Hydraena williamsensis Deane, 1931

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 : 23-24

Hydraena williamsensis Deane, 1931

( Figs. 22 , 27, 28 , 254)

Hydraena williamsensis Deane, 1931: 175 .

Hydraena williamsensis Deane ; Zwick, 1977: 163.

Type Material. Holotype (male): New South Wales, Upper Williams River [labels: Upper. Williams. R Oct. 1926. N.S.W. F. E. Wilson // 2271 Type // Hydraena williamsensis, Deane. Det. C. Deane // F. E. Wilson Collection // DIGITAL IMAGE captured 2004 P. D. Perkins]. Deposited in the MVMA.

Differential Diagnosis. A very broad species, similar in this respect to H. latisoror ( Figs. 21, 22 ); differing therefrom by the less densely, less coarsely punctate dorsum, the narrower mesoventral intercoxal process, the non-hydrofuge pubescent metaventral disc, and the obsolete plaques. The aedeagi of the two species differ distinctively ( Figs. 26–28 ).

Description. Size: holotype (length/width, mm): body (length to elytral apices) 1.52/0.64; head 0.23/ 0.38; pronotum 0.40/0.58, PA 0.44, PB 0.46; elytra 0.89/0.64. Dorsum dark brown, lateral areas of pronotum slightly lighter, legs brown, maxillary palpi brown to testaceous.

Frons punctures ca. 1.5xef; interstices shining, 0.5–3xpd. Clypeus microreticulate laterally, finely sparsely punctate medially. Mentum shining, very finely sparsely punctate; postmentum microreticulate. Genae raised, lacking posterior ridge. Pronotal punctures on disc ca. 2xpd and deeper those of frons, interstices shining, 1–3xpd, punctures denser at anterior; PF1 absent; PF2 distinct, oblique; PF3 very shallow. Area between PF3 and PF4 weakly convex. Anterior margin of pronotum broadly emarginate.

Elytral punctures about equal size of largest pronotal punctures. Intervals not raised, shining, width about 1xpd, as are interstices between punctures of a row. Apices in dorsal aspect conjointly moderately sharply rounded, in posterior aspect margins do not form angle with one another.

Ratios of P2 width and plaque shape (P2/w/l/s) ca. 1/5/6/5. P1 laminate; median carina posterior extreme slightly more elevated than remainder. P2 very narrow, l/w ca. 5/1, sides parallel, apex blunt. Plaques indistinct, not well delimited laterally, punctate, located on each side of deep oval depression. No midlongitudinal carina between mesoventral intercoxal process and plaques. Carina behind mesocoxae strong. Disc of metaventrite lacking hydrofuge pubescence. AIS flat, width at straight posterior margin 5x P2. All femora thickened. Protibia widest at midlength, prominent spine on inner surface at distal 3/5. Mesotibia widest near midlength. Metatibia weakly emarginate on inner surface over distal 3/4. All tarsi short, ca. 1/3 width of pronotum. Last sternite symmetrical or nearly so; last tergite cap-like.

Aedeagus ( Figs. 27, 28 ) main-piece with distal extended part arcuate, continuing slightly beyond distal piece; distal piece with two lobes, the left slightly larger than the right, and with two processes on the left margin; left paramere slender, straight, much longer than right paramere, with cluster of about five setae on inner margin at apex; right paramere slightly arcuate, with setae in two groups at apex. Female last tergite with rather deep apicomedian incision delimiting two lobes, setae slender, tapering.

Distribution. A rarely collected species, currently known from New South Wales (Fig. 254).

Remarks. This species has been collected from streamside flood debris, wet leaf litter, and rotten wood litter, indicating that it is probably semi-humicolous in habits. The morphology concurs with this prediction, having characters similar to other Hydraena collected in litter: 1) a broad body form, 2) strong dorsal punctation, 3) short stout legs with enlarged femora and short tarsi, and 4) obsolete metaventral plaques.

Material Examined (17): New South Wales, 48 km N Singleton, Tuglo Wildlf. Ref. , rainforest litter along “Turkey Crk.”, FMHD #83-283 , 33° 56' S, 149° 59' E, 23 July 1983, L. E. Watrous (1 FMNH); Dorrigo N. P., Never Never Picnic area , 12 km E Dorrigo, Cedar Falls Trail, Berlesate ANIC 1601 , cut warm temp. closed forest, rotten wood litter, elev. 730 m, 30° 22' S, 152° 48' E, 22 May 1993, D. S. Chandler (10 ANIC); Dorrigo N. P., Sassafras Creek, upstream from Casuarina Falls , ex. bare rocks in splash zone, elev. 650 m, 30° 22' S, 152° 40' E, 27 January 1998, P. D. Perkins (1 MCZ); Dorrigo N. P., south slope Dome Mt. , subtropical rainforest, wet leaves and flood debris, forest stream, FMHD #86-682 , elev. 720 m, 30° 21' S, 152° 46' E, 28 December 1986, A. Newton & M. Thayer (778) (5 FMNH) .

Figures

FIGURES 19–22. Hydraena, dorsal and lateral habitus of holotypes. —19. H. millerorum. —20. H. tenuisoror. —21. H. latisoror. —22. H. williamsensis.

FIGURES 27–28. Hydraena williamsensis, aedeagi. —27. Holotype. —28. Holotype (after Zwick 1977).

FIGURES 23–26. Aedeagi of holotypes. —23. H. porchi. —24. H. millerorum. —25. H. tenuisoror. —26. H. latisoror.