Key to Middle America Stenamma

The following worker key is based on Branstetter, M.G. 2013. Revision of the Middle American clade of the ant genus Stenamma Westwood (Hymenoptera, Formicidae, Myrmicinae). ZooKeys 295, 1–277. doi:10.3897/zookeys.295.4905

1

 * Anterior constriction of gaster, along with basal striae, distinctly elongate (Couplet Figure 1.A,B) . . . . . 2


 * Anterior constriction of gaster and basal striae not elongate (Couplet Figure 1.C) . . . . . 3

2
return to couplet #1
 * Surface sculpture almost entirely smooth and shiny (Couplet Figure 2.A); anterior clypeal margin in full-face view with a shallow median emargination (Couplet Figure 2.A) (Honduras) . . . . . Stenamma atribellum


 * Face and much of mesosoma with conspicuous carinulae (Couplet Figure 2.B); median lobe of clypeus projecting over anterior clypeal margin, forming a well-defined median apex (Couplet Figure 2.B) (Guatemala) . . . . . Stenamma callipygium

3
return to couplet #1
 * Anterior clypeal margin in full-face view forming three well-defined teeth (visible even if mandibles closed), with middle tooth formed by median lobe, which projects over true clypeal margin (Couplet Figure 3.A); frontal lobes markedly expanded outward, completely obscuring torular lobes in full-face view (Couplet Figure 3.A) (FLD 0.24–0.26, FLI 36–39); head and mesosoma densely sculptured with rugoreticulae and punctae; propodeal spines well-developed (Couplet Figure 3.B) (SSL 0.16–0.19, PSI 1.8–2.2) (Honduras) . . . . . Stenamma cusuco


 * Anterior clypeal margin in full-face view variable, not as above (Couplet Figure 11.A-I); frontal lobes, body sculpture, and propodeal spines variable . . . . . 4

4
return to couplet #3
 * Face and promesonotal dorsum foveate to coarsely rugoreticulate (Couplet Figure 4. A, B); pilosity on gastral tergites long, dense, and mostly suberect (Couplet Figure 4. C); eyes relatively small (EL 0.09–0.13, REL 10–16), with 5–8 ommatidia at greatest diameter; 4-segmented antennal club indistinct; larger species (HL 0.87–1.20, HW 0.78–1.15, ML 1.15–1.62) . . . . . 5


 * Sculpture variable, but not distinctly foveate; other characters variable, not as above . . . . . 6

5
return to couplet #4
 * Anterior clypeal margin forming four relatively sharp teeth (middle teeth only visible if mandibles open) (Couplet Figure 5. A); propodeal spines reduced to sharp angles or small tubercles (Couplet Figure 5. D) (SSL 0.12–0.16, PSI 1.0–1.3); somewhat smaller species (HL 0.87–1.03, HW 0.78–0.92, ML 1.15–1.38) (eastern Honduras to Panama) . . . . . Stenamma zelum


 * Anterior clypeal margin with a median emargination that has four well-defined to completely effaced blunt teeth (Couplet Figure 5. B, C); propodeal spines usually present, ranging from short tubercles to long robust spines (Couplet Figure 5. E-G) (SSL 0.15–0.37, PSI 1.3–2.9); somewhat larger species (HL 0.90–1.20, HW 0.77–1.15, ML 1.15–1.62) (Mexico to western Honduras) . . . . . Stenamma brujita

6
return to couplet #4
 * Lateral apex of hypostomal bridge projecting ventrally as a subquadrate (Couplet Figure 6. A, B) to broadly rounded (Couplet Figure 6. C) lobe, visible behind base of mandible in profile view . . . . . 7


 * Lateral margin of hypostomal bridge tapering to a narrow point, not visible in profile view (Couplet Figure 6. D-F) . . . . . 11

7
return to couplet #6
 * Propodeal spines long and slender (SSL 0.17–0.22, PSI 1.9–2.2) (Couplet Figure 7. A); face with a dense fan of carinulae extending out from frontal lobes toward posterior and lateral margins of head (Couplet Figure 7. B); postpetiole appearing somewhat anteroposteriorly compressed (Couplet Figure 7. A) (southern Mexico) . . . . . Stenamma leptospinum (part)


 * Propodeal spines tuberculate or short; face sculpture and petiole variable, not as above . . . . . 8

