Ephydrini Zetterstedt

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 : 228-229

Tribe Ephydrini Zetterstedt

Ephydrini Zetterstedt 1837: 48 (as Ephydrinae ). Type genus: Ephydra Fallén 1810 .— Wirth and Stone 1956: 45 [first use as a tribe].— Simpson 1979: 99–107 [life histories].— Olafsson 1991: 44–54 [relationships among Palearctic genera].— Mathis et al. 2025: 1–42 [phylogeny, taxonomy at generic level].

Halmopotini Canzoneri and Meneghini 1974: 147 (as Halmopotinae). Type genus: Halmopota Haliday 1856 .— Zatwarnicki 1992: 65–119 [synonymy, phylogeny, and classification].

Diagnosis: Specimens of Ephydrini may be distinguished from other Ephydridae by the following combination of character states.

Adult: Head: Mesofrons subquadrate, slightly wider posteriorly, with shiny, metallic luster; frequently with convergent, interfrontal setae inserted near anterior margin of mesofrons; dorsum of interfoveal hump usually shiny, with metallic luster, concolorous with mesofrons; fronto-orbital setae lateroclinate, 2 or more; face protruding, setulose to densely pilose, marginal setae larger; dorsum of interfoveal hump sometimes shiny; eye bare, usually as long as high, oval, and generally oriented obliquely to plane of epistoma; gena high, bearing a large genal seta and evenly covered with smaller setae; facial setae along oral margin usually dense and long; oral opening large, gaping, usually concealing clypeus.

Thorax: Dorsocentral setae 4–5 (1+3, 2+3), some setae sometimes weakly developed, the posteriormost seta displaced laterally from alignment of others; intrapostalar seta well developed, at least equal to 1/2 length of postalar seta; postsutural supra-alar seta well developed, subequal to postalar seta; notopleuron sparsely setulose; proepisternum setulose; prosternum setose, usually more evident along posterior margin near forecoxae; anepisternum bearing 1 large seta near middle along posterior margin, several smaller setae or setulae may also be present; anepimeron, meron, and metapleuron bare of setae; hindcoxal strap setose; pulvilli rudimentary or lacking; tarsal claws shallowly curved and usually elongate; costal vein extended to vein M 1; vein R 2+3 long, terminating at approximately same distance from vein R 4+5 as tip of vein M 1 is from vein R 4+5.

Abdomen: Male with 5 visible abdominal tergites; tergite 5 distinctly trapezoidal or triangular. Male terminalia: Epandrium in posterior view with symmetrical, ventral projections. Female with 6, sometimes 7, visible tergites, tergite 5 subtrapezoidal, not triangular.

Third-Instar Larva: Mouthhooks not joined together basally, each mouthhook spatulate and dentate marginally; anterior spiracles with 2–8 marginal papillae; posterior spiracles borne distally on bifid, retractile respiratory tube, tube 1/3–1/6 total body length; spiracular caps each bearing 4 spiracular openings (or series of openings), openings slit-like, oval, each bordered basally by hydrofuge interspiracular process; segments 5–12 with ventral prolegs bearing crochet-like spines in well-defined rows; dorsal patterns composed of flattened spines usually present; if prolegs and dorsal patterns absent, then spiracular openings subdivided and spiracular caps elongate.

Distribution.—Except for Arctic and Antarctic extremes, species of Ephydrini occur worldwide, although with unequal representation. Australia and New Zealand, for example, have species of Ephydrella (12 species) and Setacera Cresson (1 species) but no other genera. The South American fauna, reviewed in Mathis and Marinoni (2016), is comparatively much richer and comprises five genera: Austrocoenia Wirth (1 species), Neoephydra Mathis (18 species), Notiocoenia Mathis (3 species), Paraephydra Mathis (2 species), and Setacera (2 species). Aside from Setacera , the other Neotropical genera are endemic to the Region. Paracoenia (9 Species) and Coenia Robineau-Desvoidy (7 Species) are only known from the Northern Hemisphere in both the Old and New Worlds. The following genera are endemic to the Nearctic Region: Calocoenia Mathis (2 species), Dimecoenia Cresson (3 species), and Cirrula Cresson (4 species). Ephydra Fallén (33 Species) and Setacera (15 species) range more widely with both genera occurring in the New and Old Worlds, although Ephydra is largely lacking from the Neotropics with only two species occurring in Mexico and on some Caribbean islands. Halmopota Haliday (11 species) is found widely in much of the Old World except for the Afrotropics, and no congeners are known from the New World.

Discussion.—Available evidence, mostly morphological features, indicates that the tribe Ephydrini is monophyletic, as characterized above ( Costa et al. 2024, Mathis et al. 2025). Worldwide, the tribe comprises 13 genera and 118 species, including the new species described herein ( Mathis and Zatwarnicki 1995 and electronic updates).

Perhaps some of the disproportionate distributions noted above reflect taxonomic error. In the late 1970’s, for example, soon after WNM arrived at the Smithsonian Institution, he once showed George Steyskal without further comment a spot plate with the male terminalia of an Ephydrella species from New Zealand, and George quickly suggested that these structures represented an undescribed species of Dimecoenia . Steyskal (1970) had recently revised Dimecoenia and knew the morphology of these structures well. Was George correct? Are Ephydrella and Dimecoenia closely related?

To better resolve these and similar questions, Mathis et al. (2025) recently published a phylogenetic study of Ephydrini that was based on morphological characters and that also included the revised taxonomic classification and generic synopsis that were based on this cladistic analysis.