posterior (to the rear) of the snake's eyes. The mild venom is spread into wounds through a chewing action..