8
return to couplet #7
 * Pronotum conspicuously punctate, with longitudinal rugulae faintly present among punctae on dorsum (Couplet Figure 8. A, B); suberect setae on gastral tergites very stout, somewhat sparse, short (Couplet Figure 8. C); propodeal spines present, short (SSL 0.16–0.19, PSI 1.4–1.6) (southern Mexico) . . . . . Stenamma longinoi


 * Lacking one or more of the above character states . . . . . 9

9
return to couplet #8
 * Petiole and postpetiole more slender, with postpetiole in profile appearing particularly small and elongate (Couplet Figure 9. A) (PPH/PH 0.74–0.84, PW/PPW 0.76–0.89); pronotum usually mostly smooth and shiny, with only some vestigial rugulae (Couplet Figure 9. A); smaller species (HL 0.72–0.83, HW 0.63–0.75, ML 0.89–1.08) (Honduras to Nicaragua) . . . . . Stenamma muralla


 * Waist segments more robust, with postpetiole in profile sometimes bulging and usually more circular (Couplet Figure 9. B-D) (PPH/PH ≥ 0.79, PW/PPW ≥ 0.87); pronotum sculpture variable, but usually more dense; larger species (HL ≥ 0.81, HW ≥ 0.70, ML ≥ 1.05) (Mexico to Nicaragua) . . . . . 10

10
return to couplet #9
 * Eye usually smaller (EL 0.10–0.16), with 5–8 ommatidia at greatest diameter; body color usually lighter, dark red-brown to brown, but sometimes orange-brown or yellow-brown (Couplet Figure 9. B, C) (Mexico to Nicaragua) . . . . . Stenamma manni (part)


 * Eye usually larger (EL 0.14–0.19), with 8–11 ommatidia at greatest diameter; body color mostly black (Couplet Figure 9. D) (southern Mexico to Nicaragua) . . . . . Stenamma megamanni

11
return to couplet #6
 * Basal margin of mandible straight to slightly sinuous, without a distinct basal notch or depression; anterior clypeal margin entire, or with a rounded median emargination, or with a deep median excision (rarely with mandible completely straight and anterior clypeal margin with 2 blunt teeth) . . . . . 12


 * Basal margin of mandible sinuous, with a shallow to deep basal depression or notch, but without a basal tooth; anterior clypeal margin undulating, forming 2–4 variably developed teeth (sometimes teeth very reduced, so clypeal margin is nearly flat) . . . . . 30


 * Basal margin of mandible sinuous, with a distinct basal depression or notch, and an accompanying small tooth; anterior clypeal margin usually undulating, forming 2–4 variably developed teeth . . . . . 41

12
return to couplet #11
 * Propodeal spines absent; petiole and postpetiole almost completely smooth and shiny, with only faint vestigial punctae sometimes present (Couplet Figure 20. A-D); postpetiole in profile bulging, globular, appearing more voluminous than petiolar node (Couplet Figure 20. A-D) . . . . . 13 (expolitum group)


 * Propodeal spines present or absent; petiole and postpetiole not as above, either with more conspicuous sculpturing, or with the postpetiole not distinctly larger than petiolar node . . . . . 15

13
return to couplet #12
 * Face almost completely smooth and shiny, with only some vestigial carinulae near frontal lobes and anterolateral margins of head (Couplet Figure 13. A); carinulae around frontal lobes extending to about midpoint of head or less; dorsum of promesonotum smooth and shiny (Nicaragua to Costa Rica) . . . . . Stenamma expolitum


 * Face with more extensive sculpture, consisting of a fan of carinulae that extend from the area around antennal insertions to at least midpoint of head, but sometimes reaching to posterior margin (Couplet Figure 13. B-D); dorsum of promesonotum smooth and shiny, or with variably developed transverse furrows or striae (Costa Rica to Ecuador) . . . . . 14

14
return to couplet #13
 * Dorsal and declivitous faces of propodeum in profile flat, and forming a blunt 90° angle (Couplet Figure 12. D); dorsum of promesonotum with distinctive transverse furrows, sometimes reticulate posteriad (Couplet Figure 14. C) (Costa Rica) . . . . . Stenamma expolitico


