Hydraena acicula, Perkins, 2017

Perkins, Philip D., 2017, Hydraenidae of Madagascar (Insecta: Coleoptera), Zootaxa 4342 (1), pp. 1-264 : 48-49

Hydraena acicula , new species

Figs. 37 (habitus), 40 (aedeagus), 244 (map)

Type Material. Holotype (male): Antsiranana, Antsaba, Galoko Mountains , hygropetric cascade, elev. 303 m, 13° 39' S, 48° 45' E, 1 xi–29 xii 2004, M. Balke (MD 016) ( ZSMC) . Paratypes (15): Same data as holotype (13); Antsiranana, Anjiabe Ambony: Ambilobe : Antsabe stairways-like cascade with vertical (!) steps, exposed, extremely hot day, N: - 13.60930 E: 48.72120, elev. 303 m, 13° 37' S, 48° 43' E, 23 xi 2004, Balke et al. (P25MD16) (1 ZSMC); Antsaba, Galoko Mountains , hygropetric cascade, elev. 303 m, 13° 39' S, 48° 45' E, 1 xi–29 xii 2004, M. Balke (MD 016) (13 ZSMC); Forêt d' Antsahabe, 11.4 km 275° W Daraina, sifted litter (leaf mold, rotten wood) tropical dry forest, elev. 550 m, 13° 12' S, 49° 33' E, 12 xii 2003, B.L.Fisher (BLF 10116) (1 CAS).

Differential Diagnosis. Similar in habitus to H. antsahabe ; also similar in size, shape and separation of the metaventral plaques; slightly smaller than H. antsahabe in body size (ca. 1.22 vs. 1.37 mm). Reliable determinations will require dissection of males; the aedeagi differ distinctively in shapes of both the main piece and the paramere ( Figs. 39, 40).

Description. Size: holotype (length/width, mm): body (length to elytral apices) 1.22/0.52; head width 0.33; pronotum 0.30/0.41, PA 0.36, PB 0.37; elytra 0.73/0.52.

Dorsum with head dark brown; pronotum with brown diffusely margined macula, surrounding area light brown; elytra brown; legs light brown to testaceous; maxillary palpi testaceous, distal ½ of last palpomere not darker.

Head with clypeus finely sparsely punctate and microreticulate, dull; frons punctures much larger, interstices 0.5–2xpd, shining. Pronotum densely moderately coarsely punctate; punctures in anterior and posterior 1/3 larger than those of head, interstices narrow walls to 0.5xpd; disc punctures sparser, interstices ca. 0.5xpd, shining. Mentum sparsely finely punctulate, microreticulate, dull; postmentum microreticulate in shallow median depression, dull, lateral areas shining. Genae raised, shining, with weakly demarcated posterior ridge, interrupted in middle.

Pronotum arcuate laterally; 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 moderately narrow; serial punctures slightly rectangular, each with minute granule at anterior margin, ca. 0.5– 1xpd. Intervals not raised, weakly shining, ca. 0.5–1xpd. Apices in dorsal aspect conjointly rather sharply rounded, in posterior aspect margins forming very shallow angle with one another.

Ratios of P2 width and plaque shape (P2/w/l/s) ca. 1/1/3/1. P1 almost as wide as P2; median carina weakly sinuate in profile. P2 l/w ca. 2/1, sides parallel, apex blunt and at same level as anteromedian carina of metaventrite. Plaques very large, elongate oval, parallel, narrowly separated, slightly raised, located at sides of narrow median depression. Metaventrite anteromedian carina slightly shorter than plaques, terminating just slightly anterior to anterior extreme of plaques; long longitudinal ridge on each side, extended posteriorly from margin of each mesocoxal cavity to ca. midlength of metaventrite. AIS width at slightly arcuate posterior margin ca. 1.5x P2. Protibia very weakly arcuate, almost straight, moderately wide. Mesotibia straight, stout, widest near midlength; medial margin subapically with 4–5 short stout spines, margin notched between spines. Metatibia straight. Metafemur lateral margin weakly arcuate, medial margin weakly bisinuate. Abdominal apex with very small apicomedian notch.

Etymology. Named in reference to the sharply pointed paramere.