Key to species (males) of Leptogaster Meigen, 1803 from Siberia (Russia)

1. Wings hyaline....................................................................................... 2

– Wings darkened proximally......................................................... L. fumipennis Loew, 1871

2. Mystax with 6–8 macrosetae............................................................................ 3

– Mystax with more than 9 macrosetae..................................................................... 4

3. Scape black at base. Scutellum with 4 short apical setae. Hypopygium equal or narrower than last abdominal segment in dorsal view.............................................................................. L. bivittata Lehr, 1975

– Scape reddish yellow. Scutellum without apical setae. Hypopygium wider than last abdominal segment in dorsal view..................................................................................... L. stackelbergi Lehr, 1961

4. Mystacal macrosetae arranged in more than one row......................................................... 5

– Mystacal macrosetae (12–14) arranged in one row at lower facial margin..................... L. nartshukae Lehr, 1961

5. Scape and pedicel or only pedicel reddish yellow. Postocular macrosetae white, yellow or partly black................. 6

– Scape and pedicel dark brownish. Postocular macrosetae black................................................. 7

6. Hind femur with a dark longitudinal stripe laterally, which is broader on apical third. Mystax with more than 15 macrosetae. Postocular macrosetae white or yellow. Hypopygium black.................... L. cylindrica cylindrica (De Geer, 1776)

– Hind femur with a dark brown ring on apical third. Mystax with 10–15 macrosetae. Postocular macrosetae mostly black. Hypopygium reddish yellow, epandrium black at the top.............................. L. guttiventris Zetterstedt, 1842

7. Mystax with more than 20 macrosetae. Hind femur and tibia with a dark longitudinal stripe laterally. Sternites reddish at posterior margin. Hypopygium partly reddish yellow............................ L. cylindrica hispanica Meigen, 1838

– Mystax with 9–14 macrosetae. Hind femur yellow with a dark brownish spot on distal part. Hind tibia dark brownish almost entirely. Sternites black. Hypopygium black................................................. L. nikiforovi sp. nov.