Ephydrini

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, intrafrontal 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 protrudent, 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, terminated 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, 5th tergite distinctly trapezoidal or triangular; female with 6, sometimes 7, visible tergites, 5th tergite 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 Cresson 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).