Lizard heads called the parietal eye, a basal ("primitive") feature also present in the tuatara. This "eye" has only a rudimentary retina and lens and cannot form images, but is sensitive to changes in light and dark and can detect movement. This helps them detect predators stalking it from above. Until 2006 it was thought that among lizards, only the Gila monster and the Mexican beaded lizard were venomous. However, several species of monitor lizards, including the Komodo dragon, produce powerful venom in their oral glands. Lace monitor venom, for instance, causes swift loss of consciousness and extensive bleeding through its
Western green lizard Western green lizard The western green lizard (Lacerta bilineata) is a wall lizard of the Lacertidae family. The genus name "Lacerta" and the species name "bilineata" are Latin words respectively meaning “lizard” and “with two lines”, with reference to the pale lines present on the flanks of the young individuals. It is found in Andorra, Croatia, France, Germany, Italy, Monaco, Serbia, Slovenia, Spain, Switzerland, on Jersey in the British Isles, and the United States. There are also colonies on the south coast of the U.K, notably around Poole Bay in Dorset. "Lacerta bilineata" reaches an average length (excluding tail) of