Hydraena biundulata, 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 : 53-54

Hydraena biundulata , new species

( Figs. 75 , 77 , 284, 285 , 397, 468 )

Type Material. Holotype (male): Morobe Province: Lae–Bulolo road, ex stones and gravel bank of large river, [GE est.] 900–1100 m, 6° 52' S, 146° 37' E, 28 xii 1964, M. E. Bacchus (MEB 124) ( NHM) . Paratypes: Same data as holotype (11 NHM) .

Differential Diagnosis. Among members of the Tetana group, somewhat similar in habitus to H. insandalia and H. penultimata ( Figs. 74 , 75 , 78 ); differing from both compared species by the shape of the pronotum, which is more widely produced in the middle, and nearly equally sinuate in front of and behind the widest part. Additionally, the males of H. biundulata have tibiae that are shaped differently than the compared species. The male genitalia of the three species are quite distinct, with H. biundulata being more similar to H. insandalia than to H. penultimata ( Figs. 76, 77 , 80 ). The metaventrite and the chaetotaxy of the meso- and metatibiae are illustrated with SEMs ( Figs. 284, 285 ).

Description. Size: holotype (length/width, mm): body (length to elytral apices) 1.55/0.63; head 0.26/0.37; pronotum 0.40/0.48, PA 0.40, PB 0.38; elytra 0.90/0.63. Dorsum of head piceous; pronotum light brown in front of and behind piceous, diffusely margined, fascia, ratios of color bands, as measured in midline, ca. 6/15/5; elytra dark brown; legs and maxillary palpi dark brown. Dorsum moderately shining.

Frons punctures ca. 2xef near eyes, smaller and sparser medially; interstices shining, medially 3–7xpd. Clypeus effacedly microreticulate laterally, very finely sparsely punctulate and shining medially. Mentum very sparsely very finely punctulate, strongly shining. Postmentum microreticulate in shallow median depression, otherwise moderately coarsely punctate. Genae very slightly raised, shining, with shallow, obsolete anteromedian impression, without posterior ridge. Pronotum subcordiform, distinctively narrowed both in front of and behind widest area; median 2/3 of anterior margin emarginate; punctures on disc slightly smaller than largest frons punctures, interstices shining, ca. 2–5xpd, punctures anteriorly and posteriorly ca. 2xpd those on disc, and denser; PF1 absent; PF2 and PF4 very shallow; PF3 moderately deep, wide.

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

Ratios of P2 width and plaque shape (P2/w/l/s) ca. 3/3/9/4. P1 laminate; median carina sinuate in profile, slightly raised between coxae. P2 length/width ca. 5/3, transversely very slightly concave, sides very slightly diverging toward blunt apex. Plaques large, raised slightly more laterally than medially, at sloping sides of median depression, anteriorly slightly tapering and convergent; each plaque with tiny papilla slightly behind midlength. Metaventrite between mesocoxae very weakly raised in midline. AIS width at straight posterior margin ca. 1.5x P2. All legs rather long and slender. Profemur (male) with tubercle on ventral margin near trochanter; protibia arcuate, increasing in width from near base to subapically. Mesotibia slightly arcuate. Metatibia sinuate, slender except apically widened and bearing few setae. Abdominal apex very slightly asymmetrical, if at all; last tergite (male) with very small apicomedian notch. Aedeagus as illustrated ( Fig. 77 ). Female tergite X, gonocoxite, and spermatheca as illustrated ( Fig. 397).

Etymology. Named in reference to the undulating medial surface of the male metatibiae and undulating margin of the pronotum.

Distribution. Currently known only from the type locality on the Lae–Bulolo road, at the eastern end of Area 3 where it borders Area 6; elevation 900–1100 m ( Fig. 468 ).

Figures

FIGURE 74. Hydraena insandalia, holotype, dorsal and lateral habitus, and venter.

FIGURE 75. Hydraena biundulata, holotype, dorsal and lateral habitus, and venter.

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

FIGURES 76–77. Aedeagi of holotypes. 76. H. insandalia. 77. H. biundulata.

FIGURES 280–285. Scanning electron micrographs of H. manulea (280–283) and H. biundulata (284–285).

FIGURES 467–470. Geographical distributions of Hydraena species.

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