Hydraena oscillata, Perkins, 2017

Perkins, Philip D., 2017, Hydraenidae of Madagascar (Insecta: Coleoptera), Zootaxa 4342 (1), pp. 1-264 : 45-46

Hydraena oscillata , new species

Figs. 34 (habitus), 36 (aedeagus), 243 (map)

Type Material. Holotype (male): Toamasina, 18.7697S 48.4372E, Alaotra Mangoro Andasibe-Mantadia NP, Mantadia: 15km N of park entrance , forest stream with small pools, elev. 930 m, 28 xi 2014, J. Bergsten, R. Bukontaite, J.H. Randriamihaja, T. Ranarilalatiana & S. Holmgren ( MAD14-82 ) ( NHRS). Paratypes: Same data as holotype (2 NHRS) .

Differential Diagnosis. Similar in color and size to H. bergsteni , but having a differently shaped pronotum that is more coarsely punctate, and elytra that are more ovate. The aedeagi of the two species differ markedly ( Figs. 32 , 36). Clearly related to H. furcula based on general structure of the aedeagus, but easily distinguished therefrom by the size and color differences, and the different shapes of the paramere and distal processes, and thickness of the main piece ( Figs. 35, 36).

Description. Size: holotype (length/width, mm): body (length to elytral apices) 2.37/0.98; head width 0.54; pronotum 0.58/0.70, PA 0.61, PB 0.63; elytra 1.46/0.98.

Head piceous, pronotum and elytra dark brown, anterior border of pronotum and humeral angles of elytra slightly lighter; legs dark brown; maxillary palpi reddish brown, distal ½ of last palpomere not darker.

Head with clypeus finely densely punctate; frons more coarsely punctate than clypeus, especially laterally where interstices narrow walls, medially interstices ca. 0.5–1xpd, each puncture with short seta. Pronotum densely coarsely punctate throughout, interstices ca. 0.5–1xpd, shining. Mentum and postmentum coarsely, densely punctate, rugulose, interstices shining. Genae raised, shining, with deeply demarcated posterior ridge, interrupted in midline.

Pronotum bisinuate; anterior margin straight behind eyes, emarginate behind frons; PF1 and PF2 absent; PF3 moderately deep; PF4 shallow; PF3 and PF4 shallowly confluent.

Elytra weakly arcuate laterally; summit of rather steep posterior declivity at ca. midlength; lateral explanate margins wide; serial punctures round, separated by ca. 0.5–1xpd, slightly smaller than largest pronotal punctures. Intervals ca. 0.5–1xpd; discal intervals weakly raised, shining. Apices in dorsal aspect rather sharply conjointly rounded, in posterior aspect margins not forming angle with one another.

Ratios of P2 width and plaque shape (P2/w/l/s) ca. 1/1/2/1. P1 width ca. 0.5x P2; median carina sinuate in profile. P2 l/w ca.2/1, sides parallel, apex blunt and on same level as anteromedian carina of metaventrite. Plaques roundly raised, converging and anteriorly contiguous with anteromedian carina, separated basally by slightly more than plaque width, located at sides of median depression. Metaventrite anteromedian carina shorter than plaques, as 10 to 13, joining anterior level of plaques, together forming inverted Y-shape; long and strong, slightly arcuate longitudinal ridge on each side, extended posteriorly from margin of each mesocoxal cavity. AIS width at arcuate posterior margin ca. 1.5x P2. Protibia straight, slender. Mesotibia very slightly arcuate, medial margin over ca. middle 1/3 with 5 or 6 short sharp spines. Metatibia very slightly arcuate in distal 1/3, slender. Metafemur moderately slender. Abdominal apex with small apicomedian notch.

Etymology. Named in reference to the tuning fork shape of the metaventral carinae.

Figures

FIGURE 34. Hydraena oscillata, holotype, habitus dorsal, lateral, and ventral.

FIGURES 31 – 32. Hydraena, aedeagi of H. impressicollis (lectotype) and H. bergsteni (holotype).