Hydraena ypsilon 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 : 50-51

Hydraena ypsilon Zwick, 1977

(Figs. 73, 81, 82, 213, 232, 257)

Hydraena ypsilon Zwick, 1977: 166 .

Type Material. Holotype (male): Victoria, Fryer's Creek near mouth into Lake Eildon [labels: Australia, Vic, Fryers Creek n. Lake Eildon 3.x.1972 Zwick // Hydraena ypsilon Zwick Holo-Typus des. P. Zwick 1977 / / DIGITAL IMAGE captured 2004 P. D. Perkins]. Deposited in the MVMA.

Differential Diagnosis. Externally very similar to members of the ambiflagellata Group (Figs. 73, 147– 150); reliable determinations will require examination of the male genitalia (Fig. 81, 82).

Description. Size: holotype (length/width, mm): body (length to elytral apices) 1.45/0.61; head 0.20/ 0.32; pronotum 0.35/0.46, PA 0.36, PB 0.45; elytra 0.90/0.61. Dorsum dark brown, anterior and posterior margins of pronotum slightly lighter, legs and tips of maxillary palpi testaceous. Dorsum strongly shining, punctures each with very fine, indistinct recumbent seta.

Frons punctures ca. 1–2xef; interstices shining, 1xpd laterally, 2–4xpd medially. Clypeus microreticulate laterally, very 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 and deeper at anterior, similar to lateral area of frons; PF1 and PF4 absent; PF2 shallow, nearly absent; PF3 shallow, broad.

Elytral punctures slightly smaller and shallower largest pronotal punctures. Intervals not raised, shining, width about 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. 1/1.2/6/0.8/. P1 laminate; median carina posterior extreme slightly more elevated than remainder. P2 narrow, l/w ca. 2/1, sides nearly parallel, slightly widened toward apex blunt. Plaques arcuate, well delimited, slightly raised, narrowly confluent anteriorly, located in posterior 7/10 of metaventrite on sides of deep narrow depression. AIS flat, width at arcuate posterior margin 2–3x P2. Protibia (male) weakly widened on inner surface subapically. Metatibia (male) slender, gradually and very slightly increasing in width over length; distal 1/2 on inner surface with fringe of setae which at its widest is ca. width of tibia (visible in fluid; setae lie almost flat on cuticle in dry specimens). Last sternite slightly asymmetrical; last tergite with deep, slightly off-center concavity.

Aedeagus (Fig. 81, 82) main-piece with right side extended, hence aedeagus Y-shaped in ventral view; distal piece with long gonopore bearing flagellum and basal process that is triangular in ventral view; left paramere much larger than right, setae in row along widened margin; right paramere inserting on process of main-piece, well distal to insertion of left paramere. Female last tergite with apicomedian incision delimiting two lobes, setae on disc slender, tips tapering, setae along margin with tips blunt and angled ventrad, forming very discrete row on each side; gonocoxite and spermatheca as illustrated (Figs. 213, 232).

Distribution. Currently known from Victoria, Australian Capital Territory, and southern New South Wales (Fig. 257).

Material Examined (85): Australian Capital Territory, 7 km NW Tharwa, Paddy's River , 35° 31' S, 149° 4' E, 1 January 2001, W. D. Shepard (1 MCZ) ; New South Wales, Megalong Vy., Blue Mts. , elev. 304.8 m, 33° 43' S, 150° 15' E, 20 January 1932, P. J . Darlington (10 MCZ) ; Victoria, Dandenong Creek at Brady Road, Dandenong North , mud at edge of artificial dam in pasture, elev. 30 m, 37° 57' S, 145° 13' E, 28 September 1999, N. Porch (53) (1 ANIC) ; Healesville, Dandenong Ranges , 37° 39' S, 145° 32' E, 1–30 December 1968, C. Watts (6 SAMA) ; Holey Plains State Park, firedam on Crooke Track , fine sand and organics at the edge of a small firedam in dry sclerophyll forest, elev. 45 m, 38° 10' S, 146° 20' E, 16 April 2002, N. Porch (87) (54 ANIC) ; 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) (2 ANIC) ; Little River at Bacchus Marsh / Geelong Road , sandy gravel and muddy sand at edge of still pool of perennial creek in riparian forest remnants, elev. 105 m, 37° 50' S, 144° 23' E, 20 October 1999, N. Porch (36) (1 ANIC) ; Merriman Creek, 2.0 km NW Seaspray , gravel at base of gravel bank of small creek; pasture, elev. 5 m, 38° 21' S, 147° 9' E, 7 April 1999, N. Porch & N. Krause (50) (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 (5 PZC) ; same locality, 37° 44' S, 145° 29' E, 4 November 1972, P. Zwick (1 NMW, 3 PZC) .