The Mercury Islands tusked wētā, Motuweta isolata, also known as the Middle Island tusked wētā, is a large flightless insect in the family Anostostomatidae, discovered in 1970 living on a single small island in New Zealand. Distinguished by the enormous tusks with which males fight, it was saved from extinction by a captive breeding programme and translocation: the entire world population is descended from a male and two females captured and bred in captivity in 1998, just before the species went extinct in the wild. Motuweta isolata is the largest of the three tusked wētā species, and the most endangered wētā, ranked Nationally Critical by the Department of Conservation.