Austrocoenia Wirth

Mathis, Wayne N. & Marinoni, Luciane, 2016, Revision of Ephydrini Zetterstedt (Diptera: Ephydridae) from the Americas south of the United States, Zootaxa 4116 (1), pp. 1-110 : 8-10

Genus Austrocoenia Wirth

Austrocoenia Wirth 1970: 3 [type species: Austrocoenia aczeli Wirth 1970 , original designation].— Mathis 1980: 4 –7 [revision].—Lizarralde de Grosso 1989: 59 [fauna of Argentina].— Mathis and Zatwarnicki 1995: 235 [world catalog].

Diagnosis. Austrocoenia is distinguished from other genera of Ephydrini by the following combination of characters: Medium-sized to large shore flies, body length 3.65–5.10 mm; coloration generally gray; wing mostly hyaline; setae generally reduced.

Head: Mesofrons conspicuously setulose, completely microtomentose, dull, lacking large setae, cruciate or otherwise, parafrons more sparsely microtomentose; lateroclinate fronto-orbital setae 2; medial and lateral vertical setae both well developed; paravertical setae either reduced or lacking; antenna short; basal flagellomere lacking a lateral seta; basal flagellomere subequal in length to that of pedicel from dorsal view; arista short, only slightly longer than length of basal flagellomere, basal 2/3 thickened; antennal grooves deeply impressed; face long, distinctly protuberant anteriorly; facial setae small, setula-like; eye subspherical, slightly higher than wide; gena mostly bare, lacking a prominent seta, high, gena-to-eye ratio at least 0.60; maxillary palpus well developed.

Thorax: Acrostichal setae in 2 rows, these extended posteriorly to base of scutellum; well-developed, prescutellar, acrostichal seta 1, inserted slightly laterad of other acrostichal setulae; well-developed, dorsocentral seta 1, inserted near base of scutellum, with 3–4 larger setae along dorsocentral tract; postpronotal setae 1–2, these subequal in length to presutural supra-alar seta; postsutural supra-alar seta reduced or lacking; disc of scutellum bare; lateral scutellar setae 2; prosternum bare. Wing normally developed, mostly hyaline; costal margin with short spinelike setae; costal vein long, extended to vein M; R stem vein bare dorsally. Pulvilli well developed; tarsal claws short and distinctly curved; hindfemur of male not differing markedly from fore- or midfemur, lacking stout setae as above; hindtibia of male lacking tuft of setulae; hindtarsi of male cylindrical, normal.

Abdomen: Tergites generally setose, setae along margins larger. Males with 5 visible segments, with tergite 5 longest, trapezoidal, broadly truncate posteriorly; females with 7. Male terminalia: Cercus of male terminalia elongate, fused ventrolaterally with epandrium; surstylus evidently fused with ventral margin of epandrium; gonite plate-like; aedeagus greatly reduced; female ventral receptacle with operculum subtrapezoidal, asymmetrical, extended process more or less C-shaped.

Distribution. Austrocoenia is endemic to southern South America (Patagonia, between 49°–52°S).

Discussion. Austrocoenia is a monotypic genus and is somewhat of an anomaly. Due to the autapomorphic condition of several of its characters, we have not succeeded in discovering evidence that would indicate a phylogenetic relationship with other generic level taxa of Ephydrinae . We have tentatively placed Austrocoenia near the Paracoenia-Calocoenia lineage because adults have five dorsocentral setae. But even this character state is autapomorphic, as the anterior pairs of setae are reduced and are only slightly larger than surrounding setae.

Wirth (1970: page) was also perplexed by his new genus, noting that although the Austrocoenia is clearly a member of the subfamily Ephydrinae , “...it is not closely allied with any known genus. It appears to be closest to Coenia Robineau-Desvoidy , a Holarctic genus, which it resembles to a slight extent in the presence of four pairs of dorsocentral setae and curved tarsal claws. Otherwise, its similarities are diverse and rather remote.. Austrocoenia is doubtless an annectant form surviving and modified from a very early offshoot of the Ephydrinae .”