Hydraena kakadu, 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 : 82-83

Hydraena kakadu new species

(Figs. 77, 134, 262)

Type Material. Holotype (male): Northern Territory, Kakadu National Park, Gubara , elev. 50 m, 12° 16' S, 132° 40' E, 25 October 1996, L. Hendrich (1). Deposited in the SAMA . Paratype: Kakadu National Park , Gungurul Lookout, creek, elev. 50 m, 13° 59' S, 132° 19' E, 1 November 1996, L. Hendrich (1 NMW) .

Differential Diagnosis. Differentiated from other members of the parva Subgroup by the very coarse pronotal punctation, which is much coarser than the elytral punctation (Fig. 134); also differing from the other species, except H. ferethula , by the absence of plaques. The male genitalia of these two species distinctively differ (Figs. 77, 130).

Description. Size: holotype (length/width, mm): body (length to elytral apices) 1.29/0.53; head 0.21/ 0.30; pronotum 0.31/0.40, PA 0.34, PB 0.36; elytra 0.76/0.53. Head piceous; pronotum with piceous fascia bordered by testaceous, narrowly along base, more widely anteriorly; elytra dark brown; legs dark brown on basal 1/2 of femur, otherwise light brown; palpi testaceous to light brown.

Frons punctures slightly smaller than 1xef; interstices shining, 0.5–4xpd. Clypeus microreticulate laterally, finely sparsely punctate medially. Mentum and postmentum shining, very finely sparsely punctate. Genae raised, lacking posterior ridge. Pronotal punctures on disc ca. 3–5xpd and much deeper than those of frons, interstices shining, 1–3xpd on disc, punctures denser anteriorly; PF1 and PF4 absent; PF2 absent or nearly imperceptible; PF3 moderately shallow.

Elytral punctures very faint, much smaller than pronotal punctures. Intervals not raised, shining, width about 3xpd, as are interstices between punctures of a row. Each elytron with very weak sublateral depressed area just before midlength, bordered laterally by rounded ridge that continues from near base to about distal 3/ 4; area between ridge and elytral margin groove-like. Apices in dorsal aspect conjointly rounded, in posterior aspect margins form moderately strong angle with one another.

Plaques absent, median metaventral depression deep, subtriangular. P1 laminate; median carina angulate in profile. P2 moderately wide, l/w ca. 5/4, sides parallel, apex blunt. AIS flat, width at arcuate posterior margin slightly wider than P2. Protibia simple. Metatibia very slender, slightly widened over middle 1/3; inner margin over distal 1/2 with row of sparse, indistinct setae, recumbent in dry specimens. Last sternite and tergite asymmetrical, sternite with moderately deep off-center emargination into which fits irregular margin of tergite.

Aedeagus (Fig. 77) main-piece only moderately wide, lobe on left side distally, small median process distally, narrow, strong, sharp process distally on right side; basal orifice large, very asymmetrical; distal piece with very large, gonopore bearing process and, visible in lateral view, two U-shaped indentations, one distal to the other; parameres inserting at same level; left paramere slender, slightly longer than right, setae in two groups, apical and about five widely spaced along ventral margin; right paramere very strong, knife-shaped, with about five setae clustered on ventral margin near midlength. Females not yet known.

Etymology. Named in reference to the geographical distribution.

Distribution. Currently known from Kakadu National Park, northern Northern Territory (Fig. 262).