Ephydrella Tonnoir and Malloch

Mathis, Wayne N. & Zatwarnicki, Tadeusz, 2025, A review of Ephydrella Tonnoir and Malloch from the New Zealand subregion (Diptera: Ephydridae) with description of a new species, Zootaxa 5673 (2), pp. 227-251 : 229-231

Genus Ephydrella Tonnoir and Malloch

Ephydrella Tonnoir and Malloch 1926: 6 (as a subgenus of Ephydra ). Type species: Ephydra novaezealandiae Tonnoir and Malloch 1926 , original designation.— Cresson 1935: 354 [generic status].— Miller 1950: 111 [catalog of New Zealand Diptera ].— Harrison 1959: 244–249 [fauna of New Zealand].— Marshall and Wright 1974: 301–318 [ultrastructure of hindgut].— Bock 1987: 155–166 [revision of Australian species].— Mathis 1989: 647–648 [Australasian/Oceanian catalog].— Mathis and Zatwarnicki 1995: 247–248 [world catalog].— Mathis et al. 2025: 20–21 [taxonomy at generic level].

Mydaezealandia Salmon 1937: 359 . Type species: Mydaezealandia glauca Salmon 1937 (= Ephydrella spathulata Cresson 1935 ), original designation.— Salmon 1950: 2 [synonymy].

Diagnosis: Ephydrella is distinguished from other genera of the tribe Ephydrini by the following combination of characters: Medium-sized to large shore flies, body length 3.30–6.00 mm.

Head: Frons with shiny, metallic mesofrons, parafrons relatively dull, appearing somewhat “membranous”; 2 well-developed, lateroclinate fronto-orbital setae; cruciate interfrontal setae lacking; paravertical setae not evident; medial and lateral vertical setae well developed. Basal flagellomere lacking a lateral seta; arista long, almost double length of basal flagellomere, basal half somewhat swollen; dorsal aristal branches not evident, at most arista appearing macropubescent. Face with larger setae at lateral and oral margins; 1 large genal seta. Cibarium ( Fig. 1 ) 2.3 higher than wide, its dorsal portion W-shaped with long lateral processes; medial sensillae arranged in a sinuous line, its number about 40; posterior sensillae absent.

Thorax: Mesonotum dark colored, brown to metallic dark green or blue, similar to frons, with longitudinal light gray stripes in area of acrostichal tracks, scutellum triangular, posterior angle rounded, relatively acutely angulate, or narrowly truncate. Chaetotaxy: 1 well-developed pair of prescutellar acrostichal setae, otherwise as setulae; 4 (1+3) or 5 (1+4) well-developed dorsocentral setae, sometimes these appreciably reduced, posterior seta displaced laterally; 1 postpronotal seta; 1 presutural supra-alar seta; 1 supra-alar seta; 1 postalar seta; 2 lateral scutellar setae; prosternal setulae sparse on at least posterior portion; anepisternum with 1 long seta; katepisternum with 1 long, dorsoclinate seta. Wing generally hyaline; R stem vein bare above; costal vein ratio 0.23–0.25; M 1 vein ratio 0.68– 0.76. Male hindfemur not differing markedly from fore- or midfemur, lacking stout setae; male hindtibia lacking tuft of setulae; male hindtarsi cylindrical, normal; pulvilli much reduced or absent; tarsal claws long and nearly straight.

Abdomen: Male with5visible tergites,female with6–7;coloration similar to that of notopleuron,often submetallic but with varying levels of microtomentum. Male terminalia: Symmetrical, epandrium higher than wide, bearing prominent surstyli, these often elongate, shape species specific; a ventromedial, short, triangular process (lacking in E. bicolor ) between surstyli, process from more slender, lateral processes, process with a medial fissure; phallus in lateral view cylindrical, moderately slender, base with more sclerotized, distinctly curved process; phallapodeme in lateral view elongate, keel usually quite distinct, either apices rod-like, slender; postgonite+hypandrium sheathing phallus laterally and ventrally, usually longer than wide, variously shaped, but usually acutely pointed apically; subepandrium narrow band that arches over base of phallus; hypandrium shallowly v-shaped, angle very obtuse. Female terminalia: Female ventral receptacle with operculum variable in size from small papilla-like to large and helmet-like ( Figs. 2–3 ) with the width of the operculum slightly greater than height of extended process; sternites comprising the egg guide bearing 2 pairs of strong setae.

Natural history: Bock (1987) observed that larvae of some Australian species are associated with marine algae of the genus Cladophora . Some New Zealand congeners are associated with the effluent of hot springs, probably feeding on the associated algae.

Hughes et al. (2004: 838, 840), over 10 years ago, reported that two species of Ephydrella , E. aquaria and E. novaezealandiae , were parasitized by the fungus Stigmatomyces ephydrae Mercier & Poiss (Ascomycota: Laboulbeniales ).

Distribution: Ephydrella occurs on Australia and New Zealand.

Remarks: Ten species have been described in Ephydrella thus far, all from Australia and New Zealand, and herein, we add an 11 th species, E. bicolor sp. nov.

The shape of the surstylus and its relative length compared to the length of the medioventral process is used extensively to identify species of Ephydrella .

Figures

FIGURES 1–3. Anatomical structures of Ephydrella assimilis (Tonnoir & Malloch). 1. Cibarium, posterior view. 2. Female ventral receptacle, posterior view. 3. Same, lateral view. Scale bar = 0.05 mm.