Hydraena bacchusi, 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 : 95-96

Hydraena bacchusi , new species

( Figs. 162 , 164, 340–341 , 408 , 504 )

Type Material. Holotype (male): Eastern Highlands Province: 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) ( NHM) . Paratypes (152): 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 , gravel banks of deep fast river, 1524 m, 6° 32' S, 145° 37' E, 10 ii 1965, M. E. Bacchus (MEB 189a) (1 NHM) ; Okapa , on logs and vegetable debris in small river, 1524 m, 6° 32' S, 145° 37' E, 10 ii 1965, M. E. Bacchus (MEB 187a) (5 NHM) ; Okapa , under stones in small river, 1524 m, 6° 32' S, 145° 37' E, 10 ii 1965, M. E. Bacchus (MEB 186) (1 NHM) ; same locality, 10 ii 1965, M. E. Bacchus (MEB 187) (7 NHM) ; Umg. [=environs of] Igipinti, Korindaiop River , [GE est.] 600–1700 m, 6° 25' S, 145° 42' E, 18 vi 1979, W. G. Ullrich (22 MHNG) ; Umg. [=environs of] Okapa , [GE est.] 1500–1700 m, 6° 32' S, 145° 37' E, 18 vi 1979, W. G. Ullrich (2 MHNG) ; Waisa, nr. Okapa , in holes under stones in small fast river, 1524 m, 6° 38' S, 145° 32' E, 15 ii 1965, M. E. Bacchus (MEB 192a) (14 NHM) ; 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) (1 NHM) ; 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) (2 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) ; Madang Province: Finisterre Mts., Naho River Valley, Damanti , ex gravel bank of shallow stream, 1082 m, 5° 55' S, 145° 58' E, 12 x 1964, M. E. Bacchus (MEB 49) (2 NHM) ; Finisterre Mts., Naho River Valley, Moro , small stream running into River Naho , ex crevices in vertical rock, heavy water flow, 1372 m, 5° 50' S, 146° 7' E, 2 xi 1964, M. E. Bacchus (MEB 80) (4 NHM) ; Morobe Province: ridge between Aseki–Menyamya , 2200 m, 7° 12' S, 146° 4' E, 12 iv 1998, A. Riedel (1 NMW) ; Western Highlands Province: Kundum , 1400 m, 5° 16.096' S, 144° 27.869' E, 3 iii 2007, Kinibel ( PNG 142) (26 MCZ, NHM, NMW, PNG, ZSM) ; Sepik River Basin, Kil Stream , montane forest, 1800 m, 5° 40' S, 144° 42' E, 1 vii–30 viii 1988, D. Dudgeon (2 NMW) ; Simbai , 1800–2000 m, 5° 14.276' S, 144° 28.741' E, 1 iii 2007, Kinibel ( PNG 138) (11 MCZ, NHM, NMW, PNG, ZSM) ; Simbai, Kairong River , 1850 m, 5° 14.84' S, 144° 28.457' E, 2 iii 2007, Kinibel ( PNG 139) (36 MCZ, NHM, NMW, PNG, ZSM) .

Differential Diagnosis. Among members of the Cristatigena group that lack micropunctulate ground sculpture of the head and pronotum, most similar to H. tritutela ; differing therefrom by the smaller size (ca. 1.67 vs. 1.83 mm), the more truncate elytra, and the more discrete elytra serial punctures ( Figs. 162 , 163 ). In addition, the male hind tibiae are shaped differently in the two species. The male genitalia of the two species, while differing distinctively in several details, have a general shape that suggests relationship (figs. 164, 165). The maxillary palpi and metaventrite are illustrated with SEMs ( Figs. 340–341 ).

Description. Size: holotype (length/width, mm): body (length to elytral apices) 1.67/0.80; head 0.26/0.44; pronotum 0.42/0.58, PA 0.49, PB 0.46; elytra 1.00/0.80. Dorsum dark brown to piceous, head and pronotal disc slightly darker, palpi brown, except distal 1/2 of last palpomere slightly darker.

Dorsum of head and pronotum densely punctate, interstices shining; punctures of frons disc and pronotal disc 1–2xef, interstices ca. 1xpd or slightly larger; punctures of clypeus distinct, smaller than punctures of frons. Labrum apicomedially excised, lobes rounded, free margins upturned. Mentum very finely, sparsely punctate, shining; postmentum anterior 1/2 with punctation similar to mentum, posterior 1/2 densely micropunctulate. Genae raised, posterior ridge strong. Pronotum with anterior margin weakly emarginate over middle 1/2; all pronotal foveae moderately deep, PF3 and PF4 deeper than other foveae.

Elytra weakly shining, serial punctures very discrete, 1–2xpd of largest pronotal punctures, each puncture with three granules, one at anterior margin and one on each side. Intervals not raised, width 1–2xpd, as are interstices between punctures of a row. Apices in dorsal aspect conjointly rounded, in posterior aspect margins not forming angle with one another. Explanate margin well developed, about as wide as widest part of metatibia.

Ratios of P2 width and plaque shape (P2/w/l/s) ca. 3/1/8/6. P1 laminate; median carina sinuate in profile. P2 moderately narrow, l/w ca. 2/1, sides parallel, apex blunt. Plaques very narrow, weakly raised, subcarinate, located at lateral margins of median depression. Metaventrite tumid lateral to plaques. No midlongitudinal carina between mesoventral intercoxal process and plaques. Hydrofuge pubescence dense. AIS flat, width at straight posterior margin ca. 2x P2. Protibia (male), in ventral view, subapically on medial surface slightly widened and bearing few short stout setae, surface slightly but distinctly emarginate between widened part and; mesotibia slightly emarginate subapically on medial surface; metatibia markedly arcuate, medial surface flat or slightly concave, distal 1/3 distinctly widened and bearing short setal brush on upper surface. Abdominal apex symmetrical.

Aedeagus ( Fig. 164) main piece with small distal lobe, in ventral aspect apically produced in two small lobes; left paramere large, larger than distal lobe of main piece, markedly bilobed, each lobe with cluster of setae; right paramere very large, wide, apically rounded, in right lateral aspect arcuate toward ventral surface, setae in two clusters; distal piece with characteristic shape. Female tergite X, gonocoxite, and spermatheca as illustrated ( Fig. 408 ).

Etymology. Named in honor of Mick Bacchus, who expertly collected more than 3,700 specimens used in this study.

Distribution. Currently known from several localities in eastern Area 1 (1370–2200 m), and two localities in the Finisterre Mts., in Area 5 (1082 m) ( Fig. 504 ). This is one of ten species with distributions exclusively shared between Areas 1 and 5 ( Fig. 422 ).

Notes. In addition to the leg sexual dimorphism, the last maxillary palpomere is wider in males, and the pronotal foveae are slightly deeper in females.

Figures

FIGURE 162. Hydraena bacchusi, holotype, dorsal and lateral habitus, and venter.

FIGURE 163. Hydraena tritutela, holotype, dorsal and lateral habitus, and venter.

FIGURES 340–345. Scanning electron micrographs of H. bacchusi (340–341), H. variopaca (342) and H. cristatigena (343– 345).

FIGURES 408–411. Female tergite X, gonocoxite, and spermatheca of Hydraena species.

FIGURES 503–506. Geographical distributions of Hydraena species.

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.