Key to Recent genera of Osmylidae

Lahulus Navás, 1930 is unknown beyond the original description and is not included at this time. All extant genera can be identified in the key primarily using wing characteristics, although genitalic characteristics are also provided where relevant. While fossil taxa with complete wing preservation can be identified to subfamily level using this key, genera are not included at this time as many are known only from wing fragments where important diagnostic features are not observable.

1. Hind wing (HW) CuP as a single branch, sometimes dichotomously forked along wing margin (Figs 9, 29, 42); female sternite 8 reduced to small knob-like sclerite located immediately anterior to the lower margin of tergite 9, distant from sternite 7 (note: female genitalia unknown in Gumillinae).................................................................. 2.

- HW CuP greatly elongate and pectinately branched along wing margin (Figs 4, 16, 26, 53, 56, 59, 62); female sternite 8 located immediately posterior to sternite 7................................................................ 9.

2. Antennae extremely long, exceeding the length of wing; ocelli absent; wings with fewer than five branches on RP before pterostigma; numerous radial crossveins present, gradate series absent (Brazil) (Figs 8–9)........................................................................................................ GUMILLINAE: Gumilla Navás.

- Antennae short and rarely extending beyond half-length of wing, never longer than wing; ocelli typically conspicuous but sometimes greatly reduced; wings usually with at least five branches on RP before pterostigma (Figs 30, 41); radial crossveins variable in number, inner gradate series distinct (Fig. 29) or indistinct (Fig. 42).................................... 3.

3. RP crossveins relatively few in number aside from the gradate series, inner gradate series distinct and distant from crossveins in basal half of wing (Fig. 29)......................................................... PROTOSMYLINAE: 4.

- RP crossveins numerous aside from the gradate series, inner gradate series often close to, and sometimes obscured by, irregular crossveins in basal half of wing (Fig. 42)................................................. SPILOSMYLINAE: 7.

4. Forewing (FW) with distinctive series of crossveins along wing margin in the radial field in addition to regular gradate series (New World: Ecuador) (Fig. 36)........................................................ Paryphosmylus Krüger.

- FW without series of crossveins along wing margin in radial field (Old World) (Figs 29, 35)......................... 5.

5. FW RP stem short, such that RP1 originates distinctly proximal to fork of M; FW with crossveins between M and stem of RP absent (Oriental, Eastern Palaearctic) (Figs 34–35)................................................ Lysmus Navás.

- FW with stem of RP long, such that RP1 originates on RP at, or more typically beyond, fork of MA and MP; FW with one or more crossveins between M and stem of RP, before origin of MA.............................................. 6.

6. FW with costal area broad basally with basal subcostal veinlets radiating at divergent angles on Sc (Oriental Region) (Figs 27– 29)................................................................................. Gryposmylus Krüger.

- FW with costal area narrow basally with basal subcostal veinlets equidistant and sub-parallel to each other (Oriental Region) (Figs 31–32)........................................................................ Heterosmylus Krüger.

7. FW with regular series of 2–4 basal m-cu crossveins before MA-MP fork (South East Asia) (Figs 43–44).................................................................................................. Thaumatosmylus Krüger.

- FW with single m-cu crossvein before MA-MP fork (Fig. 46)................................................. 8.

8. Numerous extensive markings on forewing, typically with a fenestrate patch present at the outer gradate series; embossed bulla absent along hind margin of FW (Madagascar, South East Asia) (Figs 45–47)..................... Thyridosmylus Krüger.

- Forewing typically hyaline with markings much less extensive, embossed bulla usually present along hind margin of the FW in CuA region (sometimes absent) (Australasia, Madagascar, Africa, Oriental Region) (Figs 40–42)....... Spilosmylus Kolbe.

9. FW MA-MP fork in basal half of wing; few to many subcostal veinlets forked (rarely all simple) (Figs 4, 16); male with eversible scent glands between abdominal tergites 8 and 9....................................................... 10.

- FW MA-MP fork in the distal half of wing; subcostal veinlets all simple (rarely occasionally forked) (Figs 26, 53, 56); male abdominal tergites 8 and 9 fused into a single sclerite, lacking eversible scent glands............................... 16.

10. HW area between MA-MP usually distinctly expanded, MP often forking in distal third (sometimes absent), branches of MP bifurcate near wing margin (Fig. 16); wing frequently falcate; male genitalia with parameres absent; female genitalia with gonapophysis 9 enlarged located anterior to ventral portion of tergite 9, often ornately modified and lobed (southern hemisphere).............................................................................. KEMPYNINAE: 11.

- HW area between MA-MP only slightly expanded, MP never forking in distal third, HW MP pectinately branched near wing margin (Fig. 4); wing never falcate; male genitalia with parameres present as paired rod-like structures lateral to mediuncus; female genitalia with gonapophysis 9 as regular sclerite closely associated to gonocoxites 9 and posterior to ventral region of tergite 9, unmodified and sometimes difficult to differentiate from gonocoxites 9 (northern hemisphere)... OSMYLINAE: 13.

