Hydraena brittoni 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 : 26-27

Hydraena brittoni Zwick, 1977

( Figs. 31 , 35, 36 , 239)

Hydraena brittoni Zwick, 1977: 177 .

Type Material. Holotype (male): Western Australia, Millstream [ca. 21° 35' S, 117° 4' E] [labels: (21.35S 117.04E) Millstream, WA., 2.xi.70 from gravel at edge of pool at pipe crossing. E. Britton // [pink label] Holotype // Aedeagus drawn by P. D. Perkins // DIGITAL IMAGE captured 2004 P. D. Perkins // Hydraena brittoni Zwick Holo-Typus des. P. Zwick 1977]. Deposited in the ANIC.

Differential Diagnosis. Very similar in habitus to H. simplicicollis ( Figs. 29–31 ); differing therefrom by the slightly narrower mesoventral process (compared to the plaque width), the slightly less widely separated plaques, and the slightly less coarse dorsal punctation. Reliable determinations will be based on examination of the aedeagi ( Figs. 33–36 ).

Description. Size: holotype (length/width, mm): body (length to elytral apices) 1.59/0.68; head 0.24/ 0.38; pronotum 0.43/0.51, PA 0.42, PB 0.46; elytra 0.99/0.68. Head piceous, pronotum piceous on disc, dark brown anteriorly and posteriorly, elytra dark brown, legs and maxillary palpi brown, tip of last palpomere not darker.

Frons punctures ca. 1xef; interstices shining, 0.5–2xpd. Clypeus microreticulate laterally, shining and finely sparsely punctate medially. Mentum shining, very finely sparsely punctate; postmentum microreticulate. Genae raised, lacking posterior ridge. Pronotal punctures on disc ca. 2xpd those of frons, interstices shining, 1–3xpd, punctures denser anteriorly and posteriorly, separated by narrow walls to 1xpd; PF1 and PF4 absent; PF2 very small, nearly absent; PF3 moderately deep, broad.

Elytral punctures about equal size of largest pronotal punctures. Intervals not raised, shining, width about 2xpd, 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. 3/1/8/4. P1 laminate; median carina slightly angulate in profile. P2 moderately wide, l/w ca. 3/4, sides parallel, apex blunt. Plaques located in posterior 7/10 of metaventrite on sides of deep median triangular depression, plaques narrow, straight, converging, anterior separation ca. 1/2 posterior separation. No midlongitudinal carina between mesoventral intercoxal process and plaques. AIS flat, width at arcuate posterior margin slightly less than 2x P2. All tibiae slender, simple. Last sternite symmetrical or nearly so; last tergite with apicomedian notch.

Aedeagus ( Figs. 35, 36 ) main-piece with pointed process on right side, shorter than right paramere, which is partially behind it; distal piece with several diagnostic processes; left paramere moderately wide in distal 1/ 2, setae at apex, about seven, very stout, setae along ventral margin, about five, widely spaced, long, and thin; right paramere sharpely pointed at apex, setae in row on ventral margin. Female last tergite with apicomedian incision delimiting two lobes, setae slender, tapering.

Distribution. Currently known from western Western Australia (Fig. 239).

Material Examined (89): Western Australia, 0.5 km WNW of Millstream , 21° 35' S, 117° 4' E, 7 April 1970, M. S. Upton (1 ANIC) ; 1 km N Red Hill Station , 21° 58' S, 116° 4' E, 22 May 2001, C. H. S. Watts (1 SAMA) ; 10 km NW Eerala Station , 21° 19' S, 117° 2' E, 23 May 2001, C. H. S. Watts (6 SAMA) ; Cane River, Hwy 1 crossing, 21° 58' S, 115° 35' E, 22 May 2001, C. H. S. Watts (2 SAMA) ; Millstream, Crossing pool, 21° 35' S, 117° 4' E, 24 May 2001, C. H. S. Watts (15 SAMA) ; Millstream, Crystal Pool , at light, 21° 35' S, 117° 4' E, 5 November 1970, E. B. Britton (1 ANIC) ; Millstream , gravel at water’s edge in pipe crossing pool, 21° 35' S, 117° 4' E, 2 November 1970, E. Britton (20 ANIC) ; Millstream , shallow stream, from gravel at edge of pool at pipe crossing, 21° 35' S, 117° 4' E, 2 November 1970, E. Britton (36 ANIC, 1 NMW) ; Millstream, shallow stream, gravel margins of Crossing Pool , 21° 35' S, 117° 4' E, 1 November 1970, E. Britton (2 ANIC) ; Millstream, waterside gravel in pipe Crossing Pool , 21° 35' S, 117° 4' E, 5 November 1970, E. Britton (3 ANIC) ; Woodstock Station , at UV florescent light at night 6:00 to 7:30 PM, 21° 37' S, 119° 1' E, 24 September 1988, B. P. Hanich (site WS 9) (1 WAMP) .

Figures

FIGURES 29–32. Hydraena, dorsal and lateral habitus of types. —29. H. simplicicollis, lectotype male. —30. H. simplicicollis, paralectotype female. —31. H. brittoni, holotype. —32. H. converga, holotype.

FIGURES 33–36. Hydraena, aedeagi of types. —33. H. simplicicollis, lectotype. —34. H. simplicicollis, lectotype (after Zwick 1977). —35. H. brittoni, holotype. —36. H. brittoni, holotype (after Zwick 1977).