Hawaiian Paratachys Casey (Coleoptera, Carabidae): small beetles of sodden summits, stony streams, and stygian voids

Five Hawaiian species of Paratachys Casey are revised, including four newly described: Paratachys terryli from Kauai; P. perkinsi from Moloka‘i; P. haleakalae from Maui; and P. aaa from Hawai‘i Island. A lectotype is designated for the fifth Hawaiian species currently combined with Paratachys, Tachys arcanicola Blackburn, 1878 of Oahu. Hawaiian Paratachys spp. known from more than one specimen exhibit some degree of ocular polymorphism, that variation being extreme in P. terryli where individuals range in ocular development from macrophthalmic with broadly convex eyes to microphthalmic with small, flat eyes. All Hawaiian Paratachys species comprise individuals with vestigial wings, with the exception of P. terryli, where a single macropterous, macrophthalmic female complements the other 18 brachypterous specimens. Based on a transformation series of characters from the male aedeagus, the biogeographic history of Hawaiian Paratachys is consistent with progressive colonization of the Hawaiian Island chain. Three of the species do not appear to represent species of conservation concern, with P. terryli and P. haleakalae known from terrestrial deep soil, litter, and streamside microhabitats in montane wet rain forest, and the troglobitic P. aaa occupying the dark zone of numerous, recently developed lava tube caves within the Mauna Loa and Kilauea volcanic massifs. The conservation status of the other two species is much more dire, with P. arcanicola of O‘ahu not seen in nature since the early 20th Century, and P. perkinsi known only from a single specimen fortuitously collected in 1894 near sea level on Moloka‘i