Hydraena ambiflagellata Zwick, 1977

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 : 89-90

Hydraena ambiflagellata Zwick, 1977

(Figs. 148, 155, 156, 240)

Hydraena ambiflagellata Zwick, 1977: 169 .

Type Material. Holotype (male): Victoria, stagnant branch of Woori Yallock Creek on road to Warburton [labels: Australia, Vic., Wng Melbourne, Woori Yallock Cr. 4.xi.1972 Zwick // Hydraena ambiflagellata Zwick Holo-Typus des. P. Zwick, 1977 // DIGITAL IMAGE captured 2004 P. D. Perkins]. Deposited in the MVMA.

Differential Diagnosis. Externally very similar to other members of the ambiflagellata Group (Figs. 147–150); reliable determinations will require examination of the male genitalia (Figs. 155, 156). Males, and some females, have a small tubercle on the lateral margin of each plaque; these are not present in the other members of the ambiflagellata group.

Description. Size: holotype (length/width, mm): body (length to elytral apices) 1.38/0.58; head 0.17/ 0.32; pronotum 0.34/0.46, PA 0.37, PB 0.44; elytra 0.88/0.58. Dorsum dark brown, anterior and posterior margins of pronotum light brown to testaceous, legs testaceous, maxillary palpi brown except testaceous tip. Dorsal punctures each with a fine recumbent seta.

Frons punctures ca. 1–2xef; interstices shining, 0.5–3xpd. Clypeus microreticulate laterally, finely sparsely punctate medially. Mentum shining, very finely sparsely punctate; postmentum microreticulate. Genae raised, lacking posterior ridge.

Pronotal punctures on disc ca. 1xpd those of frons, interstices shining, 2–6xpd, punctures denser at anterior; PF1 and PF4 absent; PF2 very shallow, nearly absent; PF3 shallow, broad.

Elytral punctures about equal size of largest pronotal punctures. Intervals not raised, shining, width ca. 2– 3xpd, as are interstices between punctures of a row. Apices in dorsal aspect gradually rounded, in posterior aspect margins form shallow angle with one another.

Ratios of P2 width and plaque shape (P2/w/l/s) ca. 3/3/8/3. P1 laminate; median carina posterior extreme slightly more elevated than remainder. P2 narrow, l/w ca. 2/1, sides nearly parallel, apex widened toward blunt apex. Plaques very weakly arcuate, well delimited, slightly raised, convergent but only slightly tapering anteriorly; lateral margin with minute subtubercle near midlength; located in posterior 7/10 of metaventrite on sides of deep median triangular depression. No midlongitudinal carina between mesoventral intercoxal process and plaques. Cuticle asperite under hydrofuge pubescence. AIS flat, width at arcuate posterior margin 2–3x P2. Protibia (male) weakly widened on inner surface subapically; metatibia slender, gradually and very slightly increasing in width over length; distal 1/2 on inner surface with fringe of setae that at its widest is ca. width of tibia (visible in fluid; setae lie almost flat on cuticle in dry specimens). Last sternite very slightly asymmetrical; last tergite with very small, slightly off-center concavity.

Aedeagus (Figs. 155, 156) main-piece wide in both views, process on right side terminating in flagellum; distal piece much larger than process of main-piece, irregularly shaped, thickened on dorsal surface, with long gonopore bearing flagellum; left paramere very broad, shorter than right, setae long, in row across arcuate distal margin; right paramere inserting slightly more distally than left paramere, sinuate, widened in distal 1/2, setae long, in two groups, one group on each side of main-piece process. Female last tergite with three incisions, delimiting four lobes, setae slender, tapering.

Distribution. In Australia currently known from South Australia, Victoria, and Tasmania (Fig. 240). Also known from New Zealand; most likely introduced by human agency ( Delgado and Palma 1997).

Material Examined (77): Australian Capital Territory, Tidbinbilla Nature Reserve , trickle at campground, 35° 28' S, 148° 54' E, 6 October 2002, P. Zwick (9 PZC) ; South Australia, 10 km N Forreston , 34° 44' S, 138° 57' E, 13 October 2002, C. H. S. Watts (17 SAMA) ; 13 km W Meadows , 35° 11' S, 138° 37' E, 26 September 1996, C. Watts (1 SAMA) ; Adelaide , Belair N. P., Paroomba Creek, elev. 300 m, 34° 59' S, 138° 38' E, 3 December 1999, L. Hendrich (3 NMW) ; Mt. Gambier , 37° 50' S, 140° 45' E, 1–30 December 1961, C. Watts (1 SAMA) ; Mt. Lofty Range , 34° 58' S, 138° 42' E, 1–30 November 1931, P. J. Darlington (8 MCZ) ; S Mt. Lofty Ranges, 30 km SE Adelaide, Scott Creek Conservation Park , 35° 5' S, 138° 41' E, 18 December 1999, Hands & Hendrich (1 NMW) ; Tasmania, Fossey River on road to Rosebery , 41° 27' S, 145° 38' E, 2 December 1972, P. Zwick (1 PZC) ; Hobart , 42° 52' S, 147° 19' E, 17 April 1917, C. E. Cole (1 SAMA) ; same locality, 42° 52' S, 147° 19' E, 1–30 August 1961, C. Watts (2 SAMA) ; Mount, creek Barrow , inundation debris, 41° 22' S, 147° 21' E, 8 December 1982, Endrödy-Younga (AU 101) (3 TMSA) ; St. Patric River, Targa , inundation debris, 41° 18' S, 147° 21' E, 8 December 1982, Endrödy-Younga (AU 104) (5 TMSA) ; Tasman Hwy. , 6 km S Llandaff, elev. 50 m, 41° 56' S, 148° 12' E, 3 February 1998, L. Hendrich (1 NMW) ; Victoria, Bright [no date], 36° 46' S, 146° 59' E ,, H. W. Darvey (3 MVMA) ; Kangaroo Creek on Springhill Rd. , 5.8 km E Glenlyon, amongst weeds in shallow water at edge of creek (perennial) pools, dry sclerophyll forest, elev. 510 m, 37° 18' S, 144° 18' E, 31 January 1999, N. Porch (NP 24a) (1 ANIC) ; Lerderderg River , 4.8 km WNW Blackwood; 332, 37° 30' S, 144° 19' E, 30 April 1983, A. J. Boulton (1 ANIC) ; Stagnant branch of Woori Yallock Creek on road from Melbourne to Warburton , 37° 44' S, 145° 29' E, 11 October 1972, P. Zwick (1 NMW, 8 PZC); same locality, 37° 44' S, 145° 29' E, 4 November 1972, P. Zwick (6 PZC) ; Warburton , 37° 42' S, 145° 44' E, 13 March 1921, C. Oke (4 MVMA) .