Hydraena okapa, 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 : 73-74

Hydraena okapa , new species

( Figs. 119 , 121 , 324–327 , 401 , 483 )

Type Material. Holotype (male): Eastern Highlands Province: Wanitabi Valley, nr. Okapa , gravel banks of small swift river, 1372 m, 6° 32' S, 145° 37' E, 5 ii 1965, M. E. Bacchus (MEB 171a) ( NHM) . Paratypes (96): Eastern Highlands Province: Wanitabi Valley, nr. Okapa , ex dead leaves caught among rocks in small swift river, 1372 m, 6° 32' S, 145° 37' E, 5 ii 1965, M. E. Bacchus (MEB 171b) (11 NHM) ; Wanitabi Valley, nr. Okapa , gravel banks of small swift river, 1372 m, 6° 32' S, 145° 37' E, 5 ii 1965, M. E. Bacchus (MEB 171a) (71 NHM) ; Wanitabi Valley, nr. Okapa , on wet rocks above waterline in small swift river, 1372 m, 6° 32' S, 145° 37' E, 5 ii 1965, M. E. Bacchus (MEB 171c) (14 NHM) .

Differential Diagnosis. A moderately sized, darkly colored species with sexually dimorphic legs (SEM Figs. 325–327 ). Bearing some superficial similarity in habitus to H. fascinata ( Figs. 119 , 122 ); differentiated therefrom by the very different leg structure and very different aedeagi ( Figs. 121 , 124). The female tergite X, gonocoxite and spermatheca are very different in the two species ( Figs. 401, 402 ). The plaques are unusual in that the medial margins are closer to one another in the middle than at either end. The aedeagus ( Fig. 121 ) has unusual parameres. The metaventrite, abdominal apex, and very complicated chaetotaxy of the tibiae are illustrated with SEMs ( Figs. 324– 327 ).

Description. Size: holotype (length/width, mm): body (length to elytral apices) 1.75/0.72; head 0.25/0.40; pronotum 0.42/0.50, PA 0.43, PB 0.42; elytra 1.08/0.72. Dorsum piceous; legs and maxillary palpi dark brown.

Frons moderately fine, moderately densely punctate, punctures ca. 1xef; interstices weakly shining, effacedly microreticulate, 1–4xpd, punctures sparser on disc. Clypeus microreticulate laterally, finely, sparsely punctate medially. Mentum very sparsely very finely punctulate, strongly shining, each puncture with moderately long recumbent seta; postmentum medially effacedly micropunctulate, otherwise finely sparsely punctate, shining. Genae raised, shining, without posterior ridge.

Pronotum weakly cordiform, median 2/3 of anterior margin straight or very weakly emarginate; punctures on disc ca. 1xpd largest punctures of frons, interstices effacedly microreticulate, dull, 1–2xpd, punctures slightly larger and denser at anterior and posterior; PF1 very shallow; PF2 moderately shallow, very shallowly confluent; PF3 deep; PF4 shallow.

Elytra with summit of posterior declivity slightly past midlength; lateral explanate moderately wide; on basal 1/3 punctures ca. 1xpd largest pronotal punctures, punctures becoming gradually smaller toward posterior. Intervals not raised, effacedly microreticulate, dull or very weakly 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 shallow angle with one another.

Ratios of P2 width and plaque shape (P2/w/l/s) ca. 3/4/11/3. P1 laminate; median carina sinuate in profile. P2 raised, l/w ca. 8/3, sides slightly converging toward apex. Plaques wide, flat, closely spaced, medial margins converging slightly toward one another at midlength, located at sides of median depression. Metaventrite without midlongitudinal ridge. AIS width at straight posterior margin ca. 2x P2. Middle and hind legs long and slender, front legs more robust. Profemur (male) with tubercle near trochanter; protibia very slightly arcuate, distal 1/3 widened on medial margin and bearing row of very short spines. Mesotibia very slightly arcuate, medial surface subapically notched. Metatibia straight, medial margin very slightly widened at ca. distal 1/3. Abdominal apex symmetrical; last tergite (male) deeply notched. Aedeagus as illustrated ( Fig. 119 ).

Female tergite X, gonocoxite, and spermatheca as illustrated ( Fig. 401 ).

Etymology. Named in reference to the geographical locality.

Distribution. Currently known only from the type locality near Okapa, in eastern Area 1; elevation 1372 m ( Fig. 483 ).

Note. In some specimens the medial margins of the plaques are more nearly parallel than they are in the holotype ( Fig. 119 ).

Figures

FIGURE 119. Hydraena okapa, holotype, dorsal and lateral habitus, and venter.

FIGURE 122. Hydraena fascinata, holotype, dorsal and lateral habitus, and venter.

FIGURES 120–121. Aedeagi of holotypes. 120. H. idema. 121. H. okapa.

FIGURES 322–327. Scanning electron micrographs of H. phainops (322–323) and H. okapa (324–327).

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

FIGURES 483–486. Geographical distributions of Hydraena species.