 * Propodeum in profile more rounded, with transition between dorsal and declivitous faces less abrupt (Couplet Figure 12. B, C); dorsum of promesonotum either smooth and shiny, or with few to many transverse striae (Couplet Figure 14. B, C) (Costa Rica to Ecuador) . . . . . Stenamma alas

15
return to couplet #12
 * Face mostly smooth and shiny, except for scattered piligerous punctae and at most a few carinulae, rugulae, and/or punctae around frontal lobes and anterolateral margins of head (Couplet Figure 15. A, B) . . . . . 16


 * Face sculpture more extensive, usually completely sculptured; type of sculpture variable (Couplet Figure 15. C) . . . . . 21

16
return to couplet #15
 * Dorsum of promesonotum mostly smooth and shiny, except for scattered piligerous punctae, and at most a few longitudinal rugulae (Couplet Figure 16. A, B) . . . . . 17


 * Dorsum of promesonotum with more extensive sculpturing, either reticulately costate or rugoreticulate (Couplet Figure 16. C) . . . . . 19

17
return to couplet #16
 * Mesosoma compact, with promesonotum somewhat bulging (Couplet Figure 17. A); propodeal spines present as short robust triangles (Couplet Figure 17. A) (SSL 0.09–0.14, PSI 1.7–2.5); petiolar node robust, relatively tall (PH/PL 0.66–0.80), and distinctly angled posteriad (Couplet Figure 17. A); scape and metafemur relatively short (SI 80–85, MFI 101–113) (southern Mexico to Honduras) . . . . . Stenamma llama


 * Lacking one or more of the above character states (Couplet Figure 17. B-D) . . . . . 18

18
return to couplet #17
 * Median lobe of clypeus bicarinate, projecting, and with area between carinae distinctly depressed (Couplet Figure 18. A); promesonotum in profile asymmetrical, with anterior slope long and gently curving, dorsum nearly flat, and posterior slope short and forming a sharp transition with dorsum (Couplet Figure 17. B); propodeal spines absent (SSL 0.06–0.07, PSI 1.0–1.3) (northern Mexico) . . . . . Stenamma tiburon


 * Median lobe of clypeus smooth and with a simple median emargination (Couplet Figure 18. B); promesonotum in profile usually asymmetrical (Couplet Figure 17. C), with posterior slope distinctly longer than anterior slope, but sometimes promesonotum more evenly domed (Couplet Figure 17. D); propodeal spines tuberculate to short (SSL 0.06–0.10, PSI 1.1–1.7) (Mexico to Honduras) . . . . . Stenamma pelophilum

19
return to couplet #16
 * Promesonotum in profile distinctly asymmetrical, with anterior slope long and gently curving, dorsum nearly flat and at a slight downward angle, and posterior slope short and forming a sharp transition with dorsum (Couplet Figure 19. A, B); postpetiolar node in profile with a longitudinal dorsal lobe that projects posteriorly over postpetiole (Couplet Figure 19. A, B) (Mexico) . . . . . Stenamma lobinodus


 * Promesonotum in profile low domed and roughly symmetrical (Couplet Figure 19. C, D); postpetiole in profile more circular and without a distinct dorsal lobe projecting posteriorly (Couplet Figure 19. B, C) . . . . . 20

20
return to couplet #19
 * Propodeal spines present, long (Couplet Figure 19. C) (SSL 0.28–0.34, PSI 3.0–3.7); frontal lobes expanded dorsolaterally, usually completely covering torular lobes in full-face view (Couplet Figure 20. A) (FLD 0.25–0.29, FLI 35–38); eye smaller (EL 0.11–0.15, REL 16–20) (southern Mexico to Nicaragua) . . . . . Stenamma diversum


 * Propodeal spines reduced to sharp right angles, or small upward projecting tubercles (Couplet Figure 19. D) (SSL 0.14–0.18, PSI 1.4–1.9); frontal lobes narrower, with torular lobes partly visible in full-face view (Couplet Figure 20. B, C) (FLD 0.22-0.27, FLI 33-36); eye larger and somewhat bulging (EL 0.15-0.18, REL 23–24) (Nicaragua to Panama) . . . . . Stenamma tico (part)

