Subgenus Risa Becker Risa Becker, 1907:404. Type species: Risa longirostris Becker, 1907:404 [monotypy].—Hennig, 1937:75 [redescription].— Papp, 1984: 178 [Palearctic catalog, as a genus]. Diagnosis. The subgenus Risa is distinguished from the subgenus Achaetorisa by the following combination of characters: Head: Face usually with a conspicuous, medial carina, in lateral view carina pointed (carina inconspicuous in R. kotrbae). Thorax: Prescutellar acrostichal setae usually well developed (absent in R. kotrbae); scutellar disc bearing a few, scattered setulae. Costal section III (between R 2+3 and R 4+5) bearing approximately 70–80, densely spaced setulae. Abdomen: Male terminalia: Cercus fused ventrally with epandrium; gonostylus either lacking or more likely fused indistinguishably with ventral margin of epandrial arm; hypandrium wider than long, almost band-like, transverse. Female terminalia: Subanal plate present; sternite 8 interrupted or thin dorsomedially, often with a sclerotized, protrusion (Fig. 33); posterior portion of sternite 8 bearing (1) numerous, mostly straight setae (R. asiatica), (2) numerous straight and some hooked setae (R. flavipalpis), or (3) numerous, long, hooked setae (R. longirostris, R. longicornuta, R. kotrbae); anterior margin of sternite 8 bearing numerous long setulae; cerci short and rounded; stalk of ventral receptacle lacking paired, tubular processes (Fig. 15). Discussion. We recognize the following five species in the nominate subgenus Risa: R. (R.) asiatica Ozerov, R. (R.) flavipalpis Ozerov, R. (R.) kotrbae sp. nov., R. (R.) longicornuta Papp, R. (R.) longirostris Becker (R. mongolica Papp is possibly conspecific).

Published as part of Mathis, Wayne N. & Zatwarnicki, Tadeusz, 2023, Phylogeny and Taxonomy of the Risa Genus-group (Diptera: Ephydridae), with Description of a New Genus from Australia, pp. 1-23 in Records of the Australian Museum (Rec. Aust. Mus.) (Rec. Aust. Mus.) 75 (1) on page 20, DOI: 10.3853/j.2201-4349.75.2023.1823, http://zenodo.org/record/7946210