Hydraena pilotumida, Perkins, 2017

Perkins, Philip D., 2017, Hydraenidae of Madagascar (Insecta: Coleoptera), Zootaxa 4342 (1), pp. 1-264 : 116

Hydraena pilotumida , new species

Figs. 103 (habitus), 105 (aedeagus), 277 (map)

Type Material. Holotype (male): Fianarantsoa, 7 km W Ranomafana , from seepage over sunlit rock at river, montane rainforest, elev. 900 m, 21° 16' S, 47° 25' E, 6 ix 1993, W. E. Steiner & M. Stebbins ( USNM) . Paratypes (94): Same data as holotype (5 USNM); Same data except W. E. Steiner & J. E. Cadle (6 USNM) ; Fianarantsoa, 7 km W Ranomafana, on seepage over exposed rocks at bank of Namorona River , elev. 900 m, 21° 16' S, 47° 25' E, 1–7 iii 1990, W. E. Steiner (10 USNM) ; Namorona River, 7 km W Ranomafana , from semi-shaded temporary pond in montane rain forest, elev. 1100 m, 21° 15' S, 47° 25' E, 8–21 x 1988, W. E. Steiner (5 USNM) ; Namorona River, 7 km W Ranomafana, on seepage over exposed rock at bank of Namorona River , elev. 900 m, 21° 16' S, 47° 25' E, 1–7 xi 1988, W. E. Steiner (2 USNM); Ranomafana, Sakaroa R., Cascade Riana, elev. 994 m, 21° 16' S, 47° 25' E, 1 xi–30 xii 2004, M. Balke (MD 030) (15 ZSMC); Vatovavy-Fitovinany, Ranomafana NP, Shakaroa waterfall, 2km from park entrance, 21.2631S, 47.4132E, waterfall and hygropetric rock with some dead leaves, 21° 16' S, 47° 25' E, 4 xi 2014, P. D. Perkins ( MAD14-13 ) (1 MCZ) ; Toamasina, 18.8282S 48.4398E Alaotra Mangoro Andasibe- Mantadia NP, Mantadia waterfall Beanamalao , 7km N of park entrance "circuit chute sacre", waterfall with hygropetric rocks, elev. 990 m, 18° 49' S, 48° 26' E, 28 xi 2014, J. Bergsten, R. Bukontaite, J.H. Randriamihaja, T. Ranarilalatiana & S. Holmgren ( MAD14-84 ) (50 NHRS).

Differential Diagnosis. One of the larger members of the group (ca. 2.02 mm). Males differentiated from others by the form of the metatibiae: slightly arcuate, medial margin with a large brush of setae that begins slightly before midlength and continues almost to the apex. The habitus is similar to that of H. pilobova , but the male metatibiae and the sixth ventrite differ in the two species. The aedeagi also show a relationship, but differ in shapes of several parts ( Figs. 105, 106).

Description. Size: holotype (length/width, mm): body (length to elytral apices) 2.02/0.84; head width 0.47; pronotum 0.48/0.60, PA 0.47, PB 0.53; elytra 1.29/0.84.

Dorsum dark brown, head darkest; legs brown to dark brown; maxillary palpi brown to light brown, distal ½ of last palpomere darker.

Head and pronotum densely moderately coarsely punctate. Pronotal punctures larger than those of head; interstices varying from narrow ridges anteriorly and posteriorly to ca. 1xpd on disc, shining. Mentum sparsely moderately finely punctulate, very weakly shining; postmentum rugulose, dull. Genae roundly raised, smooth and shining, without posterior ridge.

Pronotum bisinuate laterally, distinctly emarginate between anterior angle and widest part of pronotum; anterior margin straight behind eyes, emarginate behind frons; PF1 very shallow; PF2 shallow, very shallowly confluent medially forming very weak U-shaped impression; PF3 moderately deep; PF4 very shallow, nearly absent.

Elytra weakly arcuate laterally; summit of posterior declivity near distal 2/3; lateral explanate margins moderately narrow; serial punctures round, separated by ca. 1xpd, slightly larger than pronotal punctures, some punctures random near scutellum. Intervals very weakly raised, not forming distinct unbroken straight lines, shining, ca. 1xpd. Apices in dorsal aspect broadly conjointly rounded, in posterior aspect margins forming moderately deep angle with one another.

Ratios of P2 width and plaque shape (P2/w/l/s) ca. 1/1.5/2.2/1. P1 laminate; median carina sinuate in profile. P2 l/w ca. 2/1, sides parallel, apex blunt and raised slightly above metaventral intercoxal process. Plaques large, narrowly separated, widest at anterior 1/3, anteriorly and posteriorly rounded, more sharply so posteriorly, converging slightly anteriorly, not raised, located at sides of median depression. Metaventrite with very short longitudinal ridge on each side, extended posteriorly from margin of each mesocoxal cavity. AIS width at arcuate posterior margin ca. 2x P2. Protibia very weakly arcuate, almost straight, slightly widened at ca. distal ¼ and here bearing on medial surface row of short spines, one larger than the others. Mesotibia straight. Metatibia slightly arcuate, medial margin with large brush of setae that begins slightly anterior to midlength and continues almost to apex. Metafemur lateral margin strongly arcuate, medial margin strongly sinuate.

Abdominal apex with deep apicomedian concavity, upper margin bearing short setae and lower margin asymmetrical, with small produced point off center. Ventrite 6 with pair of low submedian tumidities that bear short setae.

Etymology. Named in reference to the pubescent tumidities of abdominal ventrite six.