Hydraena furcula, Perkins, 2017

Perkins, Philip D., 2017, Hydraenidae of Madagascar (Insecta: Coleoptera), Zootaxa 4342 (1), pp. 1-264 : 44-45

Hydraena furcula , new species

Figs. 33 (habitus), 35 (aedeagus), 227 (gonocoxite and spermatheca), 242 (map)

Type Material. Holotype (male): Toliara, 40 km N of Fort Dauphin, Managotry, N:-24.78611 E:46.86331, 9 iv 2007, Ranarilalatiana et al. (P67A) (NHRS). Paratypes: Same data as holotype (13 NHRS).

Differential Diagnosis. The largest member of the species group (ca. 2.57 mm), having the metaventral plaques more arcuate than other members. A dark brown species, often with the pronotal angles and elytral humeri yellowish. The maxillary palpi are comparatively long: the ratio of mx. palpi length/body length being one of the greatest at ca. 0.40 (range in general for Hydraena in this study ca. 0.22–0.41). This, in addition to the large body size, results in the longest maxillary palpi at ca. 1.02 mm. Clearly related to H. oscillata based on general structure of the aedeagus, but easily distinguished therefrom by the shapes of the paramere and distal processes, and thickness of the main piece ( Figs. 35, 36).

Description. Size: holotype (length/width, mm): body (length to elytral apices) 2.57/1.05; head width 0.57; pronotum 0.59/0.72, PA 0.63, PB 0.67; elytra 1.57/1.05.

Dorsum brown to dark brown, head darkest, marginal areas of pronotum slightly lighter as are elytral humeri; legs brown; maxillary palpi testaceous, distal 1/3 of last palpomere not darker.

Head with clypeus moderately finely and moderately densely punctate, interstices shining, lateral margins narrowly microreticulate; frons coarsely densely punctate, interstices narrow walls to 0.5–1xpd, shining. Pronotum coarsely densely and deeply punctate, interstices narrow walls to 1xpd, shining. Mentum and postmentum coarsely punctate, subrugose in places, interstices shining. Genae raised, posterior ridge well demarcated by row of punctures, interrupted in midline.

Pronotum sinuate laterally; anterior margin straight behind eyes, emarginate behind frons; PF1 and PF2 absent; PF3 deep; PF4 shallow.

Elytra weakly arcuate laterally; summit of posterior declivity slightly past midlength; lateral explanate margins moderately narrow; serial punctures round, separated by ca. 1xpd or slightly less, slightly smaller than largest pronotal punctures. Intervals very weakly if at all raised, shining, ca. 0.5–1xpd. Apices in dorsal aspect conjointly rounded, in posterior aspect margins do not form angle with one another.

Ratios of P2 width and plaque shape (P2/w/l/s [anteriorly]) ca. 1/0.5/2/1. P1 almost as wide as P2; median carina sinuate in profile. P2 l/w ca. 2/1, sides parallel, apex blunt. Plaques moderately wide basally, tapering and converging anteriorly and joining anteromedian carina forming inverted Y-shape, located at sides of deep median depression. Metaventrite anteromedian carina shorter than plaques; longitudinal ridge on each side, extended posteriorly from margin of each mesocoxal cavity to ca. midlength. AIS width at arcuate posterior margin ca. 2x P2. Protibia straight, slender. Mesotibia with ca. middle 0.3 of length slightly arcuate and here bearing 4–5 sharp stout spines, margin very shallowly if at all notched between spines. Metatibia very weakly arcuate, slender. Metafemur rather slender, slightly arcuate on lateral margin, slightly sinuate on medial margin. Abdominal apex with slightly off-center asymmetrical notch.

Etymology. "Forked prop", named in reference to the inverted Y-shape of the metaventral carinae.