The taxonomic status of the subgenera of Lepidocyrtus Bourlet is confused. Currently ten subgenera are recognised but their separation, using the existing set of diagnostic characters, is not clear. Collections over the last forty years have shown that species of Setogaster Salmon, originally described as a genus (Trichogaster Handschin) and currently considered a subgenus of Lepidocyrtus, are common and widespread in Australia. The diagnostic characters of Setogaster, as given by Handschin, are: 1) the basal mucronal spine with spinelet; 2) lack of scales on antennae, legs, ventral tube and dorsal region of manubrium; and, for some species, 3) tufts of long filaments laterally on abdomen III. These three diagnostic characters for Setogaster are shared with some other subgenera, making their delimitation unclear. We provide here an array of new characters that are associated with Handschin's characters which separate Setogaster from all European species of the subgenera Lanocyrtus and Lepidocyrtus s. str. On this basis we define subgenus Setogaster more in detail, redescribe some species in the subgenus, corroborate the presence of the subgenus in many Australian localities, and confirm three records of exotic, introduced species in Australia. Lepidocyrtus nigrofasciatus Womersley, Lepidocyrtus praecisus Schott, and the Hawaiian Lepidocyrtus kuakea Christiansen & Bellinger, are placed in Setogaster subgenus; Lepidocyrtus (Trichogaster) pallida Salmon from Singapore is placed in the subgenus Acrocyrtus; Merapicyrtus Yoshii & Suhardjono is considered a synonym of Setogaster.
Characters of two species, described more than seventy years ago in the genus Arrhopalites Börner, A. coccineus Salmon, 1941 and A. adelaidica Womersley, 1933, are not consistent with the current diagnosis of the genus. Instead, the holotype of A. coccineus and two cotypes of A. adelaidica, but not the lectotype, are consistent with characters of Stenacidia violacea (Reuter, 1881) following the description of the genus and species published by Bretfeld (1999). Stenacidia violacea is the type species of its monotypic genus. As the characters of the genus Stenacidia, following Bretfeld (1999), are very different to those of Arrhopalites, but are consistent with the characters of A. coccineus and two cotypes of A. adelaidica, A. coccineus is synonymised with S. violacea here and identification of the cotypes of A. adelaidica corrected.