Hydraena (Hydraenopsis) reducta, Perkins, 2023

Perkins, Philip D., 2023, New Neotropical and Nearctic species of water beetles in the genera Hydraena Kugelann and Ochthebius Leach, a key to North American genera and subgenera of the family, new distribution records, and a synopsis of ecology, behavior and morphology related to aquatic life (Coleoptera: Hydraenidae), Zootaxa 5367 (1), pp. 1-86 : 24

Hydraena (Hydraenopsis) reducta , new species

Figs. 3 (habitus comparison), 13 (habitus and aedeagus)

Type Material. Holotype (male): “ MEXICO: Mexico 7miNE Temascaltepec, 7000’ ix.12 –15.1973 // under moss on rock mass A. Newton ” ( FMNH) . Paratype: Estado de México, Nezahualcóyotl, Tamazuchale , 21.iv.2004, 19°03’12’’N, 100°01’83’’W, 1850 m, s/colector (1 male IEXA) .

Differential Diagnosis. This new species is a member of the H. leechi Group (see Perkins 1980: 65), having a large pronotal scintilla, lacking metaventral plaques, and males having brushes of setae on the metatibiae. It will key to H. leechi in Perkins (1980: 66). Externally it differs from H. leechi in being smaller (ca. 1.70 vs. 1.80 mm), slightly less coarsely densely punctate on the head and pronotum, having the pronotum more widely arcuate laterally, the elytra larger compared to the size of the pronotum, and the mesoventral intercoxal process very narrow (l/w ca. 7/1. Dissection of males and careful examination of the aedeagus will be necessary for completely reliable determinations ( Fig. 13 ).

Description. Size: holotype (length/width, mm): body (length to elytral apices) 1.71/0.72; head width 0.42; pronotum 0.42/0.58, PA 0.45, PB 0.52; elytra 1.08/0.72. Habitus as illustrated ( Fig. 13 ). Dorsum of head dark brown to piceous; pronotum brown around dark brown disc; elytra dark brown; legs light brown; maxillary palpi light brown to testaceous, tip not darker. Frons punctures ca. 1–1.5xef, slightly larger and denser near eyes than medially; interstices laterally mcr, dull, medially shining, ca. 1xpd. Clypeus mcr, dull, laterally, medially slightly raised, shining, finely sparsely punctulate. Mentum mcr, dull.

Pronotum rather widely arcuate laterally; anterior margin straight behind eyes, emarginate behind frons, except produced in midline at large scintilla; punctures on disc much larger and deeper than those of frons, interstices shining, narrow walls to ca. 1xpd, punctures larger and denser at anterior and posterior; PF1 absent; PF2 shallow; PF3 and PF4 moderately deep.

Elytra weakly arcuate laterally; summit of posterior declivity at about posterior 1/3; lateral explanate margins wide; on basal 1/3 punctures slightly smaller than largest pronotal punctures, punctures becoming finer and more widely spaced beyond posterior declivity. Intervals not raised, shining, on basal 1/3 ca. 1xpd or slightly smaller, as are interstices between punctures of a row. Apices in dorsal aspect conjointly, rather widely rounded, in posterior aspect margins forming deep angle with one another.

Venter: Mentum densely finely punctulate, dull; postmentum very finely very densely micropunctulate in median area, surrounding areas smooth, shining. Genae raised, shining, with low posterior ridge laterally.

P1 laminate; median carina sinuate in profile. P2 very narrow, l/w ca. 7/1, sides converging toward blunt apex, apex raised slightly above mesoventral intercoxal process. Plaques absent, median depression deep. AIS width at straight posterior margin ca. 5x P2. Pro- and mesotibiae straight, slender. Metatibia very weakly arcuate, with brush of setae on inner margin over distal 1/3. Abdominal apex symmetrical; last tergite with apicomedian indentation.

Distribution. Currently known only from the type locality.

Etymology. Named in reference to the very narrow mesoventral intercoxal process and the absence of metaventral plaques.

Figures

FIGURE 3. Dorsal habitus of Hydraena species, H. leechi Group.

FIGURE 13. Hydraena (Hydraenopsis) reducta new species, holotype habitus and aedeagus.