21
return to couplet #15
 * Propodeal spines absent, with the dorsal and declivitous faces of the propodeum forming a relatively shallow, blunt angle in profile view (Couplet Figure 21. A, B) (SSL 0.08–0.11, PSI 0.8–1.1); eyes large (EL ≥ 0.15, REL ≥ 18) . . . . . 22


 * Propodeal spines varying from tuberculate to long, or with the dorsal and declivitous faces of the propodeum forming a sharp, steep angle (Couplet Figure 21. C-E) (SSL ≥ 0.07, PSI ≥ 1.0); eyes variable . . . . . 23

22
return to couplet #21
 * Head and mesosoma strongly sculptured (Couplet Figure 21. A), (Couplet Figure 22. A, B); face mostly rugoreticulate or carinate; scape relatively shorter (SI 84–101); eye relatively smaller (REL 18–22); larger, more robust species (HL 0.90–1.19, HW 0.81–1.04, ML 1.25–1.62) (Mexico to Ecuador) . . . . . Stenamma felixi


 * Head and mesosoma more faintly sculptured (Couplet Figure 21. B), (Couplet Figure 22. C, D); face with variable amount of carinulae, rugulae, and punctae; scape relatively longer (SI 107–121); smaller, usually somewhat gracile species (HL 0.79–0.88, HW 0.65–0.73, ML 1.04–1.16) (Nicaragua to Ecuador) . . . . . Stenamma schmidti (part)

23
return to couplet #21
 * Facial sculpture light, largely effaced, usually not extending all the way to posterior margin of head (Couplet Figure 23. A); mesosoma mostly reticulately costate (Couplet Figure 23. B); propodeal spines reduced to sharp right angles, or small upward projecting tubercles (Couplet Figure 23. B) (PSL 0.14–0.18, PSI 1.4–1.9); eye large, somewhat bulging (EL 0.15-0.18, REL 23–24) (Nicaragua to Panama) . . . . . Stenamma tico (part)


 * Lacking one or more of the above character states . . . . . 24

24
return to couplet #23
 * Smaller species (HL ≤ 0.76, HW ≤ 0.68, ML ≤ 1.00); eye usually smaller (EL ≤ 0.12), with 2–7 ommatidia at greatest diameter (Couplet Figure 24. A, B); lateral margin of hypostomal bridge tapering to a point, never visible in profile view (Couplet Figure 6. D-F) . . . . . 25


 * Larger species (HL ≥ 0.80, HW ≥ 0.70, ML ≥ 1.02); eye usually larger (EL ≥ 0.11), with 5–11 ommatidia at greatest diameter (Couplet Figure 24. C); lateral margin of hypostomal bridge usually broadly rounded and somewhat projecting, often visible in profile view (Couplet Figure 6. C) . . . . . 29

25
return to couplet #24
 * Eye small (EL 0.04–0.08, REL 8–14), subcircular, with 2–5 ommatidia at greatest diameter (Couplet Figure 24. A) . . . . . 26


 * Eye larger (EL 0.09–0.12, REL 15–21), more oval-shaped, with 4–7 ommatidia at greatest diameter (Couplet Figure 24. B) . . . . . 27

26
return to couplet #25
 * Sculpture on face (and much of mesosoma) consisting of an even distribution of short longitudinal rugulae (Couplet Figure 26. A); body color a mottled yellow-brown (often pale yellow), with patches of darker brown; median clypeal lobe in full-face view visible and well developed (Couplet Figure 26. A); anterior clypeal margin with a shallow median emargination (northern Mexico) . . . . . Stenamma lagunum


 * Face densely sculptured and mostly rugoreticulate (Couplet Figure 26. B, C); mesosoma densely sculptured with punctae, rugae, and/or rugoreticulae; body color usually a darker orange-brown; clypeus in full-face view appearing very short, with median lobe nearly invisible due its dorsoventral orientation (Couplet Figure 26. B, C); anterior clypeal margin often with a deep median excision (Couplet Figure 26. B), but sometimes only with a very weak median depression (Couplet Figure 26. C) (Mexico to Honduras) . . . . . Stenamma excisum

27
return to couplet #25
 * Anterior clypeal margin either entire, or with a nearly imperceptible median notch (Couplet Figure 11. A), (Couplet Figure 27. A); dorsum of promesonotum either rugoreticulate, or with many irregular rugulae (Couplet Figure 27. B); petiolar node often broadly rounded and pointing distinctly posteriad (Couplet Figure 27. C) (southern Mexico to Guatemala) . . . . . Stenamma nonotch


