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).