Revision of the Oriental and Australasian diving beetle genus Sandracottus Sharp, 1882 (Coleoptera, Dytiscidae, Dytiscinae).

Abstract

A comprehensive revision is presented of the Oriental and Australasian diving beetle genus Sandracottus Sharp, 1882 (Coleoptera: Dytiscidae: Dytiscinae: Aciliini) and seven junior subjective synonyms are proposed. Sandracottusguerini Balfour-Browne, 1939, syn. nov. is a junior subjective synonym of S.femoralis Heller, 1934; S.manipurensis Vazirani, 1969, syn. nov. of S.hunteri (Crotch, 1872); S.mixtus Blanchard, 1843, syn. nov. of S.chevrolati (Aubé, 1838); and S.angulifer Heller, 1934, syn. nov., S.nauticus Sharp, 1882, syn. nov., and S.palawanensis Satô, 1978, syn. nov. of S.maculatus (Wehncke, 1876). Finally, S.vijayakumari Anand et al., 2021, syn. nov. is a new synonym of S.dejeanii (Aubé, 1838). New status is assigned to S.bakewelliiguttatus (Sharp, 1882), stat. nov. as well as S.hunteri (Crotch, 1872), stat. rev. Lectotypes are designated for the following taxa: Dytiscusflavocinctus Guérin-Méneville, 1830, Hydaticuschevrolati Aubé, 1838, Hydaticusinsignis Wehncke, 1876, Sandracottusbaeri Régimbart, 1899, Sandracottusbizonatus Régimbart, 1899, and Sandracottusornatus Sharp, 1882. A neotype is designated for Hydaticusmaculatus Wehncke, 1876. In total, three Oriental species, two of which also occur in the East Palaearctic, six Southeast Asian species, one species from New Guinea and the Moluccas, and one from Australia with an endemic subspecies in Central Australia (S.bakewelliiguttatus) are recognised. Each taxon is presented with a diagnosis, habitat preferences, conservation assessments, distribution data, and a comprehensive bibliography. Important characters (habitus, dorsal colouration, median lobes and parameres) are illustrated. All currently valid taxa are redescribed. Sandracottusjaechi Wewalka & Vazirani, 1975 from Sri Lanka, S.bizonatus from Borneo, S.insignis from the Philippines and S.rotundus Sharp, 1882 from Sulawesi are recommended to be listed in the next IUCN red data book. A key to all species is provided.