Hydraena multiarcuata, Perkins, 2017

Perkins, Philip D., 2017, Hydraenidae of Madagascar (Insecta: Coleoptera), Zootaxa 4342 (1), pp. 1-264 : 62-64

Hydraena multiarcuata , new species

Figs. 50 (habitus), 52 (aedeagus), 251 (map)

Type Material. Holotype (male): Fianarantsoa, Ranomafana, Sahamalaotra , elev. 1123 m, 21° 16' S, 47° 25' E, 1 xi–30 xii 2004, M. Balke (MD 031) ( ZSMC).

Differential Diagnosis. Differentiated from other members of the species group by the combination of the arcuate meso- and metatibiae, the arcuate metaventral plaques, and the arcuate elytra. The aedeagus perhaps has some very superficial resemblance to that of H. ranomafana , but differs in many respects of both distal and main piece, and size ( Figs. 52, 55).

Description. Size: holotype (length/width, mm): body (length to elytral apices) 1.55/0.70; head width 0.37; pronotum 0.35/0.52, PA 0.41, PB 0.44; elytra 0.93/0.70.

Holotype teneral, mature color most likely with dorsum reddish brown, head darker than pronotum (piceous in darkest specimens); pronotum lighter than elytra; legs light brown to testaceous; maxillary palpi testaceous, distal ½ of last palpomere not darker.

Head with clypeus finely sparsely punctate medially, laterally very weakly microreticulate; frons more coarsely punctate laterally than medially where interstices ca. 1–4xpd. Pronotum in anterior and posterior 1/3 more densely punctate than on disc, interstices ca. 0.5–1xpd; punctures on disc distinctly smaller, interstices ca. 1–3xpd, shining. Mentum finely microreticulate, dull; postmentum finely microreticulate medially. Genae raised, shining, with posterior ridge, interrupted in midline.

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

Elytra weakly arcuate laterally; summit of steep posterior declivity slightly before midlength; lateral explanate margins wide; serial punctures round, large and deeply impressed, especially on basal 0.5, separated by ca. 1xpd, larger than largest pronotal punctures. Intervals not raised, shining, ca. 0.5–1xpd. 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. 1/0.5/2/2. P1 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 narrow, subcarinate, arcuate and slightly converging anteriorly, separated basally by ca. 2– 3x plaque width, located at sides of median depression. Metaventrite anteromedian carina slightly longer than plaques, attaining anterior level of plaques; long longitudinal ridge on each side, extended posteriorly from margin of each mesocoxal cavity. AIS width at arcuate posterior margin ca. 2x P2. Protibia slightly arcuate. Mesotibia distinctly arcuate, medial margin with 4 or 5 short sharp spines, spines longer and stronger from most proximal to most distal, surface of tibia notched between spines. Metatibia arcuate, slender. Metafemur slender, arcuate on lateral margin, sinuate on medial margin. Abdominal apex with narrow apicomedian notch.

Etymology. Named in reference to the arcuate meso- and metatibiae, the arcuate elytra, and the arcuate metaventral plaques.