a variety of mammals have been introduced: donkeys, sheep, cats and rats among others. reptiles consist of two species of lizards. endemic insect species include the minute, wingless psocopteran "troglotroctes ashmoleorum", that has been found in caves and between lava blocks. in summer, flies are known to be a problem. the largest native land animal is the land crab "johngarthia lagostoma" (formerly "gecarcinus lagostoma"). offshore, there is a variety of open-ocean fish, including sharks, wahoo, tuna, bonito, barracuda, marlin, blackfish and sailfish. the protected green turtle is perhaps the most notable of the endemic fauna, coming ashore to lay their eggs on the beaches from november to may. turtles were regularly harvested until 1930, when the practice was banned. by 1970 the turtle population had begun to rebound. from the 1970s, when records began, to 2014, green turtle nesting increased by 500%, resulting in some 24,000 nests being laid on the island's main beaches each year.