Hydraena ibalimi, 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 : 68-69

Hydraena ibalimi , new species

( Figs. 107 , 109 , 400 , 485 )

Type Material. Holotype (male): Sandaun Province: Mianmin , river, 1080 m, 4° 55.78' S, 141° 38.185' E, 24 x 2008, S. Ibalim ( PNG 195) ( ZSM) . Paratypes: Same data as holotype (7 MCZ, NHM, NMW, PNG, ZSM) .

Differential Diagnosis. Among members of the Velvetina group, somewhat similar in habitus to H. adelbertensis ( Figs. 107 , 110 ); these two species are the only members of the Velvetina group that have metaventral plaques (they are tiny). Hydraena ibalimi differs from H. adelbertensis by the slightly larger size (ca. 1.60 vs. 1.52 mm), the decidedly less hairy dorsum, and the proportionally larger elytra that are wider posteriorly; males additionally differentiated by the differently shaped metatibiae. The aedeagi of the two species also indicate a relationship, while differing distinctively in details ( Figs. 109 , 112).

Description. Size: holotype (length/width, mm): body (length to elytral apices) 1.60/0.66; head 0.27/0.37; pronotum 0.39/0.43, PA 0.38, PB 0.33; elytra 0.94/0.66. Dorsum piceous, except light brown to testaceous band across anterior 2/7 of pronotum; legs dark brown to reddish brown; maxillary palpi light brown, tip slightly darker.

Frons very slightly concave near eyes, punctures ca. 1xef; interstices shining, 0.5–4xpd. Clypeus microreticulate laterally, sparsely punctate medially. Mentum very sparsely very finely punctulate, shining; postmentum more densely punctate, interstices shining. Genae raised, shining, without posterior ridge. Pronotum cordiform, anterior margin straight or very slightly arcuate; punctures on disc ca. 1–2xpd those of frons; interstices shining, 1–2xpd, punctures slightly larger and denser at anterior and posterior; PF1 shallow, extending in midline to about midlenth of pronotum; PF2 deep, large, oval, oblique, medially confluent, conjointly forming U-shaped impression; PF3 deep; PF4 moderately deep.

Elytra convex, summit of posterior declivity slightly anterior to 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. 1–2xpd, as are interstices between punctures of a row. Apices in dorsal aspect conjointly rounded, in posterior aspect margins forming very shallow angle with one another.

Ratios of P2 width and plaque shape (P2/w/l/s) ca. 3/1/2/9. P1 laminate; median carina sinuate in profile. P2 raised, l/w ca. 5/3, sides slightly converging toward blunt apex. Plaques extremely small, narrow lines, raised posteriorly in tiny point, located on sides of deep median depression, hydrofuge pubescence longest lateral to median depression. AIS width at slightly arcuate posterior margin ca. 2.5x P2. All legs long and slender. Profemur (male) without tubercle next to trochanter; protibia straight, medial margin gradually widening from base to slightly past midlength, then emarginate to apex, widest point with a few large spines, emargination with row of very short spines. Mesotibia straight. Metatibia very narrow, very slightly arcuate in distal 1/2. Abdominal apex symmetrical; last tergite (male) notched. Aedeagus as illustrated ( Fig. 109 ). Female tergite X, gonocoxite, and spermatheca as illustrated ( Fig. 400 ).

Etymology. Named in honor of Papuan biologist Sentiko Ibalim, the collector of this and other new species of PNG Hydraena .

Distribution. Currently known only from the type locality, Mianmin, in the far western part of Area 1, near the border with Area 2; elevation 1080 m ( Fig. 485 ).

Figures

FIGURE 107. Hydraena ibalimi, holotype, dorsal and lateral habitus, and venter.

FIGURE 110. Hydraena adelbertensis, holotype, dorsal and lateral habitus, and venter.

FIGURES 108–109. Aedeagi of holotypes. 108. H. velvetina. 109. H. ibalimi.

FIGURES 400–403. Female tergite X, gonocoxite, and spermatheca of Hydraena species.

FIGURES 483–486. Geographical distributions of Hydraena species.