Hydraena arta, Perkins, 2017

Perkins, Philip D., 2017, Hydraenidae of Madagascar (Insecta: Coleoptera), Zootaxa 4342 (1), pp. 1-264 : 149-150

Hydraena arta , new species

Figs. 135 (habitus), 137 (aedeagus), 293 (map)

Type Material. Holotype (male): Antsiranana, Parc National de Marojejy, Manantenina River, 28.0 km 38° NE Andapa, 8.2 km 333° NNW Manantenina, sifted litter (leaf mold, rotten wood), rainforest, elev. 450 m, 14° 26' S, 49° 46' E, 12–15 xi 2003, B.L.Fisher et al. (BLF 8722) ( CAS). Paratypes: Same data as holotype (37 CAS).

Differential Diagnosis. Similar to H. bucollis in size (ca. 1.19 mm), color, dorsal punctation, and pronotal foveae; differing therefrom in having a differently shaped pronotum, a very narrow prosternal intercoxal process, presence of metaventral plaques, and, in males, having the metatibiae very slightly arcuate, the distal ½ of the medial margin emarginate and with a small brush of setae in a unilinear row. In both species the only pronotal fovea present is PF3. The aedeagi of the two species differ markedly ( Figs. 130, 137).

Description. Size: holotype (length/width, mm): body (length to elytral apices) 1.19/0.53; head width 0.33; pronotum 0.30/0.44, PA 0.36, PB 0.40; elytra 0.75/0.53.

Dorsum testaceous to ochraceous, pronotum slightly lighter than elytra; legs testaceous; maxillary palpi testaceous, distal ½ of last palpomere not darker.

Head with clypeus and frons finely sparsely punctate, interstices shining. Pronotum finely punctate; interstices ca. 1–3xpd on disc, shining. Mentum sparsely finely punctulate, weakly shining; postmentum sparsely punctate, weakly shining. Genae raised, smooth, shining, without posterior ridge.

Pronotum weakly arcuate; anterior margin straight behind eyes, emarginate behind frons; PF1, PF2 and PF4 absent; PF3 shallow.

Elytra weakly arcuate laterally; summit of posterior declivity near midlength; lateral explanate margins narrow; serial punctures small, round, separated by ca. 2xpd, slightly larger than pronotal punctures. Intervals not raised, shining, ca. 2xpd. Apices in dorsal aspect conjointly rounded, in posterior aspect margins not forming angle with one another.

Ratios of P2 width and plaque shape (P2/w/l/s) ca. 1/2/5/2. P1 laminate; median carina sinuate in profile. P2 very narrow, almost laminate, l/w ca. 3/1, sides parallel, blunt apex raised slightly above mesoventral intercoxal process. Plaques small, oval, margins indistinct, not raised, located at sides of very shallow median depression. AIS width at slightly arcuate posterior margin ca. 3x P2. Protibia slightly arcuate. Mesotibia straight. Metatibia very slightly arcuate, distal ½ of medial margin emarginate and with small brush of setae in unilinear row. Abdominal apex with apicomedian notch.

Etymology. Named in reference to the very narrow prosternal intercoxal process.