Hydraena curvosa, new species Figs. 16 (habitus), 19 (aedeagus), 149 (female abd.), 152 (spermatheca), 194 (map) Type Material. Holotype (male): Brazil: Para, Rio Xingu Camp, Altamira (ca 60km S.), 1st jungle stream on trail 4, colln. #6, 3° 39' S, 52° 22' W, 13 x 1986, P. J. Spangler & O. S. Flint. Deposited in the USNM. Paratypes (83): Brazil: Para, Altamira (ca 22km SE), stream below waterfall at Caverna do Tatajuba, colln. #11, 6 x 1986, P. J. Spangler & O. S. Flint (13 USNM); Rio Xingu Camp, Altamira (ca 60km S.), 1st jungle stream on trail 4, colln. #6, 3° 39' S, 52° 22' W, 3 x 1986, P. J. Spangler & O. S. Flint (9 USNM); same locality, 3° 39' S, 52° 22' W, 13 x 1986, P. J. Spangler & O. S. Flint (54 USNM); Peru: Madre de Dios, Tambopata, Terrafirme, Drinking Quebroda, ex leaf packs, 13° 0' S, 69° 33' W, 11 ix 1983, J. J. Anderson (7 USNM). Differential Diagnosis. Similar in dorsal habitus to H. takutu and H. hintoni (Figs. 16–18); differentiated from both species by the more transverse pronotum that is more markedly sinuate laterally, and the very convex elytra. The metaventral plaques are carinate, similar to those of H. hintoni; however, the hind tibiae of males differ markedly in the two species. The male genitalia of the three species also show a relationship (Figs. 15, 19–20). Description. Size: holotype (length/width, mm): body (length to elytral apices) 1.76/0.77; head 0.30/0.39; pronotum 0.37/0.52, PA 0.43, PB 0.46; elytra 1.09/0.77. Dorsum of head with frons dark brown to piceous, clypeus brown; pronotum brown except disc dark brown, diffusely margined; elytra dark brown; legs brown; maxillary palpi testaceous, tip not darker. Frons punctures ca. 1–1.5xef, larger and denser near eyes than medially; interstices shining, 0.5–1xpd laterally, 3–5xpd medially. Clypeus very finely sparsely punctate. Mentum and postmentum very sparsely very finely punctulate, shining. Genae raised, shining, lateral 1/3 on each side with low posterior ridge. Pronotum subcordiform, sides sinuate both in front of and behind arcuate middle, turning outward basally, posterior angles acute; anterior margin rather markedly emarginate, scintilla absent; punctures on disc much larger and deeper than those of frons, interstices shining, 0.5–3xpd, punctures larger and denser at anterior and posterior; PF1 and PF2 absent; PF3 and PF4 deep, shallowly confluent; indistinct low ridge between PF3 and lateral margin. Elytra appearing humped, very convex at summit of posterior declivity, slightly before midlength; lateral explanate margins rather wide; on basal 1/3 punctures ca. 1xpd largest pronotal punctures, punctures becoming much finer and much more widely spaced toward posterior. Intervals not raised, shining, on basal 1/3 ca. 1–3xpd, as are interstices between punctures of a row, a few punctures subserial. Apices in dorsal aspect conjointly rounded, in posterior aspect margins forming very shallow angle with one another. Ratios of P2 width and plaque shape (P2/w/l/s) ca. 5/1/7/9. P1 not laminate, width ca. 1/2 P2; median carina sinuate in profile. P2 wide, l/w ca. equal, sides slightly converging toward rounded and slightly deflexed apex, apex not raised above mesoventral intercoxal process. Plaques widely separated, narrow carinate lines, parallel, located at sides of median depression. Metaventrite with low median carina anteriorly and with very short longitudinal ridge on each side, extended posteriorly from margin of each mesocoxal cavity. AIS width at straight posterior margin ca. 2x P2. Protibia slightly arcuate, slightly gradually increasing in width from base to apex. Meso- and metatibia slender, straight. Male abdominal apex asymmetrical; last tergite with very small apicomedian notch. Female (microslide mount, n=1): last tergite sharply rounded, without apicomedian notch, ca. 20 slightly hooked, long, slender, widely spaced setae; gonocoxite divided by weakly sclerotized midlongitudinal area, apical margin almost transverse, lacking transverse ridge; spermatheca disc type (Fig. 152). Etymology. Named in reference to the curvaceous habitus. Distribution. Currently known from northeastern Brazil and one very disjunct locality in Peru (Fig. 194).

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 pages 19-20, DOI: 10.5281/zenodo.1050060