Ephydra Fallén, 1810

Mathis, Wayne N. & Sepúlveda, Luciane Marinoni and Tatiana A., 2025, Phylogeny and taxonomy of the shore-fly tribe Ephydrini with comments on related tribes in Ephydrinae (Diptera: Ephydridae), Zoologia (e 24044) 42, pp. 1-42 : 18-19

Ephydra Fallén, 1810

Ephydra Fallén 1810: 22 (feminine; type species: Ephydra riparia Fallén , by subsequent designation [ Curtis 1832: plate 413]). – Wirth 1968: 22 [catalog of South American species]; 1971: 357–377 [review of New World species, figures of male terminalia]; 1975: 11–44 [revision of Old World species]. – Zack et al. 1976: 205 [spatial isolation of species]. – Cash-Clark and Bradley 1994: 309–318 [larva of E. hians ]. – Mathis and Zatwarnicki 1995: 240–247 [world catalog]. – Mathis and Marinoni 2016: 88–97 [revision of Neotropical species]. – Krivosheina and Ozerov 2021: 345–360 [Russian fauna]. – Yakovleva et al. 2024: 360–375 [biology and immature stages of E. riparia ].

Diagnosis. Ephydra is distinguished from other genera of Ephydrini by the following characters:

Head: Lateroclinate, fronto-orbital setae 3, well developed, subequal; development of cruciate, interfrontal setae variable, either with one well-developed pair or weak to lacking; basal flagellomere simple, lacking secondary seta inserted below arista on lateral surface; arista variable, subpectinate to macropubescent, if subpectinate, basal thickening extended about 1/3 of aristal length, if macropubescent, basal thickening extended over 1/2 of aristal length; antennal groove distinct but not deeply impressed.

Thorax: 5 (1+4) well-developed; dorsocentral setae; presutural supra-alar seta present; intrapostalar seta present; supra-alar seta present; disc of scutellum generally concolorous with posterior portion of scutum. Costal vein ratio 0.24–0.40; M 1 vein ratio 0.61–0.81. Tarsal claws long, although length variable, and nearly straight; pulvilli greatly reduced or absent.

Abdomen: Structures of male terminalia considerably modified depending on subgenus and species group (see appropriate diagnosis of subtaxon for further details). Female terminalia: Female ventral receptacle with operculum small, trapezoidal in shape; extended process relatively large, C-shaped, length 2–3 times width of operculum.

Distribution. This speciose genus occurs primarily in temperate regions of the world as follows: New World. Widespread mostly in the Nearctic Region but extended into the northern Neotropical Region (12°– 65°N): Canada (just south of the Great Bear Lake), southward into Mexico (Oaxaca) and the West Indies (Dutch West Indies). Old World. Widespread, mostly in the Palearctic and Afrotropical (temperate) regions but extended into the northern Oriental Region: Norway to Japan, southward to the Canary Islands, South Africa, across southern Asia ( Afghanistan, Iran, and Tibet) to Japan and China.

Remarks. Wirth (1971, 1975) published excellent revisions of Ephydra on a worldwide basis, and his two papers should be consulted for a more detailed discussion of the natural history and for identification of extralimital species. Our treatment is essentially a synopsis of Wirth’s valuable studies, although with some modifications. Krivosheina and Ozerov (2021) recently produced an excellent review of the Russian fauna. Ephydra is the most speciose genus in the tribe Ephydrini with 34 species, and these are classified into two subgenera, Ephydra and Halephydra . The subgenus Ephydra is further divided into species groups. The subgenera and species groups are characterized and identified in the following key.