Ephydrini

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 : 6-7

Tribe Ephydrini Zetterstedt

Ephydrini Zetterstedt 1837: 48 [as Ephydrinae ].— Wirth and Stone 1956: 45 [first formal use and diagnosis as a tribe].— Mathis and Zatwarnicki 1995: 235 –254 [world catalog].

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; vein R2+3 long, terminating at approximately same distance from vein R4+5 as tip of vein M is from vein R4+5. Abdomen: Male with 5 visible abdominal tergites, tergite 5 distinctly trapezoidal or triangular; 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 slitlike, oval, each bordered basally by hydrofuge interspiracular process; segments 5–12 with ventral prolegs bearing crochetlike 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.

Discussion. Larvae of most Ephydrini are easily recognized by their elongate respiratory tube, ventral prolegs, and dorsal pattern of spines. The larvae of Dimecoenia are exceptional in not having conspicuous prolegs but can be distinguished by the shape of their mouthparts, the unique structure of the posterior spiracles, and their habitat distribution (salt marshes).

The monophyly of the tribe Ephydrini is well established, being based on the following synapomorphies: 1. Setal vestiture of prosternum: In members of Ephydrini , the prosternum is setulose to setose, especially ventrally and posteriorly around the coxal cavities, but usually more extensively. The generalized condition in the family is for the prosternum to be bare of setae. 2. Hindcoxal strap: The hindcoxa has a strap that extends around the posterior side. This strap bears four or five setae in members of Ephydrini . Elsewhere in the family the strap is bare. 3. Pulvilli: With few exceptions in the family, the pulvilli are evident as conspicuous pads beneath the tarsal claws. In members of Ephydrini , however, the pulvilli are either rudimentary or are apparently lacking. 4. Tarsal claws: The tarsal claws are shallowly curved and are usually elongate in members of Ephydrini . The generalized condition is for claws to be conspicuously curved and short. 5. Larval prolegs: With the exception of a secondary loss in Dimecoenia , larvae of Ephydrini have prominent, ventral prolegs that bear crochets. These structures are an adaptation to the algal-mat habitat of the immatures of these flies and assist in grasping the substrate. The secondary loss of prolegs in larvae of Dimecoenia apparently occurred as the latter shifted back to a mud-shoreline habitat. Larvae of Dimecoenia have creeping welts, similar to those of other mud inhabiting Ephydridae ( Mathis and Simpson 1981) . 6. Habitat of immatures: The generalized habitat for the subfamily Ephydrinae is probably shoreline mud. This is the habitat of most species of Scatellini and Parydrini . However, members of Ephydrini have adapted to algal mats on the surface of both lentic and lotic water systems.

Although the tribe Ephydrini is undoubtedly monophyletic, its companion tribe, Scatellini , is not. Ephydrini are but one of several monophyletic lineages arising from the ancestral lineage that now comprises the concept of Scatellini ( Mathis 1979c, 1980).