Multiple cave invasions by species of the planthopper genus Oliarus in Hawaii (Homoptera: Fulgoroidea: Cixiidae)

Although geologically young, the Hawaiian Islands harbour a rich and remarkably diverse fauna of terrestrial troglobites: more than 70 cave species are known from Kauai, Oahu, Molokai, East Maui, and Hawaii Island. Among the more speciosc groups that have invaded the subterranean biome are the planthoppers (Homoptera Cixiidae) of the genus Oliarus. Five new obligately cavernicolous (troglobitic) Oliarus species which differ in their degree of troglomorphy and male genital structures, are described from lava tubes on the Hawaiian Islands: O. lorettae sp. nov. and O. makaiki sp. nov. from Hawaii Island, O. gagnei sp. nov. and O. ivaikau sp. nov. from Maui Island, and O. kalaupapae sp. nov. from Molokai Island. Short diagnoses of the two troglobitic species already known, 0. polyphemus Fennah, 1973 from Hawaii Island and 0. priola Fennah, 1973 from Maui are provided. Notes on the ecology and distribution of all cavernicolous species are given. Morphological evidence suggests that each of the seven cavernicolous Oliams species from Hawaii represents a separate, independent adaptive shift to underground environments. Potential relationships to the extant epigean species are discussed.