11. HW MA-MP fork relatively wide, crossveins between branches somewhat sinuous; large species (Australia, New Zealand and western South America) (Figs 13–16)........................................................ Kempynus Navás.

- HW MA-MP fork narrower, cells between branches sub-quadrate; small to medium sized species (Figs 10, 12)......... 12.

12. Wings distinctly falcate; small species (forewing length <15.0 mm) (New Zealand) (Fig. 12)............ Euosmylus Krüger.

- Wings scarcely falcate; medium sized species (forewing length>20.0 mm) (Australia) (Fig. 10)..... Australysmus Kimmins.

13. FW with very sparse RP crossveins basal to the two distinct gradate series (China) (Fig. 23)............. Sinosmylus Yang.

- FW RP crossveins dense basal to the one or two distinct gradate series (Figs 18–22)............................... 14.

14. Two distinct gradate series present; (Palaearctic) (Figs 18–21).................................... Osmylus Latreille.

- One distinct gradate series, or gradates absent (eastern Palaearctic) (Fig. 22)..................................... 15.

15. FW relatively large (31–32 mm long) without maculation and with uniformly pale-brownish veins; gonarcus with paired long dorsal processes (each longer than the height of the gonarcus), each terminated by paired acute denticles................................................................................................. Grandosmylus Makarkin.

- FW smaller (less than 30 mm long) with irregular mottled infuscation; veins with dark and pale sections; gonarcus dorsal process (when present) not as long and without terminal denticles (Fig. 22)......................... Parosmylus Needham.

16. FW basal branch RP1 distant to the wing base (nearer to middle third of the wing), more than six ra-rp crossveins before origin of the basal RP branch (Figs 6, 26) (Australia)............................................................. 17.

- FW basal RP1 branch diverging from RP closer to the wing base, fewer than four ra-rp crossveins before origin of branch RP1 (Figs 48–62)...................................................................... STENOSMYLINAE: 18.

17. FW with numerous sc-r crossveins (Australia) (Figs 24–26)...................... PORISMINAE: Porismus McLachlan.

- FW with a single basal sc-r crossvein (Australia) (Fig. 6)............ EIDOPORISMINAE: Eidoporismus Esben-Petersen.

18. FW MA-MP fork near wing margin and containing few branches (usually 2–4) (Australia) (Note: some individuals of Stenolysmus and Oedosmylus appear to have this condition as MP is fused with CuA; in these cases the fork of MP is represented as an atypical oblique crossvein located around midpoint of wing and CuA having an unusually large number of branches (Fig. 59)) (Figs 60–62)...................................................... Stenosmylus McLachlan.

- FW with distinct MA-MP fork at, or slightly beyond, midpoint of wing length; MA and MP fields both with numerous distinct branches (Figs 52, 56, 59)............................................................................ 19.

19. FW cubital space (bordered by CuA and CuP) curved sharply towards posterior wing margin around level of MA-MP fork (Figs 48, 50, 53).................................................................................... 20.

- FW cubital space straight along entire length, sometimes only slightly curved distally (Figs 56, 59)................... 22.

20. Wings extensively marked, dark brownish-black with contrasting white apical patches (Australia) (Fig. 48).................................................................................................... Euporismus Tillyard.

- Wings markings not so extensive, lacking contrasting white apical patches...................................... 21.

21. Female with FW veins MP, CuA and/or A1 partially incrassate; male with ectoprocts rounded, not lobed (Australia) (Figs 51– 53).................................................................................. Oedosmylus Krüger.

- Female with all FW veins of similar thickness, none incrassate; male with ectoprocts with distinct lobes or processes (South America) (Figs 49–50)............................................................... Isostenosmylus Krüger.

22. FW falcate; FW stem of RP relatively short, such that length of RP stem shorter than distance between first and second branches of RP (South America) (Figs 54–56)............................................. Phymatosmylus Adams.

- FW rounded, not falcate; FW stem of RP length approximately equal to the distance between branches RP1 and RP2 (Australia)............................................................................................... 23.

23. Body of living individual bright orange with dark legs; FW A1 and A2 with relatively few branches and with extensive endtwigging; FW A1 terminates in wing margin level with second branch of RP; female sternite 7 with narrow posterior margin; sternite 8 as broad plate; gonocoxites 9 with a ‘fringed’ row of stout, hooked setae (Australia) (Figs 57–59).................................................................................................. Stenolysmus Kimmins.

- Body of living individual mottled brown; FW A1 and A2 with numerous branches and with extensive end-twigging; FW A1 terminates in wing margin level with fourth-fifth branch of RP; female sternite 7 with large keeled process; sternite 8 as lobed process; gonocoxites 9 without a row of stout setae (Australia)................................... Carinosmylus New.