Key to genera of Mythicomyiinae of the World

1. Antenna with style placed subapically on the second flagellomere (Fig. 1)........ 2

— Antenna with style placed apically on the second flagellomere (Fig. 2)............ ............................................. Mythenteles Hall & Evenhuis

2. Ambient vein complete; cell dm fairly short, closed apically Reissa Evenhuis & Baéz

— Ambient vein incomplete, stopping just beyond end of vein R4+5; cell dm much longer than wide or open apically.............................................. 3

3. Wing with keel­shaped and well developed anal lobe; vein separating basal cells not evident; eyes holoptic in males ... ( Mythicomyia)............................ 4

— Wing with anal lobe normal, not keel shaped; vein separating basal cells distinct, often well sclerotized; eyes dichoptic in males................................... 5

4. Males with secondary sexual character modifications on the legs (modified shapes of and notches in mid and/or hind legs and presence of pegs and large setae)............................................. Mythicomyia (Mythicomyia) Coquillett

— Males without secondary sexual character modifications of legs........................................................ Mythicomyia (Heterhybos) Brèthes

5. Wing with cell dm open, distal veins faint or effaced; head as wide or wider than thorax Nexus Hall & Evenhuis

— Wing with cell dm complete; distal veins not faint; head usually narrower than thorax............................................... Pieza Evenhuis, gen. nov.