Hydraena decipiens 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 : 90-91

Hydraena decipiens Zwick, 1977

(Figs. 149, 150, 153, 154, 260)

Hydraena decipiens Zwick, 1977: 167 .

Type Material. Holotype (male): Queensland, south of Charleville [ca. 26° 24' S, 146° 20' E] [labels: S. of Charleville, Q. 9.v.73, M.S. Upton // [pink label] // Holotype // Aedeagus drawn by P. D. Perkins // DIGITAL IMAGE captured 2004 P. D. Perkins // Hydraena decipiens Zwick Holo-Typus des. P. Zwick 1977]. Deposited in the ANIC.

Differential Diagnosis. Externally very similar to other members of the ambiflagellata Group (Figs. 147–150); reliable determinations will require examination of the male genitalia (Fig. 153, 154).

Description. Size: holotype (length/width, mm): body (length to elytral apices) 1.50/0.58; head 0.21/ 0.33; pronotum 0.37/0.47, PA 0.37, PB 0.46; elytra 0.90/0.58. Head dark brown, pronotum with brown macula surrounded by testaceous; elytra brown; legs light brown; maxillary palpi testaceous, tip of last palpomere slightly darker.

Frons punctures laterally ca. 1xef, medially ca. 0.5xpd; 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 2xpd largest frons punctures, interstices shining, 1–3xpd, punctures slightly denser and deeper at anterior and posterior; PF1 and PF4 absent; PF2 very shallow, nearly absent; PF3 moderately deep, broad.

Elytral punctures basally slightly smaller than largest pronotal punctures, becoming slightly finer over posterior declivity; a few punctures on disc not distinctly serial. Intervals not raised, shining, width 1–2xpd, interstices between punctures of a row slightly greater. 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. 3/3/8/2. P1 laminate; median carina angulate in profile. P2, l/w ca. 2/1, sides parallel, apex blunt. Plaques large, raised, very weakly arcuate, narrowly separated, converging and almost becoming confluent anteriorly. Low midlongitudinal ridge between P2 and plaques. AIS flat, width at arcuate posterior margin slightly less than 2x P2. Protibia (male) weakly arcuate, widened on inner surface subapically; metatibia slender, very weakly arcuate, distal 1/2 on medial margin with dense fringe of short setae that lie flat on cuticle. Last sternite symmetrical or nearly so; last tergite with small apicomedian emargination.

Aedeagus (Figs. 153, 154) main-piece extending as process on right side, about 1/3 as wide as distal piece, apex blunt; distal piece irregularly shaped, with several processes visible in ventral view, gonopore flagellum short; left paramere wide, almost trilobed on margin, two small distal lobes each with two long setae, ventral margin with row of setae; right paramere longer than left paramere, inserting at same level as left paramere, markedly angulate, ventral margin curling around main-piece and bearing setae in three groups. Female last tergite with three incisions, delimiting four lobes, setae slender, tapering.

Distribution. Currently known from two widely separated localities, inland in southern Queensland, and near coastal Victoria (Fig. 260).

Remarks. Male genitalia from the two known, widely separated localities differ in some minor details (Figs. 153, 154).

Material Examined (3): Victoria, Bacchus Marsh , 12 km W by N of, shallow, grassy, roadside ditch, and from litter and mud at edge of ditch, elev. 455 m, 37° 38' S, 144° 17' E, 17 September 2000, N. Porch (4) (3 ANIC) .