 * Anterior clypeal margin not as above (Couplet Figure 17. D, G); dorsum of promesonotum with relatively dense longitudinal rugulae/carinulae (Couplet Figure 17. E, H); petiolar node not as above (Couplet Figure 17 F, I) . . . . . 28

28
return to couplet #27
 * Anterior clypeal margin with a shallow, but distinct median emargination (Couplet Figure 27. D); petiole usually appearing more elongate (Couplet Figure 27. F); petiolar node usually sharper and pointing more vertically; pilosity on gastral tergites longer and mostly forming a relatively sparse layer of suberect setae, only sometimes with decumbent setae (Couplet Figure 27. F); metafemur relatively longer (MFI 96–104) (southern Mexico to Honduras) . . . . . Stenamma ignotum


 * Anterior clypeal margin forming 2 small blunt teeth, which straddle the midline (Couplet Figure 27. G); petiole more compact, with the node less sharp and pointing more strongly posteriad (Couplet Figure 27. I); pilosity on gastral tergites somewhat shorter and usually distinctly bilayered, with a layer of suberect setae, and a layer of decumbent setae (Couplet Figure 27. G); metafemur relatively shorter (MFI 104–110) (Honduras to Nicaragua) . . . . . Stenamma picopicucha

29
return to couplet #24
 * Propodeal spines long and slender (Couplet Figure 21. E) (SSL 0.17–0.22, PSI 1.9–2.2); face with a dense fan of carinulae extending out from frontal lobes toward posterior and lateral margins of head (Couplet Figure 29. A); postpetiole appearing somewhat anteroposteriorly compressed (Couplet Figure 21. E) (southern Mexico) . . . . . Stenamma leptospinum (part)


 * Propodeal spines tuberculate to short (Couplet Figure 21. D) (SSL 0.09–0.19, PSI 1.0–1.6); face sculpture variable, but usually mostly rugoreticulate, and never densely carinulate (Couplet Figure 29. B, C); postpetiole usually more circular, not anteroposteriorly compressed (Couplet Figure 21. D) (Mexico to Nicaragua) . . . . . Stenamma manni (part)

30
return to couplet #11
 * Posterior ¼ or more of face smooth and shiny (Couplet Figure 30. A, B) . . . . . 31


 * Face completely sculptured, mostly rugoreticulate (Couplet Figure 30. C, D) . . . . . 33

31
return to couplet #30
 * Promesonotum in profile with relatively sharp transitions between anterior and dorsal faces, and between pronotum and mesonotum (Couplet Figure 31. B); pilosity on gastral tergites forming a layer of stout suberect setae, and a sparse layer of decumbent setae (Couplet Figure 31. C); face and pronotum almost completely smooth and shiny (Couplet Figure 31. A, B) (southern Mexico) . . . . . Stenamma andersoni


 * Promesonotum in profile more smoothly rounded; pilosity on gastral tergites variable, but without stout setae; face and pronotum sculpture variable . . . . . 32

32
return to couplet #31
 * Postpetiole in profile bulging and distinctly larger than petiolar node (Couplet Figure 32. A) (PPH 0.20–0.25, PPW 0.22–0.27, PPH/PH 0.96–1.14); eye larger (EL 0.11–0.16); face sculpture variable, but usually mostly smooth and shiny, with some carinulae around frontal lobes and anterolateral margins of head (Couplet Figure 30. A) (Couplet Figure xx); larger species (HL 0.67–0.86, HW 0.57–0.76, ML 0.84–1.09) (southern Mexico to Honduras) . . . . . Stenamma maximon (part)


 * Postpetiole smaller, about same size as petiolar node (Couplet Figure 32. B, C) (PPH 0.14–0.19, PPW 0.15–0.20, PPH/PH 0.79–0.97); eye smaller (EL 0.07–0.12); face sculpture usually more developed, with carinulae, punctae, and occasional rugoreticulae (Couplet Figure 30. B); smaller species (HL 0.55–0.72, HW 0.46–0.64, ML 0.66–0.85) (southern U.S.A. to Mexico) . . . . . Stenamma huachucanum (part)

