Hydraena ferethula, 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 : 80-81

Hydraena ferethula new species

(Figs. 124, 130, 261)

Type Material. Holotype (male): Northern Territory, Cooper Creek , 19 km E by S of Mt. Borradaile, in sand at edge of stagnant pool, 12° 6' S, 133° 4' E, 3 November 1972, E. Britton. Deposited in the ANIC.

Differential Diagnosis. Among species of the parva subgroup , most similar in body proportions and dorsal punctation to H. parva and H. ambiosina (Figs. 122, 124, 133); differing therefrom by the larger size (ca. 1.36 vs. 1.25 mm), and the lack of plaques. The male genitalia of the three species distinctively differ (Figs. 126–128, 130, 132).

Description. Size (length/width, mm) holotype: body (length to elytral apices) 1.36/0.57; head 0.23/ 0.41; pronotum 0.34/0.45, PA 0.37, PB 0.42; elytra 0.80/0.57. Dorsum brown, except head and disc of pronotum piceous, legs brown, palpi testaceous, distal 1/2 of last palpomere darker.

Frons punctures ca. 1xef; interstices shining, 1–2xpd. Clypeus microreticulate laterally, finely sparsely punctate medially. Mentum and postmentum weakly shining, weakly microreticulate. Genae weakly raised, lacking posterior ridge. Pronotal punctures on disc ca. 1–2xpd those of frons, interstices shining, 0.5–2xpd, punctures denser anteriorly and posteriorly; PF1 and PF4 absent; PF2 very shallow, almost absent; PF3 shallow, broad.

Elytral punctures near base ca. 1xpd of largest pronotal punctures, becoming finer posteriorly. Intervals not raised, shining, width about 2xpd, as are interstices between punctures of a row. Each elytron with sublat- eral depression, bordered laterally by rounded ridge. Apices in dorsal aspect conjointly rounded, in posterior aspect margins form moderate angle with one another.

Plaques absent, metaventral depression moderately deep, wide. P1 laminate; median carina weakly angulate in profile. P2 l/w ca. 5/3, sides parallel, apex blunt. AIS flat, width at arcuate posterior margin 2x P2. Protibia very weakly arcuate, almost straight, other legs simple. Last sternite with small tooth that fits together with slightly asymmetrical last tergite.

Aedeagus (Fig. 130) main-piece moderately wide, with small, sharp process distally on right side; basal orifice very asymmetrical, twisted to right; distal piece large but comparatively simple, gonopore bearing flagellum moderately long, median or nearly so in ventral view; parameres inserting at same level; left paramere slender, setae in two groups, apical and subapical; right paramere thicker than left, bent ventrad apically, setae about four, clustered on ventral margin slightly past midlength. Females not yet known.

Etymology. "Almost the farthest North"; named in reference to the known distribution.

Distribution. Currently known only from the type locality in northern Northern Territory (Fig. 261).