Tachydromia, Meigen, 1803

Shamshev, Igor V. & Grootaert, Patrick, 2024, Revision of the described Nearctic species of the genus Tachydromia Meigen (Diptera: Hybotidae), Zootaxa 5403 (2), pp. 151-196 : 191-193

Key to described species of Tachydromia from the Nearctic

1 Male ............................................................................................... 2

- Female............................................................................................ 18

2 Palpus bicoloured (black to brown apically and pale yellow on basal part), lacking subapical seta (e.g., Fig. 2B ). Wing with vein R 2+3 strongly turned towards costa at apex (e.g., Fig. 2C )...................................................... 3

- Palpus unicoloured (entirely black to brown or yellow to whitish) (e.g., Fig. 1 ); with subapical, usually black, seta. Wing with vein R 2+3 usually gradually arched apically (except T. enecator )................................................. 7

3 Palpus with deep lateral excision on black apical portion (bilobate) (e.g., Fig. 2B, C )................................ 4

- Palpus not divided into two lobes apically (e.g., Fig. 15B )..................................................... 5

4 Palpus with pale yellow portion nearly as long as black portion. Fore and mid legs extensively yellow (including fore coxae) ( Fig. 2A ). Mid femur and tibia unmodified................................................ T. bimaculata (Loew)

- Palpus with pale yellow portion at least 1.5 times longer than black portion ( Fig. 17A ). Legs almost uniformly brown. Mid femur thickened, with broad basal excavation armed with row of about 8 long, strong anteroventral setae; mid tibia with subapical excavation forming large, thumb-like, posteromarginal projection ( Fig. 17A ).............. T. tacoma Melander

5 Head and thorax with pale setae. Legs almost uniformly blackish brown, only knees yellowish ( Fig. 15A ); mid tibia with short subapical setae...................................................................... T. punctifera (Becker)

- Head and thorax with black setae. Legs partly yellowish, at least fore coxa always yellow; mid tibia with 2 long, fine, closely set subapical setae posteriorly........................................................................... 6

6 Proepisternum shiny. Occiput densely greyish pruinose on about upper half only. Palpus usually more or less broadened towards apex, brown to blackish brown on apical 1/4 to 1/2 ( Fig. 9A )................................. T. incompleta (Becker)

- Proepisternum tomentose (except narrow upper part). Occiput mostly densely greyish pruinose, shiny behind mouth-opening. Palpus usually somewhat narrowed towards apex; mostly pale yellow, narrowly brownish at apex ( Fig. 4A )................................................................................................. T. chelana Melander

7 Wings with two brownish bands, either entirely separated or connected at least in cell r 1 (e.g., Figs 1 , 18A ).............. 8

- Wings with different pattern (not banded) or nearly hyaline (e.g., Fig. 10A )...................................... 15

8 Wings with brownish bands entirely separated (e.g., Fig. 1 ).................................................... 9

- Wings with brownish bands connected in cell r 1 or in cells r 1 and r 2+3 (e.g., Fig. 18A )............................... 14

9 Fore tibia uniformly yellow or dark...................................................................... 10

- Fore tibia yellow, with 1 or 2 blackish to brown spots on apical half anteriorly.................................... 11

10 Antenna uniformly brown to blackish brown. Palpus clothed in minute dark setulae. Legs almost uniformly blackish brown, only knees and basitarsi paler ( Fig. 6A ). Wing with vein R 2+3 usually emitting short subapical appendix. Halter brownish...................................................................................... T. enecator Melander

- Antenna with scape and pedicel yellow. Palpus clothed in numerous adpressed silvery setae. Legs extensively yellow. Wing with vein R 2+3 lacking subapical appendix. Halter with pale yellow knob ( Fig. 1 )..................... T. aemula (Loew)

11 Fore tibia with 1 spot (e.g., Fig. 13A ).................................................................... 12

- Fore tibia with 2 spots (e.g., Fig. 8 )...................................................................... 13

12 Proepisternum entirely densely tomentose. Fore tibia with rounded elongate oval subapical brownish spot anteriorly ( Fig. 13A ). Wings shortened.................................................................... T. phengites Melander

- Proepisternum densely tomentose only on about lower half. Fore tibia abruptly black on about apical 1/3 anteriorly. Wings normally developed................................................................. T. diversipes Melander

13 Proepisternum tomentose.................................................................. T. harti Malloch

- Proepisternum shiny............................................................... T. pseliophora Melander

14 Wings with brownish bands connected on cell r 1. Proepisternum shiny. Fore legs covered with long hair-like setae.......................................................................................... T. schwarzii Coquillett

- Wings with brownish bands connected across cells r 1 and r 2+3 ( Fig. 18A ). Proepisternum tomentose. Fore legs with simple, short setae............................................................................ T. varipennis Coquillett

15 Wings almost hyaline, with faint brownish infuscation along longitudinal veins ( Fig. 7A ). Halter with pale yellow knob. Mesonotum with 1 notopleural seta. Male: right epandrial lamella with small mid-ventral projection bearing tuft of long flattened setae ( Fig. 7C )................................................................ T. fuscinervis (Frey) [The Palaearctic T. microceroides Chvála would key here. This species differs from T. fuscinervis only by more extensively shiny occiput (only central area of occiput just above neck and below neck towards mouth-opening thinly grey pruinose).]

