Hydraena gereckei, Perkins, 2017

Perkins, Philip D., 2017, Hydraenidae of Madagascar (Insecta: Coleoptera), Zootaxa 4342 (1), pp. 1-264 : 101-102

Hydraena gereckei , new species

Figs. 90 (habitus), 92 (aedeagus), 271 (map)

Type Material. Holotype (male): Antananarivo, 109, 0 8.10.2001 Ankaratra, Reserve Manjakatompo, riparian spring exp. SE at spring stream N deviation to Analamitana (site MD 108), elev. 1850 m, 19° 25' S, 47° 12' E, 8 x 2001, Gerecke & Goldschmidt (MD 109) ( NMW) . Paratypes (6): Same data as holotype (5 NMW). Antananarivo, Ankaratra (Antananarivo), Reserve Manjakatompo , ripar. spring at left branch of affluent to piscicole, elev. 1770 m, 19° 21' S, 47° 18' E, 9 x 2001, Gerecke & Goldschmidt (MD 110d) (1 NMW).

Differential Diagnosis. Very similar in habitus and large size (ca. 2.20 mm) to H. manjakatompo ; both species have relatively small pronota compared to the size of the elytra. Reliable determinations will require dissection of males. The aedeagi clearly show a relationship, but differ in shapes of the distal part of the main piece, and its orientation compared to the basal orifice ( Figs. 92, 95).

Description. Size: holotype (length/width, mm): body (length to elytral apices) 2.18/0.96; head width 0.46; pronotum 0.45/0.71, PA 0.54, PB 0.61; elytra 1.39/0.96.

Dorsum dark brown; elytral epipleurs slightly lighter than remainder of elytra, and lighter than venter; legs dark brown; maxillary palpi light brown, distal ½ of last palpomere not darker.

Head with clypeus finely moderately sparsely punctate, interstices microreticulate laterally; frons more coarsely punctate laterally than medially where interstices ca. 0.5–1xpd. Pronotum in anterior and posterior 1/3 moderately coarsely densely punctate, interstices narrow walls to 1xpd; punctures on disc distinctly smaller, interstices ca. 1–2xpd, shining. Mentum microreticulate, dull; postmentum microreticulate medially. Genae raised, shining, with posterior ridge, interrupted in midline.

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

Elytra weakly arcuate laterally; summit of posterior declivity slightly before midlength; lateral explanate margins wide; serial punctures slightly rectangular, each with minute granule at anterior margin, separated by ca. 1xpd, slightly smaller than largest pronotal punctures. Intervals not raised, shining, ca. 1.5x puncture width. 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. 1/1.5/2.5/1. P1 slightly narrower than P2; median carina weakly sinuate in profile. P2 l/w ca. 2/1, sides parallel, apex blunt and on same level as anteromedian carina of metaventrite. Plaques subtriangular, narrowing and slightly converging anteriorly, separated basally by ca. 1x plaque width, very slightly raised, located at sides of median depression. Metaventrite anteromedian carina ca. as long as plaques, not quite 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. 1.5x P2. Protibia medial margin straight, lateral margin very weakly arcuate. Mesotibia arcuate, widest near midlength, medial margin with 4 or 5 short sharp spines, surface of tibia notched between spines, spines longer and stronger from most proximal to most distal. Metatibia very weakly arcuate, slender. Metafemur more strongly arcuate on lateral than medial margin. Abdominal apex with narrow apicomedian notch.

Etymology. Named in honor of the collector, Reinhard Gerecke.

Remarks. The maxillary palpi of this species are comparatively short, ca. 0.61 mm, whereas in other species of about the same body length the palpi average about 0.75 mm. The shortening appears to principally be a reduction in the length of the fourth (last) palpomere, which is shorter than the second (ratios of meres 2/3/4 as 2.29/1/1.57), to a greater extent than is seen in other species.