33
return to couplet #30
 * Pilosity on gastral tergites predominately suberect and relatively sparse (Couplet Figure 33. A, B); decumbent setae if present very sparse . . . . . 34


 * Pilosity on gastral tergites shorter, denser, and usually distinctly bilayered, with a layer of suberect setae and an equally dense layer of decumbent setae (Couplet Figure 33. C-E) . . . . . 35

34
return to couplet #33
 * Entire face and most of mesosoma densely punctate, or densely carinulate (longitudinal orientation on face), or intermediate, with carinulae emerging from borders of punctae (Couplet Figure 34. A-C); eye larger (EL 0.15–0.18, REL 20–25), with 8–9 ommatidia at greatest diameter; propodeal spines absent to tuberculate, shorter (SSL 0.09–0.11, PSI 0.9–1.2) (Mexico to Honduras) . . . . . Stenamma stictosomum


 * Face less densely sculptured, usually mostly rugoreticulate, but sometimes sculpture more polished, with reticulae indistinct (Couplet Figure 34. D, E); eye smaller (EL 0.10–0.15, REL 18–22), with 5–8 ommatidia at greatest diameter; propodeal spines tuberculate to short, longer (SSL 0.08–0.16, PSI 1.1–1.8) (Mexico) . . . . . Stenamma vexator

35
return to couplet #33
 * Propodeal declivity in profile forming a broadly sinuous connection between propodeal spine and propodeal lobe (Couplet Figure 35. A) (southern Mexico [Oaxaca, Veracruz]) . . . . . Stenamma connectum


 * Propodeal declivity in profile straighter, leaving propodeal spine and lobe separated as distinct features (Couplet Figure 35. B), (Couplet Figure 36. A-F) . . . . . 36

36
return to couplet #35
 * Petiole in profile appearing longer and more gracile, with node either domelike and almost completely smooth and shiny (Couplet Figure 36. A), or small and somewhat compressed dorsoventrally (Couplet Figure 36. B); pronotum mostly sculptured, with punctae on side (Couplet Figure 36. A, B), and rugae or rugoreticulae on dorsum; frontal lobes often (but not always) distinctly expanded, covering the torular lobes in full-face view (FLD 0.15–0.25, FLI 28–46); propodeal spines present, short to medium length (SSL 0.11–0.17, PSI 1.6–2.1) . . . . . 37


 * Petiole in profile usually appearing shorter, more compact, and sometimes more robust, with node only shiny on anterior face and usually of moderate size (Couplet Figure 36. C-F); side of pronotum variably sculptured, often mostly smooth, and usually not punctate (Couplet Figure 36. C-F); frontal lobes almost always of average width, and never completely covering torular lobes in fullface view (FLD 0.11–0.20, FLI 23–31); propodeal spines variable, usually shorter (SSL 0.06–0.14, PSI 1.0–1.8) . . . . . 38

37
return to couplet #36
 * Petiole relatively longer (PL/HW 0.60–0.68); petiolar and postpetiolar nodes mostly smooth and shiny (Couplet Figure 36. A); postpetiole relatively smaller and appearing more shield-like (PPH/PH 0.75–0.84); scape and metafemur relatively shorter (SI 82–89, MFI 102–109); larger species (HL 0.65–0.76, HW 0.54–0.66, ML 0.81–0.99) (southern Mexico to Honduras) . . . . . Stenamma hojarasca


 * Petiole relatively shorter (PL/HW 0.53–0.59); petiolar and postpetiolar nodes smooth only on anterior faces; postpetiole relatively larger (Couplet Figure 36. B) (PPH/PH 0.85–0.91); scape and metafemur relatively longer (SI 92–104, MFI 84–95); smaller species (HL 0.61–0.68, HW 0.51–0.59, ML 0.75–0.82) (Honduras) . . . . . Stenamma catracho

38
return to couplet #36
 * Postpetiole in profile bulging and distinctly larger than petiolar node (Couplet Figure 32. A), (Couplet Figure 36. C) (PPH 0.20–0.25, PPW 0.22–0.27, PPH/PH 0.96–1.14); eye larger (EL 0.11–0.16), with 6–8 ommatidia at greatest diameter (southern Mexico to Honduras) . . . . . Stenamma maximon (part)


