Hydraena extorris 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 : 94-95

Hydraena extorris Zwick, 1977

(Figs. 159, 164, 165, 260)

Hydraena extorris Zwick, 1977: 182 .

Type Material. Holotype (male): New South Wales [either in the vicinity of Sydney or the Blue Mountains] [labels: " Queensland, area of Sydney or Blue Mts. // Holotype // Aedeagus drawn by P. D. Perkins // DIGI- TAL IMAGE captured 2004 P. D. Perkins // Hydraena extorris Zwick Holo-Typus des. P. Zwick 1977 "].

Differential Diagnosis. Externally very similar to H. hamifera (Figs. 159, 160); differing therefrom by the more densely punctate pronotal disc, the narrower elytral explanate margin, the more widely separated plaques, and, in males, the simple metatibia. The aedeagi of the two species differ distinctively (Figs. 164, 165, 167).

Description. Size: holotype (length/width, mm): body (length to elytral apices) 1.70/0.71; head 0.26/ 0.41; pronotum 0.42/0.58, PA 0.47, PB 0.51; elytra 1.04/0.71. Head dark brown to piceous; pronotum and elytra brown; legs light brown; palpi testaceous, tip of last palpomere not darkened (the holotype is teneral and hence more lightly colored).

Frons punctures ca. 1xef; interstices shining, 1–2xpd. Clypeus microreticulate. Mentum shining, very finely sparsely punctate; postmentum microreticulate. Genae raised, lacking posterior ridge. Pronotal punctures on disc 2–3xpd and deeper than those of frons, interstices shining, varying from narrow walls forming reticulate pattern, to 1xpd; PF1 and PF4 absent; PF2 small, shallow; PF3 shallow, broad.

Elytral serial punctures very regular, about equal size of largest pronotal punctures; intervals not raised, shining, width less than puncture diameter, as are interstices between punctures of a row; apices in dorsal aspect conjointly rounded, in posterior aspect margins form shallow angle with one another.

Ratios of P2 width and plaque shape (P2/w/l/s) ca. 3/2/9/5. P1 laminate; median carina angulate in profile. P2 l/w ca. 5/3, sides parallel, apex blunt. Plaques located in posterior 3/5 of metaventrite at margin of median subtriangular depression, plaques straight, convergent anteriorly, each plaque gradually tapering anteriorly. AIS flat, width at arcuate posterior margin 2x P2. Protibia weakly arcuate, slightly thickened in distal 0.5; meso- and metatibia simple. Abdominal apex asymmetrical.

Aedeagus (Fig. 164, 165) main-piece with long, slender, arcuate, strongly sclerotized process on right side; base very asymmetrical; distal part of aedeagus with enlargement on ventral surface, best seen in lateral view; two terminal processes and one terminal lobe, gonopore bearing process on left side; left paramere angularly enlarged on ventral surface, setae in two groups; right paramere simple, longer than left paramere, setae in two groups. Female last tergite with three incisions, delimiting four lobes, setae slender, tapering.

Distribution. Currently known from southeastern Queensland and northeastern New South Wales (Fig. 260).

Material Examined (12): New South Wales, Armidale , 30° 30' S, 151° 39' E, 21 March 1963, C. Watts (1 SAMA) ; 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) (1 NMW) ; 90 km SW Brisbane, 40 km NE Warwick , 28° 3' S, 152° 22' E, 26 August 2004, M. A. Jäch (AU 17) (2 NMW) ; Girraween N. P., Bald Rock Creek at "Under-ground Creek", ex. sand/gravel streambank, 28° 51' S, 151° 57' E, 22 January 1998, P. D. Perkins (7 MCZ) ; Running Creek Road, SE Rathdowney, ca. 25 km SSE Beaudesert, small road side ditch (remnants of small swampy meadow), 28° 15' S, 152° 53' E, 25 August 2004, M. A. Jäch (AU 12) (1 NMW) .