Hydraena orchisa, Perkins, 2017

Perkins, Philip D., 2017, Hydraenidae of Madagascar (Insecta: Coleoptera), Zootaxa 4342 (1), pp. 1-264 : 138-139

Hydraena orchisa , new species

Figs. 124 (habitus), 126 (aedeagus), 288 (map)

Type Material. Holotype (male): Toamasina, 18.7911S 48.4259E Alaotra Mangoro Andasibe-Mantadia NP, Mantadia 12km N of park entrance, forest pond with some vegetation, elev. 960 m, 28 xi 2014, J. Bergsten, R. Bukontaite, J.H. Randriamihaja, T. Ranarilalatiana & S. Holmgren ( MAD14-83 ) ( NHRS) . Paratypes (53): Same data as holotype (31 NHRS); Toamasina, 18.9385S 48.4219E Alaotra Mangoro Andasibe-Mantadia NP, Analamazoatra , pond 100m E from Lac Vert , shallow forest pool, elev. 940 m, 18° 56' S, 48° 25' E, 27 xi 2014, J. Bergsten, R. Bukontaite, J.H. Randriamihaja, T. Ranarilalatiana & S. Holmgren ( MAD14-15 ) (9 NHRS); 18.9386S 48.4222E Alaotra Mangoro Andasibe-Mantadia NP, Analamazoatra, pond 150m E from Lac Vert, shallow forest pool, elev. 950 m, 18° 56' S, 48° 25' E, 27 xi 2014, J. Bergsten, R. Bukontaite, J.H. Randriamihaja, T. Ranarilalatiana & S. Holmgren ( MAD14-16 ) (13 NHRS).

Differential Diagnosis. Somewhat similar to H. clavulata in size (ca. 1.52 vs. 1.48 mm), color, arcuate lateral margins of pronotum and elytra, and dorsal sculpture; differing therefrom in having proportionally larger elytra that are less acuminate apically, absence of metaventral plaques, and having slightly arcuate metatibiae. The aedeagi of the two species are roughly similar in size and placement of the parameres, and shape of the basal orifice; however, the shapes of the distal pieces differ markedly ( Figs. 125, 126).

Description. Size: holotype (length/width, mm): body (length to elytral apices) 1.52/0.68; head width 0.37; pronotum 0.36/0.52, PA 0.38, PB 0.48; elytra 0.97/0.68.

Dorsum of head with frons and clypeus dark brown to piceous; pronotum with dark brown to piceous fascia, diffusely margined, anterior and posterior borders light brown to testaceous; elytra dark brown; legs light brown; maxillary palpi testaceous, distal ½ of last palpomere not darker.

Frons punctures ca. 1–1.5xef, slightly larger and denser near eyes than medially; interstices shining, 0.5–1xpd laterally, 1–2xpd medially. Clypeus very finely sparsely punctate. Mentum sparsely finely punctulate, shining; postmentum moderately densely punctate, shining. Genae raised, smooth, shining, without posterior ridge.

Pronotum with lateral margins slightly sinuate, posterior angles very slightly acute, nearly right angles; anterior margin straight behind eyes, emarginate in middle; punctures on disc larger and deeper than those of frons, interstices strongly shining, 1–2xpd, punctures slightly larger and much denser at anterior and posterior; PF1 absent; PF2 deep, oblique, oval; PF3 deep and large; PF4 shallow; PF3 and PF4 confluent.

Elytra weakly arcuate laterally; posterior declivity near midlength; lateral explanate margins narrow; serial punctures on disc slightly smaller than largest pronotal punctures. Intervals not raised, shining, ca. 1–2xpd, as are interstices between punctures of a row. Apices in dorsal aspect conjointly rounded, in posterior aspect margins forming shallow angle with one another.

P1 laminate; median carina sinuate in profile. P2 comparatively wide, l/w ca. 1/1, sides diverging slightly, blunt apex on same level as mesoventral intercoxal process. Plaques absent. AIS width at slightly arcuate posterior margin ca. 1x P2. Pro- and mesotibia straight, slender. Metatibia very slightly arcuate in distal 1/3. Abdominal apex with slightly off-center apical notch.

Etymology. Named in reference to the orchid-like shape of the distal piece of the aedeagus.