In New Mexico, Arizona, and northern Mexico the only existing poisonous lizards, the Gila Monster (_Heloderma_) (fig. 126) is found. This is a heavy, deep-black, orange-mottled lizard about sixteen inches long. There is much variance of belief among people regarding the Gila Monster, but recent experiments have proved the poisonous nature of the animal. The poison which is secreted by glands in the lower jaw flows along the grooved teeth into the wound. A beautiful and interesting little lizard found in the South is the green chameleon (_Anolis principalis_). Its body is about three inches long with a slender tail of five or six inches. The normal color of the chameleon is grass-green, but it may "assume almost instantly shades varying from a beautiful emerald to a dark and iridescent bronze color." In the tropics many of the lizards reach great size and are of strange shape and patterns. The flying dragons (_Draco_) have a sort of parachute on each side of the body composed of a fold of skin supported by five or six false posterior ribs. These lizards live in the trees of the East Indies and "fly" or sail from tree to tree. They are very beautifully colored. The iguanas (_Iguana_) of the tropics of South America are commonly used for food. They live mostly in trees, and reach a length of five or six feet. The monitor (_Varanus niloticus_) is a great water-lizard that lives in the Nile, and feeds on crocodiles' eggs, of which it destroys great numbers. It is the principal enemy of the crocodile. When full grown it reaches a length of six feet or even more.