Hydraena dilutipoides, Perkins, 2017

Perkins, Philip D., 2017, Hydraenidae of Madagascar (Insecta: Coleoptera), Zootaxa 4342 (1), pp. 1-264 : 112-115

Hydraena dilutipoides , new species

Figs. 99 (habitus), 102 (aedeagus), 276 (map)

Type Material. Holotype (male): Mahajanga, Parc National Tsingy de Bemaraha, 2.5 km 62° ENE Bekopaka, Ankidrodroa River, sifted litter, tropical dry forest on Tsingy, elev. 100 m, 19° 7' S, 44° 48' E, 11–15 xi 2001, Fisher, Griswold et al. (BLF 4340) ( CAS) Paratypes (6): Same data as holotype (4 CAS); Mahajanga, Parc National Tsingy de Bemaraha, 3.4 km 93° E Bekopaka, Tombeau Vazimba, sifted litter, tropical dry forest, elev. 50 m, 19° 8' S, 44° 49' E, 6–10 xi 2001, Fisher, Griswold et al. (BLF 4232) (2 CAS).

Differential Diagnosis. Based on the aedeagi, closely related to H. dilutipes , differing therefrom by the smaller size (ca. 1.73 mm vs. 1.81), the less densely punctate pronotum, the larger elytral punctures, and having the elytra intervals not strongly raised and not forming unbroken lines. The plaques of H. dilutipoides are more widely separated, especially posteriorly, and the elytral intervals are not as uniformly raised. Males of both species have large metatibial brushes. The aedeagi also show a relationship, having a large, flat distal extension of the main piece; the complex gonopore bearing distal piece differs significantly in the two species ( Figs. 100–102).

Description. Size: holotype (length/width, mm): body (length to elytral apices) 1.73/0.74; head width 0.44; pronotum 0.40/0.57, PA 0.45, PB 0.50; elytra 1.08/0.74. Dorsum dark brown, head darkest; legs brown; maxillary palpi brown to light brown, distal ½ of last palpomere darker.

Head and pronotum densely moderately coarsely punctate, punctures of pronotum larger than those of head, each puncture with very short recumbent seta; interstices varying from narrow ridges anteriorly and posteriorly to ca. 2xpd on disc, shining. Mentum sparsely finely punctulate, shining; postmentum rugulose, dull. Genae raised, weakly rugulose, dull, with posterior ridge, shining medially.

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 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. Intervals very weakly raised, not forming distinct unbroken lines, shining, ca. 1xpd. Apices in dorsal aspect conjointly rounded, in posterior aspect margins forming shallow angle with one another.

Ratios of P2 width and plaque shape (P2/w/l/s) ca. 1/1/2/1.3. P1 laminate; median carina sinuate in profile. P2 l/w ca. 2/1, sides parallel or slightly converging to blunt apex, apex raised slightly above mesoventral intercoxal process. Plaques large, 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 slightly arcuate posterior margin ca. 2x P2. Protibia moderately wide, slightly arcuate on medial margin, slightly more so on lateral margin. Mesotibia straight. Metatibia slightly arcuate, distal ½ of medial margin emarginate and with large brush of setae. Abdominal apex symmetrical, last tergite with deep and rather wide apicomedian notch.

Etymology. Named in reference to the relationship to H. dilutipes .