KEY TO THE ADULT ATRICHOPOGON KIEFFER, 1906 WITH PIGMENTED WINGS OF THE NEOTROPICAL REGION

The males of A. (A.) nebulosus Macfie, 1939 and A. (A.) nubeculosus Macfie, 1949 and the females of A. (A.) ornatipennis Clastrier, 1987, A. (A.) pictipennis Clastrier, 1979 and A. (A.) delecollei Rossi, Marino & Spinelli, n. sp. are unknown. Since the females of different species are very similar, it is highly recommended to make the sex association.

1. Wing with extensive dark spots, covering all apical margin of wing (Figs 5D; 6C) ........................................ 2

— Wing with two dark spots, one over r-m and second in cell r 3 posterior to apex of R 3 (Figs 1E; 2C; 3D; 4C; 7D) .......................................................................................................................................................... 4

2. Distal 1/3 of wing dark with two elliptic pale spots, one subapically in r 3 and another extending from apical portion of m 1 to m 2; males with gonostylus gradually tapering and curved, with pointed apex ....................... ................................................................................................................... A. (A.) cavus Felippe-Bauer, 2012

— Distal 1/3 of wing entirely dark (Figs 5D; 6C) ............................................................................................ 3

3. Hind leg paler than fore and midlegs (Fig. 5E); males with gonostylus slender, tapering from base, apex single (Figs 5F; 8C) ............................................................................ A. (A.) soriai Rossi, Marino & Spinelli, n. sp.

— Legs with similar coloration; males with gonostylus thick with two pointed apical prongs .............................. ................................................................................................................ A. (A.) maculipennis Clastrier, 1968

4. Males .......................................................................................................................................................... 5

— Females ..................................................................................................................................................... 18

5. Gonostylus tapering flattened and curved, apex spatulate or with flange (Figs 1G, 8A) ............................... 6

— Gonostylus double, forked or single, pointed at apex (Figs 3G; 5F; 7G; 8B; 8C; 8D) ................................. 7

6. Antenna without sexual secondary dimorphism (Fig. 1A); scutum without lateral suture (Fig. 1D) ................ ............................................................................................. A. (A.) tricuspis Rossi, Marino & Spinelli, n. sp.

— Antenna with plume setae (Fig. 3A); scutum with lateral suture (Fig. 7E) ...................................................... .............................................................................................................. A. (A.) janseni Pessoa & Farias, 2021

7. Gonostylus double or forked (Figs 3G; 8B) ................................................................................................. 8

— Gonostylus single, not forked (Figs 5F; 7G; 8C; 8D) ................................................................................ 15

8. Gonostylus double, articulated at base ......................................................................................................... 9

— Gonostylus forked, not articulated at base (Figs 3G; 8B) ........................................................................... 10

9. Posterior margin of tergite 9 rounded, not surpassing apex of gonocoxite; sternite 9 with lateral group of scattered setae .................................................................................... A. (A.) casali Cavalieri & Chiossone, 1973

— Posterior margin of tergite 9 elongated as a setose finger-like process, greatly surpassing apex of gonocoxite; sternite 9 with transverse row of setae ...................................................... A. (A.) dactilus Felippe-Bauer, 2012

10. Gonostylus forked near its base ................................................................................................................. 11

— Gonostylus forked near midlength or close to the apex .............................................................................. 12

11. Inner portion of gonostylus slender, strongly curved .................................. A. (A.) pictipennis Clastrier, 1979

— Inner portion of gonostylus slender, nearly straight ........................... A. (A.) shawadawa Felippe-Bauer, 2018

12. Gonostylus forked close to the apex, basal half swollen and inner prong sclerotized ....................................... .............................................................................................. A. (A.) sergioluzi Farias, Santos & Pessoa, 2021

— Gonostylus forked near midlength (Figs 3G; 8B) ...................................................................................... 13

13. Trochanter of hind leg bearing black spines (Fig. 3E) .. A. (A.) trochantispina Rossi, Marino & Spinelli, n. sp.

— Trochanter of hind leg without black spines .............................................................................................. 14

