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 native in Andorra, Croatia, France, Germany, Italy, Monaco, Serbia, Slovenia, Spain, Switzerland. And introduced in Guernsey and Jersey in the British Isles, and the United States. There are also introduced colonies on the south coast of the U.K, notably around Poole Bay in Dorset. Lacerta bilineata reaches an average length (excluding tail) of about 13 centimetres (5.1 in), with a maximum of 40 centimetres (16 in), including tail. The tail may reach up to twice the body length. The average weight is about 35 grams. The body is bright green. The head is bigger in males than in females, and the males often show a blue throat. Juveniles are almost brown, with a yellowish belly and two to four pale, longitudinal lines along the flanks. Sub-adults also have these lines, together with several small brown spots on their backs. These lizards are territorial animals. They feed on arthropods, mainly large insects. They attain sexual maturity at around two years, when they are about 8 cm long (excluding tail). The males fight each other, especially during the mating period, when they are very aggressive towards rivals. The mating ritual is precise, and starts with a bite to the base of the female's tail. The females lay 6 to 25 eggs in a humid and warm site, such as in a decomposing log. The average life span of this species is about 15 years. Its natural habitats are green humid areas, temperate forest, the edges of woods, shrubland, open grassland, arable land, and pastureland. It is threatened by habitat loss.