Hydraena darwini, 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 : 113

Hydraena darwini new species

(Figs. 187, 190, 261)

Type Material. Holotype (male): Northern Territory, Darwin , 12° 27' S, 130° 50' E, 13 May 1963, C. H. S. Watts. Deposited in the SAMA . Paratypes (26): Northern Territory, Same data as holotype (24 SAMA); Holmes Jungle , 11 km NE by E of Darwin, 12° 24' S, 130° 56' E, 24 March 1998, C. H. S. Watts (2 SAMA) .

Differential Diagnosis. Recognized by the combination of the coarsely, densely punctate pronotum, the confluent pronotal foveae PF2, the pronotum widest at midlength, and the nearly parallel-sided elytra (Fig. 187). The metatibiae of males are simple. Most similar to H. cubista (Fig. 186); differing therefrom by the pronotal shape, the confluent pronotal foveae PF2, and the aedeagal form (Figs. 189, 190).

Description. Size (length/width, mm) holotype: body (length to elytral apices) 1.39/0.56; head 0.22/ 0.32; pronotum 0.35/0.45, PA 0.36, PB 0.41; elytra 0.82/0.56. Head piceous, pronotum and elytra brown to dark brown, legs brown, palpi light brown, tip of palpi not darkened.

Head dull, microreticulate, frons punctures ca. 1.5xef; interstices 0.5–1xpd. Clypeus microreticulate. Mentum weakly shining, microreticulate. Genae weakly raised, lacking posterior ridge. Pronotum widest at midlength. Pronotum densely coarsely punctate, punctures on disc ca. 2–3xpd those of frons, interstices generally narrow walls forming reticulate pattern, slightly sparser on portion of disc; PF1 absent; PF2 small, shallow, united by very shallow impression. PF3 moderately deep, wide; PF4 absent.

Elytral nearly parallel-sided, punctures about equal size of largest pronotal punctures. Intervals not raised, shining, width ca. 1xpd, as are interstices between punctures of a row. Apices in dorsal aspect conjointly rounded to subtruncate, in posterior aspect margins forming angle with one another.

Ratios of P2 width and plaque shape (P2/w/l/s) ca. 2/1/3/2. P1 laminate; median carina angulate in profile. P2 moderately narrow, l/w ca. 5/2, sides parallel, apex blunt. Plaques narrow, not raised, located in posterior 7/10 of metaventrite on sides of deep median elongate subtriangular depression, plaques nearly parallel, wider posteriorly than anteriorly. No midlongitudinal carina between mesoventral intercoxal process and plaques. Cuticle asperite under hydrofuge pubescence. AIS flat, width at arcuate posterior margin ca. 2x P2. Profemur (male) with small, sharp tubercle on medial surface near basal 1/3; protibia very weakly arcuate, gradually increasing in width from base to apex; mesotibia simple; metatibia slender, straight, without setal brushes. Abdominal apex asymmetrical.

Aedeagus (Fig. 190) main-piece with large, strongly sclerotized process on ventral surface, near base; left paramere very large, with setae in two groups, apical group strong and long, group on ventral margin very short and weak; right paramere long, with setae in three groups, distal part widened and forming small lobe on ventral margin. Female last tergite with three incisions, delimiting four lobes, setae slender, tapering.

Etymology. Named in reference to the evolutionary biologist, and the locality of origin.

Distribution. Currently known from two narrowly separated localities near Darwin, northern Northern Territory (Fig. 261).