Hydraena fenestella, 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 : 143

Hydraena fenestella , new species

( Figs. 266 , 268 , 364–368 , 418 , 549 )

Type Material. Holotype (male): Morobe Province: Lae–Bulolo road, ex dead leaves on mud bank, [GE est.] 900–1100 m, 6° 52' S, 146° 37' E, 28 xii 1964, M. E. Bacchus (MEB 123) ( NHM) . Paratypes (75): Morobe Province: Same data as holotype (74 NHM); Huon Pen., road to Kwapsanek, 250 m, 6° 30.27' S, 146° 59.581' E, 31 iii 2006, Balke & Sagata ( PNG 24) (1 ZSM) .

Differential Diagnosis. Very similar in dorsal habitus and ventral structures to H. herzogestella , the other member of the Fenestella group ( Figs. 266 , 267 ); differing therefrom in smaller size (ca. 1.22 vs. 1.32 mm) and in plaque ratios (ca. 5/1.5/5/4 vs. 6/1/6/5). Reliable determinations will require careful examination of the male genitalia ( Figs. 268, 269 ). The meso- and metaventrite, pronotum, and very complicated chaetotaxy of the protibiae are illustrated with SEMs ( Figs. 364–368 ).

Description. Size: holotype (length/width, mm): body (length to elytral apices) 1.22/0.58; head 0.20/0.32; pronotum 0.32/0.47, PA 0.36, PB 0.47; elytra 0.72/0.58. Dorsum of head with frons brown, clypeus and labrum testaceous; pronotum testaceous, semi-transparent; elytra brown; legs light brown to testaceous; maxillary palpi testaceous, tip not darker. Dorsum shining.

Frons punctures ca. 1xef near eyes, smaller and much sparser medially; interstices shining, 1–2xpd laterally, ca. 4–6xpd medially. Clypeus effacedly microreticulate laterally, very finely sparsely punctulate medially. Mentum very sparsely very finely punctulate, shining. Postmentum anteriorly finely punctate, posteriorly moderately coarsely punctate, shining. Genae flat or very slightly raised, shining, without posterior ridge. Pronotum subtrapezoidal, ca. median 3/4 of anterior margin slightly arcuate to posterior, side very slightly emarginate between anterior angle and midlength; punctures on disc ca. 1xpd of largest frons punctures, interstices strongly shining, ca. 1– 4xpd; PF1, PF2 and PF4 absent; PF3 shallow.

Elytra with posterior declivity very gradual, summit slightly anterior to midlength; lateral explanate margins narrow. Punctures very small, shallow, ca. 1xpd pronotal punctures, and widely spaced. Intervals shining, ca. 3– 5xpd or greater. 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. 5/1.5/5/4. P1 ca. 1/3 P2; median carina nearly straight in profile, very slightly arcuate between coxae. P2 markedly concave, length ca. equal width, sides slightly converging toward blunt apex. Plaques roundly slightly raised, converging but not joining anteriorly, at sides of inverted Vshaped median depression. Metaventrite conjointly concave with P2 between mesocoxae. AIS width at straight posterior margin ca. equal P2. All legs of moderate length, tibiae very slender. Profemur (male) without tubercle next to trochanter; protibia arcuate, especially in basal 1/2, gradually increasing in width from base to distal 1/3, then slightly narrowing to apex. Meso- and metatibia straight. Abdominal apex symmetrical; last tergite (male) sharply rounded. Aedeagus as illustrated ( Fig. 268 ).Female tergite X, gonocoxite, and spermatheca as illustrated ( Fig. 418 ).

Etymology. "Little window"; named in reference to the transparency of the pronotum.

Distribution. Currently known only from two localities somewhat near Lea; one at the eastern extreme of Area 3 (900–1100 m), and one on the southern part of the Huon Peninsula (250 m) ( Fig. 549 ).

Figures

FIGURE 266. Hydraena fenestella, holotype, dorsal and lateral habitus, and venter.

FIGURE 267. Hydraena herzogestella, holotype, dorsal and lateral habitus, and venter.

FIGURES 268–269. Aedeagi of holotypes. 268. H. fenestella. 269. H. herzogestella.

FIGURES 364–369. Scanning electron micrographs of H. fenestella (364–368) and H. remulipes (369).

FIGURES 416–419. Female tergite X, gonocoxite, and spermatheca of Hydraena species.

FIGURES 547–550. Geographical distributions of Hydraena species.