- Wings with faint, brownish, indistinctly bordered infuscation including cells r 1 (except narrow basal portion) and r 2+3 (e.g., Fig. 10A ). Halter with brownish knob. Mesonotum usually with 2 notopleural setae (anterior seta shorter). Right epandrial lamella without flattened setae ventrally......................................................................... 16 [ T. preapicalis ( Collin, 1941) and T. mucronata ( Collin, 1941) known only from the Russian Far East would key here. Both species can be readily distinguished from described Nearctic members of this complex primarily by yellow knob of halteres.]

16 Proepisternum shiny. Fore tarsomeres 1–3 yellow, tarsomeres 4–5 brown ( Fig. 10A )............. T. maculipennis Walker

- Proepisternum tomentose. Fore tarsus brownish............................................................ 17

17 Fore femur yellow at extreme apex and on basal 1/4 to 1/3................................. T. magadanica Shamshev

- Legs almost uniformly brown, only knees yellowish........................................ T. monacha Melander [The Palaearctic T. halterata (Collin) would key here. This species is very similar to T. magadanica differing by distinct excavation near base of male mid femur.]

18 Palpus without black subapical seta. Wing with vein R 2+3 strongly turned towards costa at apex....................... 19

- Palpus with black subapical seta. Wing with vein R 2+3 usually gradually arched apically (except T. enecator )............ 23

19 Palpus black. Vein R 2+3 sinuous.......................................................... T. tacoma Melander

- Palpus whitish. Vein R 2+3 straight........................................................................ 20

20 Head and thorax with pale setae (sometimes stronger setae yellowish).......................................... 21

- Head and thorax with black setae........................................................................ 22

21 Fore and mid legs extensively yellow (including fore coxae). Mid femur with rows of black, spine-like anteroventral and posteroventral setae on apical half....................................................... T. bimaculata (Loew)

- Legs almost uniformly blackish brown, only knees yellowish. Mid femur with fine anteroventral and posteroventral setae..................................................................................... T. punctifera (Becker)

22 Proepisternum shiny. Occiput densely greyish pruinose on about upper half only................. T. incompleta (Becker)

- Proepisternum tomentose (except narrow upper part). Occiput mostly densely greyish pruinose, shiny behind mouth-opening................................................................................... T. chelana Melander

23 Wings with two brownish bands, either entirely separated or connected at least in cell r1............................ 24

- Wings with different pattern (not banded) or nearly hyaline................................................... 31

24 Wings with entirely separated brownish bands............................................................. 25

- Wings with brownish bands connected in cell r 1 or in cells r 1 and r 2+3........................................... 30

25 Halter brown. Legs almost uniformly blackish brown, only knees and basitarsi paler. Vein R 2+3 usually emitting short subapical appendix........................................................................... T. enecator Melander

- Halter yellow. Legs extensively yellow. Vein R 2+3 lacking subapical appendix..................................... 26

26 Fore femur with rows of black, spinule-like anteroventral and posteroventral setae. Palpus clothed in numerous adpressed silvery setae............................................................................. T. aemula Loew

- Fore femur with pale, fine setae ventrally. Palpus with scattered dark setulae..................................... 27

27 Proepisternum entirely shiny........................................................ T. pseliophora Melander

- Proepisternum tomentose at least on lower half............................................................. 28

28 Proepisternum densely tomentose only on lower half, subshiny on upper half. Mid tibia brown...... T. diversipes Melander

- Proepisternum entirely densely tomentose. Mid tibia yellow.................................................. 29

29 Occiput entirely shiny. Wings shortened, somewhat shorter than abdomen...................... T. phengites Melander

- Occiput on upper part with large spot of greyish pruinosity reaching eye margins. Wings normally developed................................................................................................... T. harti Malloch

30 Wings with brownish bands connected on cell r 1. Proepisternum shiny......................... T. schwarzii Coquillett

- Wings with brownish bands connected on cells r 1 and r 2+3. Proepisternum tomentose............. T. varipennis Coquillett

31 Wings almost hyaline, with faint brownish infuscation along longitudinal veins. Halter with pale yellow knob. Mesonotum with 1 notopleural seta..................................................................... T. fuscinervis (Frey)

