Key to species of the genera of Pterogenia and Neohemigaster of the Eastern Palaearctic and adjoining areas of the Oriental Region

1. Tergite 5 much shorter than tergite 3, absent in female. Cell bm enlarged, usually 1.3–1.5 as long as bcu and 1.25–1.6 times shorter than discal medial cell. Face concave at least in its lower part................ Pterogenia and Neohemigaster ... 2

- Without this combination of characters........................................... other genera of Platystomatidae

2. Stem R vein (basal part of R before branch of humeral crossvein) covered by short black, rare yellow, setulae Pterogenia ... 3

- Stem R vein bare...................................................................... Neohemigaster ... 7

3. Scutellum entirely black............................................................................... 4

- Scutellum black with yellow marks........................................... Pterogenia luteipennis Bezzi, 1916

4. Mesonotum black; postpronotal lobe yellow anteriorly and laterally; yellow stripe along the upper margin of anepisternum, this stripe extends backward to the wing base. Brown spot between base of antenna and eye. Lunule yellow. Halter yellow. Wing—Fig. 2e.......................................................... Pterogenia hologaster Hendel, 1914

- Thorax unicolourous black; narrow longitudinal reddish stripe anteriorly at the ventral part of anepisternum. Other characters variable............................................................................................. 5

5. Wing with short prediscal black band (from apex of R1) and broad stigmatal band (from apex of Sc) merging at level of r-m (Fig. 3 e). Lunule dark brown. Dark brown spot between base of antenna and eye. Halter with brown knob............................................................................................. Pterogenia tenebrica sp. nov.

- Prediscal and stigmatal bands separate (Figs 4 a, 5e)......................................................... 6

6. Preapical transverse band (beginning from R2+3 apex) contiguous (Fig. 4 a). Lunule blackish brown. Halter yellow..................................................................................... Pterogenia hamifera Frey, 1930

- Preapical transverse band broken into 4 spots (Fig. 5 e). Lunule light yellow. Dark brown spot between base of antenna and eye absent. Halter with brown knob............................................... Pterogenia luctuosa Hendel, 1914

7. Face monochrome yellow, without spots................................................................... 8

- Face yellow, with brown or blackish brown spots........................................................... 9

8. Lunule yellow. Wing—Fig. 4b.......................................... Neohemigaster minuspicta (Hennig, 1940)

- Lunule black.......................................................... Neohemigaster monticola (Frey, 1964)

9. Lower part of occiput with brownish spot touching posterior margin of eye, above its inferior angle (Figs 1, 6, 7, 8)..... 10

- This brownish spot absent............................................................................ 15

10. Face with separate medial and two lateral spots, located in line (Fig. 6 d). Wing—Fig. 6e................................................................................................. Neohemigaster eurysterna (Hendel, 1914)

- Face medial spot sometimes indistinct (Fig. 7 d); if present, then forming triangle with lateral spots (Figs 1, 8)........... 11

11. Stigmatal transverse band includes r-m vein (Figs 1 e, 4c). Lunule and face between bases of antennae black. Mouth margin with single brown medial spot.......................................................................... 12

- Stigmatal transverse band doesn’t include r-m vein (Fig. 4 d, 7e, 8e). Lunule and face between bases of antennae yellow. Mouth margin with two brown lateral spots and often with one brown medial spot..................................... 13

12. Frons with brownish-black transversal band in anterior part. Scutellum with broad yellow bordering. Wing—Fig. 4c.......................................................................... Neohemigaster flavopicta (Hennig, 1940)

- Frons with two separate brownish-black rounded spots in anterior part, without transversal band (Fig. 1 d). Mesonotum with three longitudinal stripes. Wing (Fig. 1 e) with large isolated round spot on cell r4+5 above m-cu vein....................................................................................... Neohemigaster rectivena (Enderlein, 1924)

13. Scutellum with two brown longitudinal stripes on disk, these stripes don’t connect neither to base nor to posterior margin of scutellum. Face with two brown lateral spots; median facial spot absent. Mouth margin with two brown lateral spots and without medial spot (Fig. 7 d). Wing—Fig. 7e..................................... Neohemigaster angustifrons sp. nov.

- Scutellum black, yellow bordered or with yellow spot posteriorly. Face with three brown spots, forming triangle if connected (Fig. 8 d). Medial epistomal spot well developed (i.e., margin of peristomal cavity with three brown spots)............. 14

14. Scutellum with broad yellow bordering (Fig. 8 b). Abdominal tergites 2–5 yellow posteriorly; tergite 2 also yellow laterally. Cell r4+5 with 4 brown bands; prediscal band contiguous to darkening on r-m vein (Fig. 8 e)................................................................................................... Neohemigaster tetralineata sp. nov.

- Scutellum just with a yellow spot posteriorly. Only abdominal tergite 5 yellow posteriorly. Cell r4+5 with 3 brownish bands. Prediscal band broken into separate spots and not reaching r-m (Fig. 4 d)............... Neohemigaster ornata (Hennig, 1940)

15. Gena high; more than 0.4 (0.48–0.51) times as high as eye. Face with single medial spot; gena and postgena yellow (Fig. 9 c). Gena yellow setulose. Wing as on Fig. 9 e................................. Neohemigaster ussurica (Korneyev, 2001)

- Gena low, less than 0.4 (0.27) times as high as eye. Face with three black spots forming triangle if connected. Gena in its ventral part and postgena black (Fig. 10 c). Wing as on Fig. 10 e.......................... Neohemigaster antropovi sp. nov.