1 Prosternum clothed entirely with white to brownish silky hair-like setae ( Fig. 3D)..... R. ( Ctenempis) albopilosa Coquillett
- Prosternum bare...................................................................................... 2
2 Hind femur with pennate setae ventrally ( Fig. 9B)........................................................... 3
- Hind femur without pennate setae ventrally................................................................. 6
3 Thorax with grey pruinescence, with brown colouration beneath rows of acrostichals and dorsocentral setae.................................................................................... R. ( Pararhamphomyia) helleni Frey
- Thorax brown, without brown vittae...................................................................... 4
4 Robust species with darkly infuscate wings; acrostichals multiserial and scutum brown with pair of greyish vittae between acrostichals and dorsocentral setae................................... R. ( Dasyrhamphomyia) hovgaardii Holmgren
- Slender species with lightly infuscate wings; acrostichals biserial; scutum shiny.................................... 5
5 Hind tibia with simple setae only ( Fig. 51A)............................................... R. herschelli Malloch
- Hind tibia with pennate setae ( Fig. 56A)..................................................... R. laevigata Loew
6 Wing with basal costal seta............................................................................. 7
- Wing without basal costal seta.......................................................................... 14
7 Halter yellowish to white............................................................................... 8
- Halter brownish..................................................................................... 10
8 Scutum black subshiny beneath rows of dorsocentral setae; abdominal tergites shiny laterally............................................................... R. ( Eorhamphomyia) shewelli Sinclair, Vajda, Saigusa & Shamshev sp. nov.
- Scutum and abdominal tergites entirely pruinescent.......................................................... 9
9 Occiput with stout setae; dorsocentral setae multiserial; legs reddish, subshiny................ R. ( P.) simplex Zetterstedt
- Occiput without stout setae; dorsocentral setae uniserial; legs pale brown, not shiny................................................................................. R. ( P.) lymaniana Sinclair, Vajda, Saigusa & Shamshev sp. nov.
10 Scutellum with at most 3 pairs of marginal setae............................................................ 11
- Scutellum with more than 3 pairs of marginal setae......................................................... 12
11 Scutum dark brown; hind tibia with numerous anterodorsal and posterodorsal setae longer than width of tibia................................................................................................. R. setosa Coquillett
- Scutum dark, with greyish pruinescence; hind tibia with few dorsal setae, at most as long as width of tibia...................................................................................................... R. ( P.) hoeli Frey
12 Thorax and, usually, legs with grey pruinescence............................................................................................................ R. ( P.) petervajdai Sinclair, Vajda, Saigusa & Shamshev sp. nov.
- Thorax and legs brown, without grey pruinescence.......................................................... 13
13 Hind tarsomere 1 with several long dorsal setae longer than width of tarsomere; anal lobe of wing darker than wing tip....................................................................... R. ( P.) filicauda Henriksen & Lundbeck
13 Hind tarsomere 1 without long dorsal setae; anal lobe of wing similar to wing tip.................. R. hirtula Zetterstedt
14 Wing with cell bm greatly elongated with apex almost reaching wing margin, cell dm open and vein M 2 reduced (sometimes some portion present near wing margin); scutal vittae dark and shiny ( Fig. 62B).............. R. ( P.) diversipennis Becker
- Wing with normal venation; scutal vittae, when present, pruinose.............................................. 15
15 Legs including coxae yellowish to yellowish-brown......................................................... 16
- Legs including coxae dark............................................................................. 17
16 Wing entirely darkly infuscate; scutum with brown vittae beneath rows of acrostichal and dorsocentral setae............................................................................................. R. ( D.) leptidiformis Frey
- Wing with infuscation fading toward wing base ( Fig. 62D); scutum uniformly greyish pruinose........................................................................................................ R. ( P.) hilariformis Frey
17 Anepisternum shiny; scutum with 1–2 pairs of shiny vittae between rows of acrostichals and dorsocentral setae......................................................................................... R. ( P.) ursinella Melander
- Anepisternum pruinose; scutum with or without shiny vittae.................................................. 18
18 Coxae with stout, stiff setae............................................................................ 19
- Coxae with thin setae................................................................................. 21
19 Wing darkly infuscate............................................................. R. ( P.) omissinervis Becker
- Wing faintly infuscate................................................................................ 20
20 Hind tibia with ventral setae nearly subequal in length to width of tibia..................... R. ( P.) kjellmanii Holmgren
- Hind tibia with ventral setae at most half-length of tibia width..................................................................................................... R. ( P.) frigida Sinclair, Vajda, Saigusa & Shamshev sp. nov.
21 Scutum with pair of shiny vittae between rows of acrostichals and dorsocentral setae and broad shiny supra-alar vitta................................................... R. ( P.) septentrionalis Sinclair, Vajda, Saigusa & Shamshev sp. nov.
- Scutum entirely pruinescent, with slightly prominent brownish vittae along rows of acrostichals and dorsocentral setae... 22
22 Smaller, about 5 mm; darker, scutum almost uniformly dark brown, legs robust; halter brown....................................................................................................... R. ( D.) erinacioides Malloch
– Larger, 6–7 mm; more greyish, scutal vittae quite distinct, legs slender; halter pale yellow........ R. ( D.) nigrita Zetterstedt