- Wings with faint, brownish, diffuse infuscation including cells r 1 (except narrow basal portion) and r 2+3. Halter with brownish knob. Mesonotum usually with 2 notopleural setae (anterior seta shorter)........................................ 32

32 Proepisternum shiny. [Additional character: Fore femur distinctly dark brown ringed, usually yellow on about basal and apical 1/4]............................................................................. T. maculipennis Walker

- Proepisternum tomentose.............................................................................. 33

33 Legs with yellow pattern including at least fore coxae and trochanters and extreme apex and basal 1/4 to 1/3 of fore femora................................................................................. T. magadanica Shamshev

- Legs almost uniformly brown, only knees yellowish........................................ T. monacha Melander

Figures

FIGURE 1. Tachydromia aemula (Loew). Male habitus, lateral view (Canada, Quebec; CNC).

FIGURE 2. Tachydromia bimaculata (Loew) (Canada, British Columbia; CNC). A. Male habitus, lateral view. B. Male head, anterior view. C. Male palpus, dorsal view. D. Female habitus, lateral view. E. Female head, anterior view. Abbreviation: plp—palpus.

FIGURE 4. Tachydromia chelana Melander, male (Canada, Northwest Territories; CNC). A. Habitus, lateral view. B. Hypopygium,dorsal view.C. Right surstylus, lateral view.D. Left epandrial lamella andleft surstylus, lateral view.Abbreviations: cerc—cercus; lft sur—left surstylus; rt sur—right surstylus. B–D: scale bar is 0.1 mm.

FIGURE 6. Tachydromia enecator Melander, male (Canada, Alberta; CNC). A. Habitus, lateral view. B. Hypopygium, dorsal view. C. Right surstylus, lateral view. D. Left epandrial lamella and left surstylus, lateral view.Abbreviations: cerc—cercus; lft sur—left surstylus; rt sur—right surstylus. B–D: scale bar is 0.1 mm.

FIGURE 7. Tachydromia fuscinervis (Frey), male (USA, Alaska; CNC). A. Habitus, lateral view. B. Hypopygium, dorsal view. C. Right epandrial lamella, right surstylus and right cercus, lateral view. D. Left epandrial lamella and left surstylus, lateral view. Abbreviations: cerc—cercus; lft sur—left surstylus; rt cerc—right cercus; rt sur—right surstylus. B–D: scale bar is 0.1 mm.

FIGURE 8. Tachydromia harti Malloch, male habitus, lateral view (Canada, Manitoba; CNC).

FIGURE 9. Tachydromia incompleta (Becker), habitus, lateral view (Sweden, Abisco; CNC). A. Male. B. Female.

FIGURE 10. Tachydromia maculipennis Walker, male (Canada, Ontario; CNC). A. Habitus, lateral view. B. Hypopygium, dorsal view. C. Right epandrial lamella and right surstylus, lateral view. D. Left epandrial lamella and left surstylus, lateral view. Abbreviations: cerc—cercus; epand—epandrium; hypd—hypandrium; lft sur—left surstylus; rt sur—right surstylus. B–D: scale bar is 0.1 mm.

FIGURE 13. Tachydromia phengites Melander (Canada, Ontario; CNC). A–D. Male. A. Habitus, lateral view. B. Hypopygium, dorsal view. C. Right epandrial lamella and right surstylus, lateral view. D. Left epandrial lamella and left surstylus, lateral view. E. Female habitus, lateral view.Abbreviations: cerc—cercus; lft sur—left surstylus; rt sur—right surstylus. C–D: scale bar is 0.1 mm.

FIGURE 15. Tachydromia punctifera (Becker) (Canada, Northwest Territories; CNC). A–E. Male. A. Habitus, lateral view. B. Head, anterior view. C. Hypopygium, dorsal view. D. Right surstylus, lateral view. E. Left epandrial lamella and left surstylus, lateral view. F. Female head, anterior view. Abbreviations: cerc—cercus; lft sur—left surstylus; rt sur—right surstylus. C–E: scale bar is 0.1 mm.

FIGURE 17. Tachydromia tacoma Melander (USA, Washington;USNM).A–D. Male. A. Habitus,lateral view.B. Hypopygium, dorsal view. C. Right surstylus, lateral view. D. Left epandrial lamella and left surstylus, lateral view. E. Female head, lateral view. Abbreviations: cerc—cercus; lft sur—left surstylus; rt sur—right surstylus. B–D: scale bar is 0.1 mm.

FIGURE 18. Tachydromia varipennis Coquillett, male (USA, Virginia; CNC). A. Habitus, lateral view. B. Hypopygium, dorsal view. C. Right surstylus, lateral view. D. Left epandrial lamella and left surstylus, lateral view.Abbreviations: cerc—cercus; lft sur—left surstylus; rt sur—right surstylus. B–D: scale bar is 0.1 mm.