Hydraena tetana, 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 : 49-50

Hydraena tetana , new species

( Figs. 66 , 68, 304–307 , 395, 461 )

Type Material. Holotype (male): Eastern Highlands Province: Okapa , ex muddy gravel banks of fast, clear stream, 1524 m, 6° 32' S, 145° 37' E, 9 ii 1965, M. E. Bacchus (MEB 183) ( NHM) . Paratypes (176): Eastern Highlands Province: Mjairasa, Okapa , ex stones in waterfall spray, [GE est.] 1500–1700 m, 6° 32' S, 145° 37' E, 17 iii 1965, R. W. Hornabrook (1 NMNZ) ; Okapa , ex muddy gravel banks of fast, clear stream, 1524 m, 6° 32' S, 145° 37' E, 9 ii 1965, M. E. Bacchus (MEB 183) (7 NHM) ; Okapa , gravel banks of deep fast river, 1524 m, 6° 32' S, 145° 37' E, 10 ii 1965, M. E. Bacchus (MEB 189a) (3 NHM) ; Purosa Valley, nr. Okapa , [GE est.] 1500–1700 m, 6° 32' S, 145° 37' E, 8 ii 1965, M. E. Bacchus (MEB 182) (41 NHM) ; Purosa Valley, nr. Okapa , on submerged stones, [GE est.] 1500–1700 m, 6° 32' S, 145° 37' E, 8 ii 1965, M. E. Bacchus (MEB 182a) (3 NHM) ; Umg. [=environs of] Igipinti, Korindaiop River , [GE est.] 600–1700 m, 6° 25' S, 145° 42' E, 18 vi 1979, W. G. Ullrich (3 MHNG) ; Umg. [=environs of] Kainantu, Onerunka , [GE est.] 1500–1700 m, 6° 17' S, 145° 52' E, 16 vi 1979, W. G. Ullrich (8 MHNG) ; same locality, 21 viii 1979, W. G. Ullrich (14 MHNG) ; Umg. [=environs of] Onerunka, Ramu River , [GE est.] 1500–1700 m, 6° 20' S, 145° 47' E, 13 vi 1979, W. G. Ullrich (26 MHNG) ; same locality, 20 vi 1979, W. G. Ullrich (2 MHNG) ; Wanitabi Valley, nr. Okapa , ex muddy gravel banks of small shaded stream, 1524 m, 6° 32' S, 145° 37' E, 5 ii 1965, M. E. Bacchus (MEB 177a) (24 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) (1 NHM) ; Madang Province: Finisterre Mts., Naho River Valley, Budemu , ex gravel banks of large river, 1264 m, 5° 56' S, 146° 40' E, 18 x 1964, M. E. Bacchus (MEB 61) (9 NHM) ; Finisterre Mts., Naho River Valley, Budemu , ex sand and gravel banks of small stream, but only in the 20 yards that it is permanent, 1264 m, 5° 56' S, 146° 40' E, 19 x 1964, M. E. Bacchus (MEB 62) (3 NHM) ; Finisterre Mts., Naho River Valley, Budemu –Kikipei track, ex gravel banks of small stream, 1220 m, 5° 56' S, 146° 40' E, 24 x 1964, M. E. Bacchus (MEB 74) (1 NHM) ; Finisterre Mts., Naho River Valley, Budemu –Kikipei track, ex gravel bank of small river in places where rotten leaves had accumulated, 1220 m, 5° 56' S, 146° 40' E, 24 x 1964, M. E. Bacchus (MEB 73) (5 NHM) ; Finisterre Mts., Naho River Valley, nr. Moro , ex dead leaves and muddy gravel by small stream, 1372 m, 5° 50' S, 146° 7' E, 5 xi 1964, M. E. Bacchus (MEB 88) (15 NHM) ; Finisterre Mts., Naho River Valley, nr. Moro , ex gravel banks of small fast stream, 1432 m, 5° 50' S, 146° 7' E, 7 xi 1964, M. E. Bacchus (MEB 91) (10 NHM) .

Differential Diagnosis. Similar to H. acumena in habitus, size, plaques, and some male sexual dimorphisms (tubercle on first abdominal ventrite, meso- and metatarsi with long hair-like setae ( Figs. 66 , 79 ); differing therefrom by slightly coarser dorsal punctation and shape of the male protibial apex. Reliable determinations of the two species will require examination of the aedeagi, which distinctively differ ( Figs. 68, 81 ). Ventral structures, and the very complicated chaetotaxy of the tibiae are illustrated with SEMs ( Figs. 304–307 ).

Description. Size: holotype (length/width, mm): body (length to elytral apices) 1.70/0.69; head 0.27/0.38; pronotum 0.38/0.46, PA 0.40, PB 0.38; elytra 1.04/0.69. Dorsum piceous; legs and maxillary palpi dark brown.

Frons punctures ca. 1xef, 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 densely micropunctulate, dull. Genae raised, shining, without posterior ridge. Pronotum cordiform, median 2/3 of anterior margin emarginate; punctures on disc ca. 1xpd those of frons, interstices shining, 2–4xpd, 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. 2–3xpd, as are interstices between punctures of a row, a few punctures random. 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. 3/4/11/1. P1 laminate; median carina sinuate in profile. P2 raised, l/w ca. 2/1, sides slightly converging toward blunt apex. Plaques very large, very narrowly separated, slightly more narrowly separated posteriorly than anteriorly, weakly raised. Metaventrite without midlongitudinal ridge. AIS width at straight posterior margin ca. 2x P2. All legs long and very slender. Profemur (male) with small, sharply pointed tubercle next to trochanter; protibia straight, distal 1/4 widened on anterior surface, apex with cluster of small spines, ventral margin with row of short spines on ridge, moderately long spine on medial surface at base of widened area. Mesotibia very slightly arcuate. Metatibia straight. Meso- and metatarsi with long hair-like setae along lower margin that lie flat on cuticle in dry specimens. First abdominal ventrite with large, sharply pointed tubercle in midline. Fifth abdominal ventrite not modified. Abdominal apex symmetrical; last tergite (male) deeply notched. Aedeagus as illustrated ( Fig. 68). Female tergite X, gonocoxite, and spermatheca as illustrated ( Fig. 395).

Etymology. Named in reference to the prominently thickened, strong and stiff left paramere, and the strong tubercle on the first ventrite of males.

Distribution. Currently known from a rather tight line of localities in eastern Area 1 (indicating a road, perhaps), and two localities in the Finisterre Mts. of Area 5; elevation range 1220–1700 m ( Fig. 461 ). This is one of ten species with distributions exclusively shared between Areas 1 and 5 ( Fig. 422 ).

Figures

FIGURE 66. Hydraena tetana, holotype, dorsal and lateral habitus, and venter.

FIGURE 79. Hydraena acumena, holotype, dorsal and lateral habitus, and venter.

FIGURES 304–309. Scanning electron micrographs of H. tetana (304–307) and H. tarsotricha (308–309).

FIGURES 459–462. Geographical distributions of Hydraena species.

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

FIGURES 421–422. 421. All known collecting localities for Papua New Guinea Hydraena. 422. Ten species, representing eight species groups, with distributions exclusively shared between Areas of Endemism 1 and 5.