Pit vipers range in size from the hump-nosed viper, "Hypnale hypnale", which grows to the length of around 30–45 centimetres (12–18 in), to the South American bushmaster, "Lachesis muta", which is known to grow to a length of 3.65 metres (12.0 ft), making it the longest venomous snake in the New World. Some pit vipers are arboreal (meaning they live in trees), some are terrestrial (meaning they live on the ground), and one species is even semi-aquatic: the cottonmouth, "Agkistrodon piscivorus".