Key to males of Neurostigma

Neurostigma furcivenula and N. chaetocephalum are excluded from the key as their male genitalia remain unknown..

1. Forewing with areola postica fused with M; M vein concave with a V-shape before bifurcation (Fig. 23H–K) ..................................................................................................................................... 2

– Forewing with areola postica free, not fused with M; M vein concave with a U-shape before bifurcation (Figs 3A–B, 8A–B, 12A–B, 16A–B, 20A–B, 23A–G) .................................................. 4

2. Proximal half of forewing homogeneously pigmented (Fig. 23K) .............. N. enderleini New, 1980

– Proximal half of forewing not homogeneously pigmented, with some areas having lighter pigmentation and other areas having distinctly darker pigmentation (Fig. 23H–J) ......................... 3

3. Large irregular dark brown spots from base of pterostigma to CuP (Fig. 23I) or only from M+CuA to CuP (Fig. 23H); small dark brown spot at pterostigma base transverse veins pigmented along its entire length (Fig. 23H–I) ..................................................................... N. xanthopterum New, 1980

– Almost continuous spot from base of areola postica to CuP, with central discontinuity; no irregular spot between half of anal vein and wing margin strongly pigmented spot along M+Cu (Fig. 23J) ... ........................................................................... N. atlanticum Reategui, Rafael & Silva-Neto, 2022

4. Forewing completely hyaline (Fig. 23E–G) ..................................................................................... 5

– Forewing not hyaline (Figs 3A–B, 8A–B, 12A–B, 16A–B, 20A–B, 23A–D) ................................. 7

5. M with three primary branches and third branch unforked (Fig. 23E); phallosome not as below ..... ........................................................................................................................................................... 6

– M with three primary branches, M 3 forked into M 3a and M 3b (Fig. 23F); posterior process of aedeagus short and straight distally; endophallus with two groups of small spines separated by reticulated area (Fig. 24A) ........................................................................................................................................... .............. N. lienhardi González-Obando, Carrejo-Gironza, Mendivil-Nieto & García Aldrete, 2021

6. Areola postica narrow, with Cua 1 touching wing margin at a point parallel to the second bifurcation of M (Fig. 23E); distal process of aedeagal arch wide and short; endophallus with two sclerites with numerous small spines, directed antero-laterally (Fig. 24E) .............................................................. ..................... N. newi González-Obando, Carrejo-Gironza, Mendivil-Nieto & García Aldrete, 2021

– Areola postica wide, with Cua 1 touching wing margin at a parallel point after the first bifurcation of M vein (Fig. 23G); posterior process of edeagal arch long and narrow with slight indentation of outer margin; endophallus with sharp spines directed antero-mesally, with long spicules on outer margin and dense field of short spines and spicules latero-posteriorly (Fig. 24H) ......................................... .......................................................................................................................... N. roesleri New, 1980

7. M+Cu has with slight concavity before bifurcation that gives rise to Cu A and M (Fig. 8A–B) ....... 8

– M+Cu straight, without concave region (Figs 3A–B, 16A–B, 20A–B, 24A–D) ............................. 9

8. Posterior process of aedeagal arch long and wide, with slight indentation of external and internal margins; anterior margin of endophallus with U-shaped indentation, originating two areas similar to ‘angels’ wings, extremely membranous, ending posteriorly with six strongly sclerotized and acuminate projections (Fig. 9C) ...................................................................... N. angelicum sp. nov.

– Posterior process of aedeagal arch long, wide, with long indentation of external margin, and slight indentation of internal margin; endophallus with two distinctly sclerotized areas, with separate endophallic sclerites touching anteriorly, separated posteriorly by membranous area, each sclerite with denticulated posterior margin with numerous small acuminate projections coiled anteriorly, giving rise to spiral area (Fig. 13C) .................................................................... N. patriciae sp. nov.

9. Pterostigma with spot on distal half, M gently concave before first bifurcation (Fig. 23D); endophallus subquadrate with recess, originating two symmetrical regions composed of two lobes with numerous rows of vertical spines (Fig. 24G) ........................................................ N. paucivenosum New, 1980

– Pterostigma without spots or with spot only along crossveins; M vein gently concave with U-shaped before its bifurcation (Figs 3A–B, 16A–B, 20A–B, 23A–C) ......................................................... 10

10. R 2+3 four times as long as section Rs (Fig. 23B); endophallus region without sclerites or spines ..... ..........................................................................................................................................................11

– R 2+3 two times as long as section Rs (Fig. 24I); endophallus region with sclerites or spines ........ 12

11. M 3 unbifurcated; areola postica rounded distally (Fig. 23B); edeagal arch posterior process robust, rounded apically (Fig. 24C) ................................................................................................................ ............ N. mockfordi González-Obando, Carrejo-Gironza, Mendivil-Nieto & García Aldrete, 2021

– M 3 bifurcated into M 3a and M 3b; areola postica almost triangular distally (Fig. 23A); aedeagal arch distal process narrow, almost truncate apically (Fig. 24B) ................................................................. ........ N. valderramae González-Obando, Carrejo-Gironza, Mendivil-Nieto & García Aldrete, 2021

12. Aedeagal arch posterior process short and wide, apically U-shaped; endophallus with pair of golf club-shaped sclerites separated by membranes (Fig. 24I) ..................... N. dispositum Roesler, 1940

– Aedeagal arch posterior process robust and long; endophallus with sclerites sepated by membranes (Figs 4C, 17B, 21C, 24A–F) ........................................................................................................... 13

13. Endophallus with sclerites and spines V-shaped (Figs 4C, 24F) .................................................... 14

– Endophallus without sclerites and with anchor-shaped spines (Figs 17B, 21C, 24D) ................... 15

14. Areola postica wide, with Cua 1 touching wing margin at parallel point, after second bifurcation of M (Fig. 23C); endophallus with two distinctly long, sclerotized and acuminate sclerites directed antero-laterally, arising from dense field of small spines (Fig. 24F) .............. N. radiatum Mockford, 1991

– Areola postica narrower basally, with Cua 1 touching wing margin at point parallel between first and second bifurcation of M (Fig. 3A–B); endophallus with numerous V-shaped small spines, radula with two sclerites, these almost together in middle of endophallus, basally almost triangular and weakly sclerotized, posteriorly strongly sclerotized, with numerous acuminate projections, with two medially detached projections (Fig. 4C) .............................................................. N. alfonsoi sp. nov.

15. Endophallus with indentation in anterior region, laterally with rows of spines (Fig. 24D) ............... ............. N. thorntoni González-Obando, Carrejo-Gironza, Mendivil-Niero & García Aldrete, 2021

– Endophallus not as above (Figs 17B, 21C) .................................................................................... 16

16. Endophallus with slight central indentation, with field of spines close to posterolateral margins with numerous small spines on posterior edges, separated by large membranous area (Fig. 21C) ............ .......................................................................................................................... N. willkeniae sp. nov.

– Endophallus with median region deeply septate with V-shaped indentation, laterally membranous with seven distinct rows of spines, separated by membranous area (Fig. 17B) ................................. ........................................................................................................................... N. spinosum sp. nov.