Hydraena ambiosina, Published, 2007

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 : 81-82

Hydraena ambiosina new species

(Figs. 132, 133, 240)

Type Material. Holotype (male): Queensland, 7 km NE of Tolga , MDPI intercept trap 28, flight intercept trap, 17° 13' S, 145° 28' E, 20 February–9 March 1987, Storey & De Faveri. Deposited in the QMBA . Paratypes (45): Northern Territory, Kakadu N. P., Gungurul Lookout , creek, elev. 50 m, 13° 59' S, 132° 19' E, 1 November 1996, L. Hendrich (38 NMW) ; Queensland, 16 km SSE of Musselbrook Mining Camp , at light, 18° 44' S, 138° 12' E, 18 May 1995, T . Weir (1 ANIC); 18 km N Mareeba, intermittent stream, 16° 58' S, 145° 25' E, 20 September 1990, D. Larson (3 MCZ); 6 km W Dimbulah, 17° 8' S, 145° 6' E, 10 November 1990, D. Larson (1 MCZ); Murrays Spring , 8 km W by N of Musselbrook Mining Camp , large pool in rocky creek bed, sandy bottom water lillies, Pandanus , algal growth, 18° 35' S, 138° 3' E, 9–20 May 1995, T . Weir (2 ANIC) .

Differential Diagnosis. Among species of the parva subgroup , most similar in size, body proportions, dorsal punctation, and plaque configuration to H. parva ; differing therefrom by the less distinctively depressed sublateral area of the elytra, and the weaker sublateral ridge (Figs. 122, 133). Examination of the quite distinct male genitalia will be necessary for reliable determinations (Fig. 132).

Description. Size (length/width, mm) holotype: body (length to elytral apices) 1.25/0.52; head 0.22/ 0.26; pronotum 0.30/0.40, PA 0.33, PB 0.36; elytra 0.74/0.52. Head dark brown to piceous; pronotum anteriorly and posteriorly light brown to testaceous, large dark brown to piceous fascia across disc; elytra dark brown; legs and palpi light brown to testaceous.

Frons punctures ca. 1xef; interstices shining, 1–2xpd. Clypeus microreticulate laterally, finely sparsely punctate medially. Mentum and postmentum weakly shining, very finely sparsely punctate. Genae weakly raised, lacking posterior ridge. Pronotal punctures on disc ca. 1–2xpd those of frons, interstices shining, 1– 3xpd, punctures sparcer on disc; PF1 and PF4 absent; PF2 very shallow, almost absent; PF3 shallow, broad.

Elytral punctures ca. 1xpd of smallest pronotal punctures. Intervals not raised, shining, width about 2xpd, as are interstices between punctures of a row. Each elytron with sublateral depression, bordered laterally by rounded ridge. 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. 2/1/5/3. P1 laminate; median carina weakly angulate in profile. P2 l/w ca. 2/1, sides parallel or weakly diverging, apex blunt. Plaques located in posterior 7/10 of metaventrite on sides of moderately deep median subtriangular depression, plaques straight, tapering anteriorly. AIS flat, width at arcuate posterior margin ca. 2x P2. Legs simple. Last sternite with small marginal lobe, slightly off-center; last tergite with correspondingly small, off-center emargination.

Aedeagus (Fig. 132) main-piece wide, with small median process, and with sharp process distally on right side that, in ventral view, conceals apical part of right paramere; basal orifice very asymmetrical; distal piece with several more-or-less rounded lobes, gonopore bearing flagellum rather long, diagonally angled from right to left in ventral view; parameres inserting at same level, right paramere inserting on ventral surface; left paramere very slender, setae in two groups, apical and subapical; right paramere bisinuate in lateral view, with about four setae clustered on ventral margin near midlength. Female last tergite with three incisions, delimiting four lobes, setae slender, tapering.

Etymology. Named in reference to the distribution around the Gulf of Carpentaria.

Distribution. Currently known from three very disjunct populations in Queensland and Northern Territory (Fig. 240).