Hydraena triloba, Published, 2007

PERKINS, PHILIP D., 2007, A revision of the Australian species of the water beetle genus Hydraena Kugelann (Coleoptera: Hydraenidae), Zootaxa 1489 (1), pp. 1-207 : 104-105

Hydraena triloba new species

(Figs. 172, 175, 256)

Type Material. Holotype (male): Queensland, Mulgrave River, Goldsborough Road Crossing , 17° 13' S, 145° 45' E, 20 May 1976, E. B. Britton. Deposited in the ANIC . Paratypes (33): New South Wales, Cabbage Tree Creek, Clyde Mtn. , in wet sand at stream edge, 35° 35' S, 150° 1' E, 28 November 1993, S. A. Slipinski & J. F. Lawrence (2 ANIC) ; Oberon , 27.5 km NW, in river debris, 33° 31' S, 149° 43' E, 17 November 1991, T. Gush (3 ANIC) ; Royal National Park , stream drift, FMHD #83-265 , 34° 3' S, 151° 3' E, 14 July 1983, L. E. Watrous (5 FMNH) ; Shaw Creek, Springwood / Richmond Rd. , elev. 8 m, 33° 38' S, 150° 38' E, 24 March 1965, M. E. Bacchus (MEB 214) (1 BMNH) ; Queensland, 30 km NE Brisbane, Mt. Nebo Road, Pond, ca. 200 m, Sclerophyll forest , elev. 540 m, 27° 24' S, 152° 48' E, 21 August 2004, M. A. Jäch (AU 1) (4 NMW) ; Flaggy Creek, 30 km N Kuranda, Black Mtn. Rd. , 16° 49' S, 145° 38' E, 29 November 1990, D. Larson (2 MCZ) ; Goolagan Creek., Palmerston H’way, 18 mi. SW Inisfail, 17° 37' S, 145° 43' E, 1 January–30 December 1987, J. Balfour-Browne (1 BMNH) ; Kauri Creek, Tinaroo L., NE Atherton, 17° 24' S, 145° 29' E, 24 October 1990, D. Larson (1 MCZ) ; Mulgrave River, Goldsborough Road Crossing , 17° 13' S, 145° 45' E, 20 May 1976, E. B. Britton (2 ANIC) ; Nigger Cr. trib., 23 km S Atherton, 17° 16' S, 145° 24' E, 18 October 1990, D. Larson (1 MCZ) ; Victoria, Cann River, at crossing of WB Line , littery sand and gravel at edge of small river; dry sclerophyll forest, elev. 215 m, 37° 20' S, 149° 12' E, 10 April 2000, N. Porch (30) (5 ANIC) ; Tambo River at Miller Access Road, south of Ensay , sandy mud of small backwater pool of river flowing through pasture, elev. 210 m, 37° 23' S, 147° 50' E, 16 December 2001, N. Porch (NP 82) (6 ANIC) .

Differential Diagnosis. Similar to H. zwicki in color, dorsal sculpture, and plaques; differing therefrom by the slightly larger size (ca. 1.40 vs. 1.31 mm), the more elongate elytra, and the more widely spaced elytra punctures (Figs. 174, 175). The aedeagi of the two species distinctly differ ( Figs. 10 , 172).

Description. Size (length/width, mm) holotype: body (length to elytral apices) 1.40/0.58; head 0.23/ 0.34; pronotum 0.35/0.45, PA 0.38, PB 0.43; elytra 0.85/0.58. Head dark brown to piceous; pronotum with dark brown macula surrounded anteriorly and posteriorly by testaceous, middle 1/3 of length, between macula and lateral margin, of intermediate color; elytra dark brown; legs and palpi testaceous, tip of palpi not darker.

Frons effacedly microreticulate, punctures less than 1xef; interstices weakly shining, 2–6xpd. Clypeus microreticulate laterally, finely sparsely punctate medially. Mentum shining, very finely sparsely punctate; postmentum microreticulate. Genae raised, lacking posterior ridge. Pronotal punctures on disc only slightly larger than those on frons, interstices shining, ca. 2–6xpd; punctures larger anteriorly and posteriorly, ca. 2xpd of discal punctures, interstices ca. 1xpd; PF1 and PF4 absent; PF2 very shallow, almost absent; PF3 shallow, broad.

Elytral punctures on disc slightly smaller than largest pronotal punctures, becoming finer posteriorly. Intervals not raised, shining, width about 2–3xpd, as are interstices between punctures of a row. Apices in dorsal aspect conjointly rounded, in posterior aspect margins form strong angle with one another.

Plaque/intercoxal process ratios (P2/w/l/s) ca. 2/2/7/3. P1 laminate; median carina angulate in profile. P2 l/w ca. 2/1, sides parallel, apex blunt. Plaques located in posterior 1/2 of metaventrite on sides of deep median triangular depression, slightly raised, tapering anteriorly, almost confluent at anterior extreme. AIS flat, width at arcuate posterior margin ca. 2x P2. Protibia (male) slightly arcuate, distal 1/2 slightly thickened; mesotibia slender; metatibia slender, very weakly emarginate on inner surface over distal 3/4. Last sternite with small off-center lobe; last tergite with deep, off-center notch, located opposite sternite lobe.

Aedeagus (Fig. 172) main-piece weakly angulate in ventral view, with three short processes on ventral surface; distal piece shorter than main-piece, with (in lateral view) two large, ovoid, rather flat processes, gonopore-bearing flagellum moderately long; parameres inserting at same level on main-piece; left paramere narrow, widest near base, then tapering to sharp tip, long setae in row along ventral margin; right paramere very narrow in basal 1/3, then widened, setae in two groups, some setae quite thick. Female last tergite subtriangular, with three incisions delimiting lobes, medial pair of lobes much larger than lateral pair, setae slender, tapering; subapical, sharp median process, at base of which issue long setae that join together at their tips, forming a "pencil" in dry specimens.

Etymology. Named in reference to the three lobes on the ventral face of the aedeagus.

Distribution. Currently known from Victoria, New South Wales, and Queensland, in three very disjunct populations (Fig. 256).

Figures

FIGURES 9–10. Aedeagi of holotypes. —9. H. reticulositis. —10. H. zwicki.