Gymnanthelius Perkins, 1997

Perkins, Philip D., 2004, A revision of the Australian endemic water beetle genus Gymnanthelius Perkins (Coleoptera: Hydraenidae), Zootaxa 585, pp. 1-39 : 5-6

Gymnanthelius Perkins, 1997

Gymnanthelius Perkins, 1997: 139 (type species Ochthebius hieroglyphicus Deane, 1933 )

Diagnosis. Recognized by the combination of the bilobate labrum with U­shaped apicomedian notch, the deep foveae of the frons, the wide, continuous lateral hyaline border of the pronotum, the angulate lateral process of the pronotum, the deep median groove and lack of posterior foveae of the pronotum, the details of the antennal pocket and exocrine secretion delivery system (see below) and, in males, the basally angulate last article of the mesotarsi, and the basic aedeagal structure.

Description. Body size ca. 1.48 mm to 2.10 mm, form elongate oval, moderately to very convex dorsally, head not or only weakly deflexed. Antennomeres nine (four + club), first slightly longer than club, second oval, third and fourth minute. Maxillary palpi short, penultimate article oval. Mentum emarginate anteriorly, angles sublobate and setose. Eyes large, not elevated. Labrum moderately large, anterior margin with U­shaped notch forming two lobes; U­shaped notch with many sensilla, each nearly attaining midline and with slightly expanded tip; labral lobes slightly larger in male, and slightly reflexed. Labroclypeal suture arcuate. Clypeus parallel­sided or slightly convergent anteriorly, anterior margin straight or only slightly arcuate, anterior angles each produced in tiny point. Ocelli narrowly separated from eyes. Frons with deep fovea medial to each ocellus; fovea very deep in center, becoming shallower posteriorly where arcuate toward midline, in most species foveae separated from each other posteriorly by basomedial longitudinal narrow low ridge or carina (in maxipunctus and tunicus foveae are not confluent with basomedial ridge).

Pronotum with deep midlongitudinal fovea and shallow pair of oval anterior foveae; posterior foveae absent, although punctures may be denser in these areas; lateral fossulae deep, lateral depressions moderately wide, produced as distinct angulate process where lateral fossulae meet lateral margin; anterior hyaline border wide, posterior hyaline border narrower, bisinuate; lateral hyaline border continuous from just behind anterior angles to posterior angles where confluent with posterior hyaline border, wide except at angulate process of lateral depression. Elytra punctation varying from ten rows of striate­impressed punctures, to completely randomly punctate. Metasternum varying from entirely hydrofuge pubescent to having moderately large glabrous basomedial area. Abdominal ventrites 1–4 hydrofuge pubescent, remaining ventrites with sparse setae; ventrites 1–2 with short spiniform setae intermixed with hydrofuge pubescence (microslide mount).

Legs stout and spinose; profemur with distal cluster of strong spines; male mesotarsi with last article markedly angulate at base.

Antennal pocket (terminology as in Perkins, 1997) hypomeral, wide, smooth except for anteromedial asperite hydrofuge area. Hypomeral, lateral, anterior, and posterior hyaline borders all well developed. Hypomeral antennal pocket setae short (relative to those of Ochthebius ), extending only slightly beyond the hh­border. Wet hypomeron small. Postocular area near posteroventral angle of eye with strongly microreticulate shelf that terminates in spiculate secretion area with exocrine pores. Spiculate margin continuous with trans­genal ridge. Adjacent to spiculate secretion area are about three specialized plumose secretion delivery setae, each with multiply branched tips. Genal hydrofuge strongly asperite; postocular area near delivery setae is rather sparsely pubescent and smooth. Periocular pores are present adjacent to the eye facets.