Hydraena penultimata, Perkins, 2011

Perkins, Philip D., 2011, New species (130) of the hyperdiverse aquatic beetle genus Hydraena Kugelann from Papua New Guinea, and a preliminary analysis of areas of endemism (Coleoptera: Hydraenidae) 2944, Zootaxa 2944 (1), pp. 1-417 : 54-55

Hydraena penultimata , new species

( Figs. 78 , 80 , 465 )

Type Material. Holotype (male): Sandaun Province: May River , ex river side pool, 970 m, 4° 49.779' S, 141° 38.174' E, 19 x 2003, K. Sagata (WB 41) ( ZSM) . Paratype: Same data as holotype (1 male ZSM) .

Differential Diagnosis. Immediately differentiated from other members of the Tetana group by the elongate, fasciate pronotum (PL/PW ca. 0.94 vs. 0.83–0.87 for other species). The metaventral plaques are narrower and more widely separated than other members of the group, except H. altapapua ( Figs. 78 , 83 ). Males are additionally recognized by the uniquely widened and flattened penultimate maxillary palpomere. The aedeagus of this species stands apart from that of other members of the Tetana group ( Fig. 80 ). This species, from far western PNG ( Fig. 465 ), might represent a species group of western NG.

Description. Size: holotype (length/width, mm): body (length to elytral apices) 1.87/0.72; head 0.28/0.40; pronotum 0.47/0.50, PA 0.44, PB 0.42; elytra 1.11/0.72. Dorsum of head piceous; pronotum with very large piceous fascia, bordered anteriorly and posteriorly by light brown to testaceous, color band ratios ca. 7/20/3, posterior band very faint; legs and maxillary palpi brown.

Frons punctures ca. 1–2xef, slightly larger near eyes than medially; interstices shining, 1–2xpd. Clypeus microreticulate laterally, very finely sparsely punctate medially. Maxillary palpus (male) with penultimate palpomere widened, ventral surface flat. Mentum very sparsely very finely punctulate, shining; postmentum densely micropunctulate medially, otherwise finely punctate and shining. Genae raised, shining, without posterior ridge. Pronotum moderately elongate, PL/PW ca. 0.94, median 2/3 of anterior margin emarginate; punctures on disc ca. 1xpd those of frons, interstices shining, 2–4xpd, punctures slightly larger and denser at anterior and posterior; PF1 absent; PF2 very shallow, obsolete; PF3 deep; PF4 absent.

Elytra with summit of posterior declivity slightly past midlength; lateral explanate margins moderately wide; on basal 1/3 punctures ca. 1xpd largest pronotal punctures, punctures becoming gradually smaller toward posterior. Intervals not raised, shining, on disc ca. 2–3xpd, as are interstices between punctures of a row, a few punctures subserial. Apices in dorsal aspect separately rounded, in posterior aspect margins forming shallow angle with one another.

Ratios of P2 width and plaque shape (P2/w/l/s) ca. 3/3/13/2. P1 laminate; median carina sinuate in profile. P2 raised, l/w ca. 2/1, sides converging toward blunt apex. Plaques very large, very narrowly separated, medial margins parallel, weakly raised. Metaventrite without midlongitudinal ridge. AIS width at straight posterior margin ca. 1.7x P2. All legs long and very slender. Profemur (male) with small, sharply pointed tubercle next to trochanter; protibia straight or very slightly arcuate, in ventral aspect gradually increasing in width from base to apex, distal 1/ 3 slightly widened on anterior surface, cluster of short spines apically on medial surface, moderately long spine on medial surface at base of widened area. Mesotibia very slightly arcuate; mesotarsi with short setae along lower margin. Metatibia straight, medial margin very weakly widened near midlength; metatarsi with long hair-like setae along lower margin of basal tarsomeres. Fifth abdominal ventrite simple. Sixth ventrite medial area flattened, on each side of which very slightly raised. Abdominal apex symmetrical; last tergite (male) deeply notched. Aedeagus as illustrated ( Fig. 80 ).

Etymology. Named in reference to the male modified penultimate maxillary palpomere.

Distribution. Currently known only from the type locality, which is at the border of Areas 1 and 2 in far western PNG; elevation 970 m ( Fig. 465 ).

Figures

FIGURE 78. Hydraena penultimata, holotype, dorsal and lateral habitus, and venter.

FIGURE 83. Hydraena altapapua, holotype, dorsal and lateral habitus, and venter.

FIGURES 80–81. Aedeagi of holotypes. 80. H. penultimata. 81. H. acumena.

FIGURES 463–466. Geographical distributions of Hydraena species.