Hydraena thumbelipes, 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 : 30-31

Hydraena thumbelipes , new species

( Figs. 30 , 32 , 286–291 , 441 )

Type Material. Holotype (male): Sandaun Province: Mianmin , river, elev. 990 m, 4° 54.57' S, 141° 35.49' E, 23 x 2008, S. Ibalim ( PNG 192) ( ZSM) . Paratypes (94): Eastern Highlands Province: Akameku– Brahmin , Bismarck Range, elev. 700 m, 5° 52.754' S, 145° 23.209' E, 24 xi 2006, Balke & Kinibel ( PNG 109) (1 ZSM) ; Madang Province: Aiome area , elev. 130 m, 5° 10.593' S, 144° 42.8' E, 11 iii 2007, Kinibel ( PNG 156) (16 MCZ, NHM, NMW, PNG, ZSM) ; Finisterre Mts. , Lower Naho Valley, Hinggia, ex rocks and gravel bank of swift clear stream, elev. 762 m, 5° 50' S, 146° 7' E, 28 xi 1964, M. E. Bacchus (MEB 112) (28 NHM) ; Finisterre Mts. , Naho River Valley, Budemu, ex gravel banks of large river, elev. 1264 m, 5° 56' S, 146° 40' E, 18 x 1964, M. E. Bacchus (MEB 61) (4 NHM) ; Finisterre Mts. , Naho River Valley, Damanti, ex gravel banks of small fast river, elev. 1082 m, 5° 55' S, 145° 58' E, 8 x 1964, M. E. Bacchus (MEB 37) (17 NHM) ; Sandaun Province: May River , ex river side pool, elev. 970 m, 4° 49.779' S, 141° 38.174' E, 19 x 2003, K. Sagata (WB 41) (3 ZSM) ; Mianmin , elev. 670 m, 4° 53.292' S, 141° 34.118' E, 20 x 2008, S. Ibalim ( PNG 191) (1 ZSM) ; Mianmin elev. 670 m, 4° 53.329' S, 141° 35.263' E, 22 x 2008, S. Ibalim ( PNG 189) (3 ZSM) ; Mianmin , river, elev. 700 m, 4° 52.858' S, 141° 31.706' E, 21 x 2008, S. Ibalim ( PNG 197) (2 ZSM) ; Mianmin , elev. 990 m, 4° 54.57' S, 141° 35.49' E, 23 x 2008, S. Ibalim ( PNG 192) (17 MCZ, NHM, NMW, PNG, ZSM) ; Mianmin , elev. 1080 m, 4° 55.78' S, 141° 38.185' E, 24 x 2008, S. Ibalim ( PNG 195) (3 ZSM) .

Differential Diagnosis. Very similar to H. thumbelina in habitus, size, shape of the metaventral plaques, and shape of the male protibia ( Figs. 27 , 30 , 286–287 ). Hydraena thumbelipes is shorter but as wide as H. thumbelina (ca. 1.29/0.53 vs. 1.40/0.53). The shapes of the male metatibiae differ in the two species: in H. thumbelipes the metatibia is expanded subapically (SEM Fig. 291 ), whereas in H. thumbelina the metatibia is weakly sinuate on the medial margin ( Fig. 27 ). Reliable determinations will also be based on close examination of the quite similar male genitalia ( Figs. 29 , 32 ). The metaventrite, abdominal apex, and very complicated chaetotaxy of the male tibiae are illustrated with SEMs ( Figs. 286–291 ).

Description. Size: holotype (length/width, mm): body (length to elytral apices) 1.29/0.53; head 0.21/0.33; pronotum 0.31/0.39, PA 0.34, PB 0.32; elytra 0.76/0.53. Dorsum of head piceous; pronotum dark brown to piceous except light brown to testaceous band across anterior border, ratios of color bands, as measured in midline, ca. 4/ 17; elytra dark brown; legs and maxillary palpi light brown, tip of palpus not darker.

Frons punctures ca. 1–2xef, slightly larger near eyes than medially; interstices shining, 1–6xpd. Clypeus microreticulate laterally, very finely sparsely punctate medially. Mentum very sparsely very finely punctulate, shining; postmentum micropunctulate. Genae raised, shining, without posterior ridge. Pronotum cordiform, median 1/2 of anterior margin emarginate; punctures on disc ca. 1xpd those of frons, interstices shining, 1–4xpd, 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 at or very near 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, a few punctures subserial. 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. 3/2.5/9/2. P1 laminate; median carina sinuate in profile. P2 raised, l/w ca. 5/3, sides converging toward blunt apex. Plaques large, narrowly separated, more narrowly so at posterior than at anterior, weakly raised, each plaque slightly tapering from posterior to anterior. Metaventrite without midlongitudinal ridge. AIS width at straight posterior margin slightly greater than P2. All legs moderately long and slender. Profemur (male) with tubercle next to trochanter; protibia very slightly, if at all, arcuate, medial margin widened in distal 1/3, apex with cluster of short spines. Mesotibia very slightly arcuate. Metatibia distal 1/3 slightly widened on medial margin. Abdominal apex symmetrical, sclerites fused, densely setose; last tergite (male) notched. Aedeagus as illustrated ( Fig. 32 ).

Etymology. Named in reference to the modified metatibiae and the relationship to H. thumbelina .

Distribution. Currently known from Areas 2 and 5; records seem to track Area 2 rather well; elevation range 130–1264 m, with only one of eleven records above 1100 m ( Fig. 441 ).

Figures

FIGURE 27. Hydraena thumbelina, holotype, dorsal and lateral habitus, and venter.

FIGURE 30. Hydraena thumbelipes, holotype, dorsal and lateral habitus, and venter.

FIGURES 32–33. Aedeagi of holotypes. 32. H. thumbelipes. 33. H. phainops.

FIGURES 286–291. Scanning electron micrographs of H. thumbelipes.

FIGURES 439–442. Geographical distributions of Hydraena species.

FIGURES 28–29. Aedeagi of holotypes. 28. H. sepikramuensis. 29. H. thumbelina.