Hydraena forticollis, 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 : 113-114

Hydraena forticollis new species

(Figs. 188, 191, 260)

Type Material. Holotype (male): Western Australia, 4 km W of King Cascade, CALM Site 28/3 [Western Australian Department of Conservation and Land Management], 15° 38' S, 125° 15' E, at light, open forest, 12–16 June 1988, T. A. Weir. Deposited in the ANIC.

Differential Diagnosis. Recognized by the combination of the broad body form, the transverse pronotum which is microreticulate between the coarse punctures, the wide explanate margin of the elytra, and the widely separated plaques (Fig. 188). The metatibiae of males are simple. The aedeagus (Fig. 191) shows some simi- larity in basic form to the aedeagi of H. darwini and H. cubista (Figs. 189, 190); the pronotum is shaped differently in all three species, and only H. forticollis has microreticulate pronotal interstices.

Description. Size (length/width, mm) holotype: body (length to elytral apices) 1.32/0.65; head 0.21/ 0.36; pronotum 0.36/0.51, PA 0.40, PB 0.44; elytra 0.82/0.65. Head piceous, pronotum and elytra dark brown, legs and palpi brown, tip of palpi not darkened.

Head dull, microreticulate, frons punctures ca. 1.5xef; interstices 0.5–1xpd. Clypeus microreticulate. Mentum and postmentum weakly shining, microreticulate. Genae weakly raised, lacking posterior ridge. Pronotum widest at midlength. Pronotum microreticulate, densely, moderately coarsely punctate, punctures on disc ca. 2xpd those of frons, interstices generally 1xpd or slightly less; punctures denser anteriorly and posteriorly, sometimes narrow walls forming reticulate pattern; PF1 absent; PF2 small, moderately deep, separated by about width of fovea. PF3 and PF4 shallow, wide.

Elytral punctures on disc about equal size of largest pronotal punctures. Intervals not raised, shining, width ca. 1xpd, as are interstices between punctures of a row. Explanate margin moderately wide, continuing posteriorly to near apices; lateral margin arcuate. 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. 2/1/2/4. P1 laminate; median carina angulate in profile. P2 moderately narrow, l/w ca. 2/1, sides parallel, apex blunt. Plaques short and narrow, located on posterior sides of median depression, converging slightly anteriorly, not raised. 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. Last tergite cap-like, with asymmetrical concavity.

Aedeagus (Fig. 191) main-piece with large, strongly sclerotized process on ventral surface, near base; left paramere very large, with setae in two groups, apical group longer and clustered, group along ventral margin very short and sparse, in a row, three small tubercles near base; right paramere long, with setae in three groups, distal part widened and forming small lobe on ventral margin. Females not yet known.

Etymology. Named in reference to the comparatively large prothorax.

Distribution. Currently known only from the type locality near King Cascade, in northeastern Western Australia (Fig. 260).