Hydraena bisinuata, Perkins, 2017

Perkins, Philip D., 2017, Hydraenidae of Madagascar (Insecta: Coleoptera), Zootaxa 4342 (1), pp. 1-264 : 69-72

Hydraena bisinuata , new species

Figs. 58 (habitus), 60 (aedeagus), 255 (map)

Type Material. Holotype (male): Toamasina, Tamatave 6.3 km S Ambanizona, Andranobe Field Station, rainforest, sifted litter from flat sandy areas, some from slope, elev. 25 m, 15° 41' S, 49° 57' E, 14 xi 1993, B. L. Fisher (#886) ( FMNH). Paratype: Same data as holotype (1 FMNH).

Differential Diagnosis. Similar to H. rubrifurcata in size, habitus, and reddish brown color; differentiated therefrom by the flat, non-carinate metaventral plaques and the less strongly punctate dorsum. The aedeagi of the two species markedly differ ( Figs. 60, 71).

Description. Size: holotype (length/width, mm): body (length to elytral apices) 1.79/0.77; head width 0.44; pronotum 0.40/0.57, PA 0.47, PB 0.48; elytra 1.10/0.77.

Dorsum general coloration dark reddish brown; head and pronotal disc darker, almost piceous; anterior border of pronotum very slightly lighter (when teneral pronotal fascia is more apparent); legs dark brown; maxillary palpi reddish brown, distal ½ of last palpomere not darker.

Head with clypeus finely moderately densely punctate; frons slightly more coarsely punctate laterally than medially where interstices ca. 1–2xpd, each puncture with short distinctive seta. Pronotum in anterior and posterior 1/3 slightly more densely punctate than on disc, interstices ca. 0.5–1xpd; punctures on disc smaller, interstices ca. 1–1.5xpd, shining. Mentum moderately coarsely, sparsely punctate, interstices shining; postmentum finely densely punctate. Genae raised, shining, with posterior ridge, interrupted in midline.

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

Elytra weakly arcuate laterally; summit of moderately steep posterior declivity at ca. midlength; lateral explanate margins wide; serial punctures small, round, separated by ca. 1xpd or less, slightly smaller than largest pronotal punctures. Intervals ca. 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. 1/1/3/0.75. P1 almost as wide as P2; median carina very weakly 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 but not contiguous anteriorly, separated basally by slightly less than plaque width, located at sides of median depression. Metaventrite anteromedian carina shorter than plaques, lengths as 3 to 5, 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 with 3 or 4 short sharp spines, surface of tibia notched between spines. Metatibia straight, slender. Metafemur moderately slender. Abdominal apex with small apicomedian notch.

Etymology. Named in reference to the bisinuate pronotum.

Remarks. The holotype is slightly teneral; the pronotal fascia is not as apparent in mature specimens. The aedeagal flagellum illustrated ( Fig. 60) is from a paratype; the flagellum of the holotype is broken off.