Gymnochthebius wattsi, Perkins, 2005

Perkins, Philip D., 2005, A revision of the water beetle genus Gymnochthebius Orchymont (Coleoptera: Hydraenidae) for Australia and Papua New Guinea, Zootaxa 1024 (1), pp. 1-161 : 1-161

Gymnochthebius wattsi new species

( Figures 15 , 16, 80)

Type Material. Holotype (male): Australia: Victoria: 10 km NE Mirranatwa , small creek bed ­ drying pool, stony, dead leaves, dry sclerophyll forest, 37° 36' S, 142° 13' E, 12 October 1997, C. Watts. Deposited in the SAMA . Paratypes (41): Australia: New South Wales: Berry , 34° 46' S, 150° 42' E, 1–30 January 1968, C. Watts (4 SAMA) ; Tasmania: “3794” [no other data, no date], A. Simson (2 SAMA) ; St. Helens , 41° 20' S, 148° 15' E, 1–30 January 1962, C. Watts (1 SAMA) ; Victoria: 10 km NE Mirranatwa , small creek bed ­ drying pool, stony, dead leaves, dry sclerophyll forest, 37° 36' S, 142° 13' E, 12 October 1997, C. Watts (21 SAMA) ; Avon River, at Princes Hwy. bridge, Stratford , gravelly cobble­bank at edge of riffle of river, elev. 10 m, 37° 58' S, 147° 4' E, 19 September 1999, N. Porch (56) (1 ANIC) ; Holey Plains State Park, firedam on Crooke Track , fine sand and organics at the edge of a small firedam in dry sclerophyll forest, elev. 45 m, 38° 10' S, 146° 20' E, 16 April 2002, N. Porch (87) (12 ANIC) . Representative specimens to be deposited in MCZ, MVMA, NMW, NPC, and QMBA .

Differential Diagnosis. Recognized by the confluent anterior and posterior pronotal foveae, the shining dorsal reliefs, the moderately coarsely punctate pronotum, and the striate­impressed elytral series. This species shows some resemblance to G. semicylindrus , but is distinguished therefrom by the smaller size (ca. 1.75 vs. 1.86), the flatter body form, the confluent pronotal foveae, the arcuate lateral margins of the pronotum, and the slightly less coarsely punctate pronotum and elytra ( Figs. 15 , 17 ). The male genitalia of the two species also suggest a relationship, but in G. wattsi the duct is very large compared to the lobes, the lobes are rounded apically in ventral aspect, and the parameres do not extend beyond the tips of the lobes ( Figs. 16, 18 ).

Description. Size (length/width, mm) holotype: body (length to elytral apices) 1.75/ 0.75; head 0.33/0.44; pronotum 0.37/0.56; elytra 1.07/0.75. Form moderately ovate, moderately convex. Color dark brown to piceous, dorsal reliefs shining.

Frons moderately finely sparsely punctate, very sparsely pubescent; interocular foveae deep; interocular tuberculi distinct; basal midlongitudinal fovea confluent with interocular foveae. Frontoclypeal suture deeply impressed, bisinuate. Clypeus midlength:apical width as 7:13, more densely punctate laterally than medially, pubescence denser laterally. Labroclypeal suture straight in dorsal view, evenly arcuate in anterior view. Labrum length:width as 5:13; anterior margin arcuate, with low upturned apicomedian tooth. Maxillary palpomere 3 twice length of 4.

Pronotum lateral hyaline border well developed, origin at base of lateral depression, sharply arcuate, almost angulate, to posterior angles, very narrow around posterior margin; anterior margin of pronotum slightly arcuate in midregion; each lateral depression with posterior in form of right angle, lateral margin arcuate from anterior angle then shallowly emarginate before posterior angle; lateral margin with very short fringe of setae; lateral fossulae deep, lacking microsculpture; pronotal disc moderately convex, punctures on reliefs deep, moderately small and irregularly spaced; median groove deep, narrow, extending nearly to margins, constricted in midlength and tapering at ends, margins irregular, punctate; anterior foveae well developed, deep; posterior foveae oblique, linear impressions nearly 1/2 as long as and as wide as median groove; posterolateral angles with indistinct shallow impressions.

Elytra moderately convex on disc, sides nearly vertical in basal 0.5, with six rows of punctures in well developed striae between suture and humeri; each puncture with a recumbent seta that overlaps base of following seta; intervals rounded, slightly wider than striae, smooth and shining; posterior declivity gradual, summit slightly past midlength; explanate margin narrow, without fringe of setae.

Metasternal glabrous area length equal to or slightly greater than width (as 16:15), subrhomboidal, shining, convex. Abdominal ventrites 1–3 and basally 4 with hydrofuge pubescence.

Aedeagus ( Fig. 16): Length of main­piece 0.28 mm, parameres not extended beyond tips of lobes; lobes in ventral aspect apically rounded, not barbed, tips bent in oblique aspect; ventral notch V­shaped, widest apically, dorsal notch U­shaped, not as deep as ventral notch; duct very wide, ca. 2x width of lobes in lateral aspect, roundly, slightly expanded at tip; apical paramere seta elongate, ca. 2x length of next longest seta.

Females have the elytral explanate margin similar to that of males; the anterior margin of the labrum is weakly apicomedially emarginate.

Etymology. Named in honor of the water beetle taxonomist, Chris Watts.

Distribution. Currently known from southern New South Wales, southern Victoria, and Tasmania (Fig. 80).

Figures

FIGURE 15. Gymnochthebius wattsi, holotype. Dorsal and lateral habitus.

FIGURE 17. Gymnochthebius semicylindrus, holotype. Dorsal and lateral habitus.

FIGURE 18. Gymnochthebius semicylindrus. Aedeagus of holotype.