14. Inner portion of gonostylus elongate, curved apically, longer than outer portion ............................................ .................................................................................................................. A. (A.) nukini Felippe-Bauer, 2018

— Outer portion of gonostylus 4 × longer than inner portion ............................................................................... ................................................................................... A. (A.) riopardensis Farias, Pessoa & Paulino-Rosa, 2021

15. Posterior margin of tergite 9 with 1 or 2 small median lobes ..................................................................... 16

— Posterior margin of tergite 9 rounded, without lobes.................................................................................. 17

16. Posterior margin of tergite 9 bilobated ............................................. A. (A.) bicuspis Borkent & Picado, 2004

— Posterior margin of tergite 9 with a small median lobe ................... A. (A.) clastrieri Spinelli & Marino, 2007

17. Gonostylus thick; gonocoxal apodeme stout, directed laterally ................. A. (A.) ornatipennis Clastrier, 1987

— Gonostylus slender tapering from base; gonocoxal apodeme slender, directed anteriorly (Figs 7F; 8D) ........... ............................................................................................ A. (A.) delecollei Rossi, Marino & Spinelli, n. sp.

18. Abdominal tergites 1-6 or 1-3 and 5-6 with dark lateral patches (Fig. 5D) ................................................ 19

— Abdominal tergites 1-6 without dark lateral patches (Figs 2D; 6D) ........................................................... 27

19. Abdominal tergites 1-6 with dark lateral patches ....................................................................................... 20

— Abdominal tergites 1-3 and 5-6 with dark lateral patches, tergite 4 without or with a smaller patch (Fig. 5D) .................................................................................................................................................................. 21

20. Flagellomeres 9-13 paler than flagellomeres 1-8; mandible without teeth ....................................................... .............................................................................................................. A. (A.) janseni Pessoa & Farias, 2021

— Flagellomeres uniformly brown; mandible with 20 teeth .............. A. (A.) casali Cavalieri & Chiossone, 1973

21. Trochanter of hind leg with black spines (Fig. 3E) ....... A. (A.) trochantispina Rossi, Marino & Spinelli, n. sp.

— Trochanter of hind leg without black spines .............................................................................................. 22

22. Palpus with segments 4 and 5 partially fused .......................................... A. (A.) dactilus Felippe-Bauer, 2012

— Palpus with segments 4 and 5 separated .................................................................................................... 23

23. Spermatheca large and elliptical, about as broad as long, with elongate and stout neck ................................... .............................................................................................. A. (A.) sergioluzi Farias, Santos & Pessoa, 2021

— Spermatheca ovoid, longer than broad, with short neck ............................................................................ 24

24. Mandible poorly developed, without teeth ................................................................................................ 25

— Mandible well developed, with teeth ......................................................................................................... 26

25. Wing length longer than 1.13 mm .................................................... A. (A.) shawadawa Felippe-Bauer, 2018

— Wing length shorter than 1.10 mm .......................................................... A. (A.) nukini Felippe-Bauer, 2018

26. Wing length longer than 1.14 mm; mandible with 21 teeth ............. A. (A.) bicuspis Borkent & Picado, 2004

— Wing length shorter than 0.90 mm; mandible with 24 teeth .......................................................................... ................................................................................. A. (A.) riopardensis Farias, Pessoa & Paulino-Rosa, 2021

27. Posterior margin of scutum with pair of bunches of short setae, each on stout rounded base (Fig. 1D) ....... 28

— Posterior margin of scutum without bunches of short setae ....................................................................... 29

28. Spermatheca lightly sclerotized .................................................................... A. (A.) nubeculosus Macfie, 1949

— Spermatheca heavily sclerotized, scutum without lateral suture (Fig. 2E, 9A) ................................................. ............................................................................................. A. (A.) tricuspis Rossi, Marino & Spinelli, n. sp.

29. Flagellomeres 9-13 darker than flagellomeres 1-8 ............................................ A. (A.) nebulosus Macfie, 1939

— Flagellomeres 9-13 paler than flagellomeres 1-8 .............................. A. (A.) clastrieri Spinelli & Marino, 2007