Parahyadina Tonnoir and Malloch

Mathis, Wayne N. & Zatwarnicki, Tadeusz, 2019, Revision of the Shore-fly Genera Parahyadina Tonnoir and Malloch and New Zealand Hyadina Haliday (Diptera: Ephydridae), Zootaxa 4623 (3), pp. 401-440 : 406-409

Genus Parahyadina Tonnoir and Malloch

Parahyadina Tonnoir and Malloch 1926: 17 . Type species: Parahyadina lacustris Tonnoir and Malloch 1926 , original designation.— Harrison 1959: 232–233 [fauna of New Zealand].— Mathis 1989: 646 [Australasian/Oceanian catalog].— Mathis & Zatwarnicki 1995: 209 [world catalog].— Zatwarnicki & Ryczko 2014: 502, 510–513 [description, phylogeny].

Diagnosis. Parahyadina is distinguished from other genera of the tribe Hyadinini by the following combination of characters: Adults, small to moderately small flies, body length 1.35–2.40 mm.

Head. Mesofrons and vertex with circular very sparse microtomentose area with denser microtomentum around ocelli; anterolateral frons with dense microtomentose triangle, darker in coloration than mesofrons; fronto-orbital plate dark colored, bare or with dense pale microtomentum; frons bare or with sparse to dense microtomentum. Arista bare or with short hairs, hairs no longer than basal aristal width. Face moderately produced medially; facial background generally similar to frons but with lighter colored silvery white microtomentum extended to gena; medially along parafacial, a band with sparse or no microtomentum extending lateroventrally below gena; marginal facial setulae in 2 rows. Gena concolorous with ventral parafacial plate; postgena and occiput concolorous with gena, sometimes with sparse microtomentum, and sometimes stripes of denser microtomentum across postgena and occiput, contiguous with lateral thoracic stripe pattern. Chaetotaxy: ocellar seta well developed, divergent, proclinate; pesudopostocellar seta minute, divergent, proclinate; usually 1 well-developed, lateroclinate fronto-orbital seta; both medial and lateral vertical setae well developed; facial setae minute, in 2 rows, medial row; genal setae minute, numerous along ventral genal margin. Antenna brown to dark yellowish brown; scape brown, pedicel brown, basal flagellomere darker in color dorsally; scape with row of setulae along distal ventral margin; arista filamentous with very minute dorsal branches distally. Proboscis with 2 pseudotracheae; cibarium with dispersed medial sensillae, posterior sensillae lacking, lacinia bar-like, sinuous in lateral view, tapered distally; maxillary palpus dark brown; prementum dark brown.

Thorax. Mesonotum bare or with sparse to dense microtomentum, often marked with distinct vittae, background pale brown to dark brown, microtomentum yellowish silver or silvery white. Scutellum trapezoidal with posterior margin slightly rounded, dorsally concolorous with posterior margin of mesonotum, lateral margin sometimes with denser microtomentum; postpronotum with silvery gray microtomentum; pleura often paler than mesonotum, with striped pattern of silvery gray microtomentum contiguous with microtomentum pattern of gena and occiput; anepisternum brown with sparse to dense microtomentum, often striped; katepisternum brown with sparse to dense microtomentum; subscutellum brown covered with sparse to dense microtomentum; anatergite brown covered with sparse to dense microtomentum. Chaetotaxy: acrostichal setulae minute, in single row; 1–2 prominent postsutural dorsocentral setae; 1 prominent supra-alar seta; only posterior notopleural seta present, inserted dorsomedially from notopleural suture; 1 anepisternal seta much reduced, hair-like, inserted along posterior margin at midheight; katepisternal setulae minute inserted dorsomedially; 2 scutellar setae. Wing: Costa long, extended to the vein M; costal section II less than twice length of section III; costal ratio variable but usually about 1.0; M vein ratio 0.23–0.39. Legs dark brown, shiny with sparse yellowish silver microtomentum. Halter knob yellowish white.

Abdomen. Tergites brown to dark brown; partially bare, and with anteriormost tergites more densely covered with microtomentum, with setal rows along margins; usually tergites 3 and 4 elongate. Male terminalia: Epandrium with surstyli fused at ventral margin, bearing setulae; cerci usually densely setulose; ventral margin of surstylus sometimes with distinctive setal patterns; gonites fused with hypandrium, often bearing 2 tiny, spine-like setulae; hypandrium narrow, U-shaped.

Remarks. Tonnoir and Malloch (1926) accorded generic status to Parahyadina based on the moderate to welldeveloped, lateroclinate, fronto-orbital seta. Otherwise, the overall habitus of the included species is similar to typical species of Hyadina with the exception, ironically, of species of Hyadina from New Zealand.

As noted previously, only a single species, P. lacustris Tonnoir and Malloch , was described before this study. Herein, we add ten more species. In general, the species of Parahyadina are very similar to each other, and determination of species can often only be accurately done by observing structures of the male terminalia. These structures, fortunately, are distinctive and not only enable identification of species but are a primary source of character data for determining phylogenetic relationships. These structures are fully illustrated to facilitate identification.