Key to the species of Prochyliza

1. Pedicel unusually elongate, in male twice (Fig. 4 A), in female equally (Fig. 4 B), as long as flagellomere (Nearctic).......................................................................................... P. xanthostoma Walker

- Pedicel normal, not or scarcely half as long as flagellomere in either sex (Fig. 4 C, D)............................... 2

2. Lower quarter to three quarters of frons orange, higher part shining black (Fig. 5 A–C).............................. 3

- Frons light orange to brownish black, but always uniformly coloured from lunula beyond anterior ocellus (Fig. 1 B, D).... 7

3. Front coxa pale yellow (Fig. 5 A)........................................................................ 4

- Front coxa brownish black (Fig. 5 B, C)................................................................... 6

4. Gena yellow, lower two- to three quarters of frons orange (Fig. 5 B). Mid femur and tibia yellow. Hind femur and tibia partially darkened. Males with posterior margin of sternite 5 straight. Male epandrium without a pair of distinct horn-like spines arising on lower half of posterior margin (Nearctic)............................................. P. brevicornis Melander

- Gena black, only lower quarter or less of frons orange (Fig. 5 C). Both mid and hind femora and tibiae either yellow or black. Males with posterior margin of sternite 5 strongly emarginated (unknown in P. a z t e c a). Male epandrium with a pair of distinct horn-like spines (Fig. 5 D) arising on lower half of posterior margin (unknown in P. azteca)........................... 5

5. Mid and hind femora and tibiae entirely yellow. Margins and fringes of calypteres white (Neotropical)... P. a z t e c a McAlpine

- Mid and hind femora and tibiae mostly black. Margins and fringes of calypteres brownish (Neotropical)... P. i n c a McAlpine

6. Mid and hind tibiae entirely yellow. Anepimeron pruinose along ventral margin above katepisternal seta. Mid tibia and hind coxa of male not ornamented (Nearctic).......................................... P. nigricoxa (Melander & Spuler)

- Mid and hind tibiae mostly blackish. Anepimeron glossy on ventral margin above katepisternal seta. Tibia of male with a brush of long, yellowish hairs at apex on posteroventral surface (Fig. 5 E). Hind coxa with a comb of short, stout setae (Holarctic)...................................................................................... P. lundbecki (Duda)

7. Front coxa entirely yellow to almost completely darkened (Fig. 1 A, B; Fig. 4 D). Mid and hind legs entirely yellow (Fig. 1 A); some individuals with mid and hind femora and tibae more or less darkened (Fig. 1 B). Male and female abdominal sternites with rounded margins (Fig. 2 A, B; Fig. 3 B, D); in males the anterior margins are usually emarginated and the posterior margin of sternite 5 is sinuate (Fig. 2 A, B) (Holarctic and Neotropical)............................... P. nigrimana (Meigen)

- Front coxa completely darkened (Fig. 4 C). Legs darkened (Fig. 6 A, B). Male and female abdominal sternites quadrangular, with straight margins, including the posterior margin of sternite 5 (Fig. 2 D, E; Fig. 3 A, C), only the anterior margin of sternite 2 is emarginated (Fig. 6 B) (Palaearctic)................................................ P. georgekaplani sp. nov.