The Bembidion fauna (Coleoptera: Carabidae: Bembidiini) of the Hawaiian Islands is taxonomically revised, entailing the recognition of 23 native, precinctive species, and one adventively introduced Old World species, Bembidion niloticum Dejean. Two species previously placed in Gnatholymnaeum Sharp—G. blackburni Sharp, 1903, and G. spurcum (Blackburn, 1881)—are formally placed as member taxa within Bembidion Latreille, with Gnatholymnaeum recognized at subgenus rank. This taxonomic placement establishes Bembidion blackburni Csiki, 1928, as a junior secondary homonym, and Bembidion ateradustum, new name, is proposed as a replacement. Twenty-one species are recognized as member taxa of Bembidion subgenus Nesocidium Sharp, five of which are newly described: Bembidion waialeale, new species, from Kauai; Bembidion paratomarium, new species, and Bembidion gagneorum, new species, from Oahu; Bembidion kamakou, new species, from Molokai; and Bembidion haleakalae, new species, from East Maui. Bembidion molokaiense Sharp (new synonymy) is treated as a junior synonym of Bembidion ignicola Blackburn, and Metrocidium brevicolle Sharp (new synonymy) is placed as a junior synonym of Bembidion munroi (Sharp). Taxonomic treatment includes a key to species, diagnoses and descriptions of the male genitalia and female reproductive tract for all species, and complete descriptions of external characters for newly described species. Length of the male aedeagal flagellum in subgenus Nesocidium species was found to be subequal in length, to 60–75% longer than the female spermathecal duct, consistent with previous reports that list emplacement of the male spermatophore within the female spermathecal duct as a primary function of the male flagellum. Geographical distribution varies in concert with dispersal ability. All species including at least some individuals with fully developed flight wings are distributed on multiple oceanic islands. Representative taxa within putative clades of vestigially winged species occupy adjacent oceanic islands, implying overwater dispersal by wingless ancestors of present-day species followed by speciation. Ecological preference conforms to the taxon cycle at the archipelago level, with the ancestor of Hawaiian Bembidion hypothesized to have inhabited coastal habitats. Present-day ecological specialists include a deep-soil inhabitant, and numerous species found predominantly in arboreal microhabitats such as mossy vertical tree trunks and horizontal nurse logs. Geographic distributions of the species define areas of endemism appropriate for conservation that are geographically congruent with areas defined by other carabid beetle taxa in Blackburnia Sharp and Mecyclothorax Sharp, as well as by taxa in other insect groups.
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