Curvosa Group The Curvosa Group comprises three species: H. curvosa (Brazil, Peru), H. takutu (Guyana), and H. hintoni (Brazil). These are rather convex species, moderately sized (ca. 1.48–1.76 mm), with a characteristic habitus (Figs. 16– 18). The coxae are rather widely separated by P1 and especially P2, and the plaques are also widely separated. The genae usually have an ill-defined posterior ridge laterally. The male genitalia are quite stout, and have a basic plan similarity; the parameres are moderately large, and the right paramere has modified setae (Figs. 15, 19, 20). The female gonocoxite is "divided", having a weakly sclerotized midlongitudinal area, and is similarly shaped in all species in this group (e.g., Fig. 149). The spermatheca (Figs. 151–152) is circular, somewhat disc-shaped, markedly differing from that of all American Hydraena, except members of the Paeminosa Group. Externally and male genitalically the two groups are very different. Two of the species in this group, H. curvosa and H. takutu, so far have only been collected from leaf packs taken from streams.

Published as part of Perkins, Philip D., 2011, New records and description of fifty-four new species of aquatic beetles in the genus Hydraena Kugelann from South America (Coleoptera: Hydraenidae), pp. 1-198 in Zootaxa 3074 on page 19, DOI: 10.5281/zenodo.1050060