Hydraena (Hydraenopsis) bicandida, 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 : 15

Hydraena (Hydraenopsis) bicandida , new species

Figs. 1 (habitus comparison), 7 (habitus and aedeagus)

Type Material. Holotype (male): “ MEXICO: Mexico 7 mi NE Temascaltepec , 7000’ ix.12–15.1973 // under moss on rock mass A. Newton ” ( FMNH).

Differential Diagnosis. This new species is a member of the H. argutipes Subgroup of the H. leechi Group; the subgroup is previously known from nine species (see Perkins 1980: 37, 151). Based on the aedeagal morphology, this species is clearly related to H. argutipes Perkins 1980 . It is recognized by the combination of the large, brightly shining metaventral plaques, the deep pronotal foveae, the lack of a pronotal scintilla, and the aedeagus ( Fig. 7 ). Reliable determinations will require dissection of males to separate this species from others in the H. argutipes Subgroup.

Description. Size: holotype (length/width, mm): body (length to elytral apices) 1.38/0.60; head width 0.36; pronotum 0.33/0.48, PA 0.38, PB 0.42; elytra 0.87/0.60. Habitus as illustrated ( Fig. 7 ). Dorsum dark brown to black, palpi brown, tip of last palpomere darker. Dorsum of head and pronotum moderately coarsely moderately densely punctulate, interstices shining. Punctures of frons disc ca. 1xef, interstices 1–2xpd on disc, shining, lateral areas microreticulate, dull; punctures of clypeus very fine, lateral areas microreticulate. Punctures of pronotal disc deep, ca. 2–3xef, interstices on pronotal disc ca. 1–2xpd. All dorsal punctures with very indistince, very short recumbent seta. Labrum apicomedially excised, free margins weakly upturned.

Pronotum with anterior margin very weakly emarginate over middle ½, without scintilla; anterolateral, posterolateral and posteromedial foveae deep; anterior part of disc with transverse impression.

Elytra with summit of posterior declivity slightly past midlength; lateral explanate margins moderately wide; on basal 1/3 punctures ca. 1xpd of largest pronotal punctures, or slightly larger, punctures becoming gradually smaller toward posterior; most punctures with minute granule at anterior margin. Intervals not raised, width ca. 1xpd, as are interstices between punctures of a row.Apices in dorsal aspect conjointly, rather sharply rounded, in posterior aspect margins not forming angle with one another.

Venter: Mentum very sparsely very finely punctulate, shining; postmentum very finely densely micropunctulate in median concavity, surrounding areas smooth, shining. Genae raised, shining, without posterior ridge. Ratios of P2 width and plaque shape (P2/w/l/s) ca. 1/2/5/2. P1 laminate; median carina sinuate in profile. P2 l/w ca. 4/1, sides slightly converging toward blunt apex, apex raised slightly above mesoventral intercoxal process. Plaques large, brightly shining, parallel, slightly raised, narrowly separated by slightly less than plaque width. AIS width at straight posterior margin ca. 2x P2. Protibia slightly arcuate. Mesotibia straight, slender. Metatibia slightly widened over distal 2/3. Abdominal apex symmetrical; last tergite with apicomedian notch.

Distribution. Currently known only from the type locality.

Etymology. Named in reference to the brightly shining metaventral plaques.

Figures

FIGURE 1. Dorsal habitus of Hydraena species.

FIGURE 7. Hydraena (Hydraenopsis) bicandida new species, holotype habitus and aedeagus.