Genus Discomyza Meigen

Discomyza Meigen 1830: 76 (feminine). Type species: Psilopa incurva Fallén 1823, by monotypy.─ Cresson 1939: 1 –6 [review].─ Mathis and Zatwarnicki 2005: 431 –443 [revision of New World fauna].─ Zatwarnicki and Mathis 2007: 241 – 266 [revision of Palearctic fauna].

Diagnosis. Moderately small to moderately large shore flies, body length 2.2–4.5 mm; generally black colored species. Face generally shiny, mostly bare of microtomentum, but conspicuously, transversely rugose, and with some vertical lines; 4–5 moderately-developed facial setae; arista pectinate, bearing 5–11 dorsal rays; frons rectangular, wider than long, mostly bare, shiny; intrafrontal setae absent; only reclinate fronto-orbital seta well developed, 2 proclinate setae evident but much smaller than reclinate seta, inserted anterior of reclinate seta; ocellar setae well developed; pseudopostocellar setae usually weakly developed, divergent and very slightly proclinate; both lateral and medial vertical setae well developed, above antennae a group (3–6) of small setulae, not visible by typical resolution of dissecting microscope; palpus black. Thorax: Scutum uniformly black or with whitish pattern, subshiny or dull; scutellum more or less trapezoidal (Figs. 46, 59). Prescutellar acrostichal setae lacking; presutural supra-alar seta evident but not well developed; postsutural supra–alar seta generally lacking; postalar seta 1; scutellar disc moderately setulose; basal scutellar seta over 1/2 length of apical seta; anepisternum with 2 large setae at posterior margin; katepisternum with 1 large setae. Halter with knob white to yellowish. Wing generally with some faint infuscation, often with distinct pattern along anterior margin and subapical and/or apical transverse bands; vein R2+3 well separated from costa, moderately long; R stem vein bearing 2–4 setulae dorsally; crossvein dm-m straight or slightly arcuate. Legs robust; forefemur bearing anteroventral comb-like setulae. Abdomen: Male terminalia: epandrium heavily sclerotized, generally of two kind of shapes: wide with high cercal cavity or narrow with short cercal cavity; pregonostylus at ventral margin of epandrium, varying considerably in shape; postgonostyli symmetrical or asymmetrical, generally elongate, if asymmetrical then right postgonostylus usually longer; medandrium broadly U-shaped; aedeagus tubular, elongate, wider basally; pre- and postgonite separated; pregonite short, bearing 2 apical setulae; hypandrium as shallowly pocket-like sclerite.