Hydraena amplexa, Perkins, 2017

Perkins, Philip D., 2017, Hydraenidae of Madagascar (Insecta: Coleoptera), Zootaxa 4342 (1), pp. 1-264 : 57-58

Hydraena amplexa , new species

Figs. 46 (habitus), 48 (aedeagus), 249 (map)

Type Material. Holotype (male): Fianarantsoa, Andringitra NP, route to Haut Plateau, small helocrene in Ericacean brush forest, elev. 1814 m, 22° 8' S, 46° 53' E, 12 iv 2011, R. Gerecke (MD 199) ( NMW,) . Paratypes (40): Same data as holotype (9 NMW); Antananarivo, 18.4133S 47.9443E Analamanga, 10km E of Anjozorobe, Anjozorobe forest reserve, forest stream next to Saha forest camp, elev. 1240 m, 18° 24' S, 47° 56' E, 23 xi 2014, J. Bergsten, R. Bukontaite, J.H. Randriamihaja, T. Ranarilalatiana & S. Holmgren ( MAD14-77 ) (2 NHRS); Fianarantsoa, Andringitra NP, (Fianarantsoa), ca . 300 m W Cascade du Roi , swamp near irrigation channel, elev. 1725 m, 22° 8' S, 46° 53' E, 14 iv 2011, R. Gerecke (MD 209) (9 NMW); Andringitra NP, (Fianarantsoa), R. Amboahisy, right riparian springs above bridge at lower campsite, elev. 1571 m, 22° 8' S, 46° 53' E, 13 iv 2011, R. Gerecke (MD 205) (17 NMW); Ranomafana N. P., sifting, elev. 1079 m, 21° 14' S, 47° 24' E, 16–18 xi 2010, P. Banar (3 MMBC).

Differential Diagnosis. Males are immediately differentiated from other species by the markedly arcuate mesotibiae, which have the distal 0.5 widened, subapically deeply notched and bearing ca. 2–3 short stout spines. The aedeagus is also unusual in the shapes of the distal part of the main piece and the apex of the paramere.

Description. Size: holotype (length/width, mm): body (length to elytral apices) 1.93/0.83; head width 0.44; pronotum 0.44/0.59, PA 0.50, PB 0.52; elytra 1.22/0.83.

Dorsum brown to dark brown, frons darkest, pronotum with margins lighter than remainder; legs brown; maxillary palpi light brown to testaceous, distal ½ of last palpomere not darker.

Head with clypeus finely sparsely punctate, disc interstices shining, lateral areas microreticulate, dull; frons punctures larger and slightly denser, discal interstices ca. 1–4xpd, shining. Pronotum moderately finely punctate; punctures in anterior and posterior 1/3 slightly larger than those of head, interstices ca. 1xpd; disc punctures much sparser and smaller, interstices ca. 2–4xpd, shining. Mentum very sparsely very finely punctulate, microreticulate, dull; postmentum microreticulate in shallow median depression, dull, lateral areas shining. Genae raised, shining, with well demarcated posterior ridge, interrupted in midline.

Pronotum arcuate laterally; anterior margin straight behind eyes, emarginate behind frons; PF1 absent; PF2 very shallow; PF3 deep; PF4 shallow.

Elytra weakly arcuate laterally; posterior declivity steep, summit near midlength; elytra convex in posterior 0.5; lateral explanate margins moderately wide; serial punctures slightly smaller than largest pronotal punctures, slightly rectangular, anterior margin of each with minute granule. Intervals not raised, shining, ca. 1–2xpd, as are interstices between punctures in row. Apices in dorsal aspect conjointly rounded, in posterior aspect margins forming very shallow if any angle with one another.

Ratios of P2 width and plaque shape (P2/w/l/s) ca. 1/1/2.5/1. P1 slightly narrower than P2; median carina weakly sinuate in profile. P2 l/w ca. 2–3/1, sides parallel, apex blunt and at same level as anteromedian carina of metaventrite. Plaques moderately large, tapering and converging anteriorly, very narrowly separated anteriorly, roundly raised, located at sides of median oval depression. Metaventrite anteromedian carina slightly shorter than plaques, terminating between anterior extremes of plaques; long longitudinal ridge on each side, extended posteriorly from margin of each mesocoxal cavity to slightly past midlength of metaventrite. AIS width at slightly arcuate posterior margin ca. 2x P2. Protibia very weakly arcuate, moderately slender. Mesotibia markedly arcuate, distal 0.5 widened, subapically deeply notched and bearing ca. 2–3 short stout spines. Metatibia very slightly arcuate, slender. Metafemur lateral margin arcuate, medial margin bisinuate. Fifth ventrite with large sublateral smooth tumidities between which large, dense brush of setae. Abdominal apex with very small apicomedian notch.

Etymology. Named in reference to the markedly arcuate mesotibiae.