Gymnochthebius fontinalis, 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 fontinalis new species

(Figures 52, 53, 90)

Type Material. Holotype (male): Australia: South Australia: Elizabeth (Mound)

Springs , 7 km NW Coward Springs R.S., 29° 24' S, 136° 47' E, 14 May 1981, J. A. Forrest. Deposited in the SAMA. Paratypes: Same data as holotype (11 SAMA). Representative specimens to be deposited in MCZ and NPC .

Differential Diagnosis. Recognized by the rather flattened and parallel­sided form, the subtruncate elytral apices, and the dull, microreticulate and coarsely densely punctate pronotum. Sharing with G. nigriceps the anteriorly extended lateral hyaline border, the distinctive abdominal hydrofuge pattern where the hair­line forms a very discrete arc on the fifth ventrite, and the females having a spinose last tergite. Differing from G. nigriceps in having the pronotal disc more coarsely punctate, the dorsum less convex and more parallel­sided (Figs. 50, 52), the coloration, and in females the angulate last tergite. The male genitalia of the two species also show a relationship, but differ significantly in several features, including lobe and duct shapes, and the greater length in G. fontinalis (Figs. 51, 53).

Description. Size (length/width, mm) holotype: body (length to elytral apices) 2.04/ 0.82; head 0.33/0.48; pronotum 0.44/0.59; elytra 1.30/0.82. Form moderately elongate, comparatively longitudinally planar. Head and disc of pronotum piceous to dark brown, on pronotum grading to brown or light brown at margins; elytra light brown to testaceous. Dorsum dull, microreticulate and coarsely punctate.

Head comparatively flat, dull, markedly microreticulate, with moderately dense, short distinctive whitish setae; interocular foveae shallow; interocular tuberculi indistinct; basomedial fovea narrowly confluent with interocular foveae. Frontoclypeal suture deeply impressed, bisinuate. Clypeus midlength 0.5 apical width. Labroclypeal suture straight in dorsal view, evenly arcuate in anterior view. Labrum length:width 4:15, anterior margin straight or slightly emarginate, weakly reflexed.

Pronotum lateral hyaline border well developed, origin at anterior 0.33 of lateral depression, margin straight, then arcuate at posterior angles, very narrow around posterior margin; anterior margin of pronotum straight in midregion; each lateral depression with margin weakly arcuate from anterior angle, then emarginate before slightly obtuse posterior angle, lateral margin between anterior angle and hyaline border with short setae; lateral fossulae deep, microreticulate; pronotal disc transversely weakly convex; median groove rather shallow, narrow, constricted slightly past midlength, ended before margins, tapering at ends; anterior foveae deep, oblique, oval, wider than median groove, each separated from posterior fovea by width of anterior fovea; posterior foveae very slightly oblique, nearly parallel to median groove, deep, 1/2 as long as and twice as wide as median groove; posterolateral angles lacking impressions.

Elytra weakly transversely convex on disc, with six rows of punctures between suture and humeri; punctures round, separated from each other by 0.5–1.0x puncture width, each with a short recumbent seta; intervals flat or slightly rounded, moderately dull, width slightly greater than that of punctures; posterior declivity very gradual, summit at about midlength; striae 2 and 3 terminating into 4 at about apical 0.15; elytral explanate margin very narrow, without fringe of setae.

Metasternal glabrous area longer than wide (as 20:17), elongate oval, shining, sparsely punctate, convex in female, more nearly flat in male. Abdominal sternites 1–4 and part of 5 with hydrofuge pubescence; on 5 pubescence laterally and basally, forming very discrete arc­shaped non­pubescent area. Sixth ventrite posterior margin emarginate, in male strongly, in female weakly.

Aedeagus (Fig. 53): Length of main­piece 0.64 mm, tips of parameres slightly below tips of lobes; main­piece markedly elongated and slender between base and origin of parameres; lobes short compared to total length of aedeagus, not barbed but sometimes with extremely minute point on inner margin of ventral notch; ventral notch V­shaped, wide apically, margins not sinuate; dorsal notch U­shaped, wider proximally and slightly deeper; duct straight and gradually tapering in ventral aspect, weakly curved apically in lateral aspect; paramere setae clustered at and near apex, apical setae short, longest seta ca. 3x length of next longest.

Females have the explanate elytral margin about the same width as in males; the labrum is apicomedially weakly emarginate; the last abdominal tergite is sharply arcuate and has a prominent fringe of spine­like setae.

Etymology. Named in reference to the microhabitat.

Distribution. Currently known only from Elizabeth (Mound) Springs in central South Australia (Fig. 90).