Gymnochthebius angulonotus, 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 angulonotus new species

( Figures 5 , 6 , 77)

Type Material. Holotype (male): Australia: Queensland: Tinaroo Ck. Rd. via Mareeba , 17° 1' S, 145° 27' E, 21 October 1991, DeFaveri, Huwer, Storey. Deposited in

the QMBA. Paratypes (4): Australia: Queensland: Clohesy River , slow flowing stream, sandy banks, algal growth, half sun, riverine scrub, unfresh water, 16° 55' S, 145° 34' E, 22 December 1994, P. Zborowski (2 ANIC) ; N.Q., 15 km NE Mareeba, MDPI intercept trap site No. 25, flight intercept trap, 16° 56' S, 145° 32' E, 7 January–12 February 1985, Storey & Halfpapp (1 QPIM) ; same locality, 16° 56' S, 145° 32' E, 12 February–20 March 1985, Storey & Halfpapp (1 QPIM) . Representative specimens to be deposited in MCZ .

Differential Diagnosis. Recognized by the angulate anterolateral areas of the pronotum, the dark brown to piceous dorsum, the finely sparsely punctate and shining pronotum, the comparatively short pronotum and wide body, and the elytral intervals ca. twice as wide as the weakly striate­impressed series. This species has some resemblance to G. australis and G. setosus , which also have a setal fringe on the elytral margins, but differs in shape of the pronotum, color, and male genitalia form ( Figs. 2 , 4 , 6 ).

Description. Size (length/width, mm) holotype: body (length to elytral apices) 1.89/ 0.86; head 0.37/0.52; pronotum 0.41/0.67; elytra 1.33/0.86. Form moderately ovate, moderately convex. Color dark brown to piceous, dorsal surface shiny, non­microreticulate.

Head shiny, frons very finely sparsely punctate, sparsely pubescent; interocular foveae deep, pubescent; interocular tuberculi distinct; basomedial fovea narrowly confluent with interocular foveae. Frontoclypeal suture deeply impressed, bisinuate. Clypeus midlength slightly less than apical width, very sparsely punctate; pubescence very sparse on disc, slightly more developed laterally. Labroclypeal suture straight in dorsal view, evenly arcuate in anterior view. Labrum width twice length, anterior arcuate, apicomedially raised in form of very small tooth (male only).

Pronotum lateral hyaline border well developed, origin at base of lateral depression, arcuate to posterior angles, very narrow around posterior margin; anterior margin of pronotum markedly bisinuate, anterior angles produced more anteriorly than midline sclerotized part; each lateral depression with posterior angle produced to form small point, posterior margin concave, lateral margin setose, weakly arcuate; lateral fossulae shiny, deep, lacking microsculpture; pronotal disc moderately transversely convex, shiny, extremely finely sparsely punctate, each puncture with a recumbent seta; median groove deep, moderately wide, extending nearly to margins, tapering at ends; anterior foveae oval, deep, each separated from posterior fovea by 2 times length of anterior fovea; posterior foveae oblique, shallow, linear impressions with ill­defined margins, slightly less than 1/2 as long as and as wide as median groove; posterolateral angles lacking impressions.

Elytra moderately transversely convex on disc, with 6 rows of punctures in weakly developed striae between suture and humeri; intervals shiny, rounded, width 1.5–2x that of punctures; punctures round, separated from each other by about puncture width, each with a recumbent seta; summit of declivity near posterior one­third; sides of elytra nearly vertical in posterior 1/4, apices conjointly sharply rounded; stria 3 terminating into 4 at about apical 1/4; elytral explanate margin moderately wide, with distinctive fringe of setae.

Metasternal glabrous area oval, length equal width, shining, convex. Abdominal ventrites 1–3 and basally 4 with hydrofuge pubescence.

Aedeagus ( Fig. 6 ): Length of main­piece 0.28 mm, length to tip of parameres 0.31 mm; lobes relatively long and slender, each with a small subapical barb; notches wide, Ushaped, narrowing slightly apically, ventral notch slightly deeper than dorsal notch; duct truncate at apex; apical paramere seta elongate, ca. 2x length of next longest setae.

Females are similar to males in form of the elytral epipleuron; the apical margin of the labrum is arcuate.

Etymology. Named in reference to the angulate anterolateral areas of the pronotum.

Distribution. Currently known from three closely clustered localities in northern Queensland (Fig. 77).

Figures

FIGURE 2. Gymnochthebius australis. Aedeagus of lectotype.

FIGURE 4. Gymnochthebius setosus. Aedeagus of holotype.

FIGURE 5. Gymnochthebius angulonotus, holotype. Dorsal and lateral habitus.

FIGURE 6. Gymnochthebius angulonotus. Aedeagus of holotype.