Hydraena biimpressa, 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 : 42

Hydraena biimpressa new species

( Figs. 60 , 62, 62 )

Type Material. Holotype (male): Queensland, 19.5 km ESE Mareeba , MDPI intercept trap site No. 9a, 17° 1' S, 145° 35' E, 13 January–3 February 1987, R. I. Storey. Deposited in the QMBA.

Differential Diagnosis. Similar to H. hypipamee in body size, the large, deep pronotal foveae PF2, and dorsal punctation; differing therefrom in the brown and slightly less transverse pronotum, the smaller elytra, and the minute, nearly imperceptible plaques ( Figs. 60 , 100). The aedeagi of the two species distinctively differ ( Figs. 62 , 103).

Description. Size (length/width, mm) holotype: body (length to elytral apices) 1.39/0.60; head 0.25/ 0.34; pronotum 0.34, PA 0.35, PB 0.35; elytra 0.80/0.60. Dorsum brown, frons darker, marginal areas of pronotum slightly lighter; legs brown; labrum and maxillary palpi testaceous, tip of last palpomere not darker.

Frons punctures ca. 1xef; interstices shining, 1–3xpd. Clypeus microreticulate laterally, finely sparsely punctate medially. Mentum shining, very finely sparsely punctate; postmentum microreticulate. Genae raised, lacking posterior ridge. Pronotum cordiform, anterior margin emarginate; punctures on disc ca. 1– 1.5xpd than those of frons, interstices shining, 2–4xpd, punctures larger and denser anteriorly and posteriorly, interstices sometimes narrow walls forming reticulate pattern; PF1 united to form shallow transverse impression across anteromedian 1/3 of pronotal disc; PF2 large, deep, oval, oblique, separated by less than width of a fovea; PF3 deep, broad; PF4 moderately deep.

Elytra very convex, especially over posterior declivity; on basal 1/3 punctures large ca. 1xpd largest pronotal punctures, punctures becoming much smaller and much sparser over posterior declivity. Intervals not raised, shining, width over basal 1/3 ca. 1xpd, interstices between punctures of a row slightly larger. Apices in dorsal aspect conjointly rounded, in posterior aspect margins do not form angle with one another.

Ratios of P2 width and plaque shape (P2/w/l/s) ca. 4/0.1/2/4. P1 narrow, not laminate, median carina straight, or nearly so, in lateral view. P2 wide, short, l/w ca. 1/1, sides parallel, apex blunt. Plaques almost imperceptible, very thin, short, indistinct lines located on sides of deep median, triangular depression. AIS large, flat, width at straight posterior margin almost 2x P2. Legs slender, simple. Last sternite symmetrical; last tergite with deep apicomedian notch.

Aedeagus ( Fig. 62 ) small and simple; main-piece widened distally in ventral view, with process at distal extreme that continues from right to left; distal piece short, gonopore-bearing process with very short flagellum, behind which is large hairy lobe on dorsal surface; left and right parameres short, inserting at same level, about equal in length and each with sparse setae apically. Females not yet known.

Etymology. Named in reference to the two deep pronotal foveae.

Distribution. Currently known only from the type locality near Mareeba, northeastern Queensland (Fig. 262).

Figures

FIGURES 57–60. Hydraena, dorsal and lateral habitus of holotypes. —57. H. hynesi. —58. H. monteithi. —59. H. billi. —60. H. biimpressa.

FIGURES 61–64. Hydraena, aedeagi of holotypes. —61. H. billi. —62. H. biimpressa. —63. H. billi (after Zwick 1977). —64. H. monteithi.