 * Postpetiole in profile smaller, about same size as petiolar node or smaller (Couplet Figure 36. D-F) (PPH 0.12–0.20, PPW 0.13–0.22, PPH/PH 0.79–1.04); eye smaller (EL 0.07–0.12), with 4–8 ommatidia at greatest diameter (usually ≤ 6) . . . . . 39

39
return to couplet #36
 * Head and mesosoma dark red-brown to orange-brown, with appendages a distinctly lighter orange- to yellow-brown (Couplet Figure 39. A); basal margin of mandible with basal depression, shallow or deep (Couplet Figure 11. F); eye often relatively smaller (REL 12–17); larger species (HL 0.63–0.83, HW 0.54–0.73, ML 0.76–1.09 PrW 0.37–0.50) (southern Mexico to Honduras) . . . . . Stenamma ochrocnemis


 * Body and appendage color less contrasting, generally dark to light brown (Couplet Figure 39. B); basal margin of mandible with basal depression shallow, never deep; eye often relatively larger (REL 14–21); smaller species (HL ≤ 0.72, HW ≤ 0.64, ML ≤ 0.85, PrW ≤ 0.41) . . . . . 40

40
return to couplet #39
 * Pronotum usually longitudinally rugose on most of dorsum and upper half of side, with small patches of smooth cuticle on middle of dorsum and lower half of side, but sometimes dorsum completely rugose or mostly smooth; propodeal spines tuberculate to short, often relatively longer (PSI 1.2–1.8); petiole compact, with a relatively small node that points slightly posteriad (Couplet Figure 36. E), (Couplet Figure 39. B) (note geography is easiest way to separate species in this couplet) (southern Mexico [Chiapas] to Nicaragua) . . . . . Stenamma crypticum


 * Pronotum sculpture variable, but usually not as above; propodeal spines absent or tuberculate, often relatively shorter (PSI 1.0–1.4); petiole variable, but often more elongate, or with the petiolar node distinctly enlarged and pointing vertically (Couplet Figure 36. F) (southern U.S.A. to southern Mexico [Oaxaca]) . . . . . Stenamma huachucanum (part)

41
return to couplet #11
 * Mesosoma in profile somewhat elongate, with metanotal groove wide, shallow, and indistinct, and propodeal dorsum markedly long and flat (Couplet Figure 41. A); anterior clypeal margin in full-face view with a deep uneven median emargination (Couplet Figure 41. B); basal tooth of mandible very robust and well-defined; eye relatively small (EL 0.09–0.11, REL 13–15), subcircular, with 5–6 ommatidia at greatest diameter (Honduras to Nicaragua) . . . . . Stenamma monstrosum


 * Lacking one or more of the above characters states . . . . . 42

42
return to couplet #41
 * Eye usually larger (EL 0.09–0.18, REL 18–29), with 6 or more ommatidia at greatest diameter (note other characterisctics of this species highly variable) (Nicaragua to Ecuador) . . . . . Stenamma schmidti (part)


 * Eye usually smaller (EL 0.05–0.14, REL 10–20), with 5 or fewer ommatidia at greatest diameter (southern Mexico to Nicaragua) . . . . . 43

43
return to couplet #42
 * Anterior 4/5 of face sculptured with short evenly spaced carinulae or rugulae (longitudinal in orientation), remaining posterior surface smooth and shiny (Couplet Figure 43. A); pilosity on gastral tergites forming a layer of longer suberect setae and a sparse layer of shorter decumbent setae, all setae of moderate thickness (Couplet Figure 44. A); larger species (HL 0.62–0.73, HW 0.56–0.70, ML 0.77–0.89) (Nicaragua) . . . . . Stenamma sandinista


 * Face completely sculptured, mostly rugoreticulate (Couplet Figure 43. B, C); gastral pilosity variable, but not as above (Couplet Figure 44. B, C); usually smaller species (HL ≤0.69, HW ≤0.59, ML ≤0.82) (southern Mexico to Honduras) . . . . . 44

44
return to couplet #43
 * Pilosity on gastral tergites forming a short layer of dense decumbent to appressed setae and a sparse layer of short suberect setae (Couplet Figure 44. B); propodeal spines tuberculate to short, longer (SSL 0.07–0.14, PSI 1.5–2.3); eye slightly smaller (EL 0.05–0.09, REL 10–16), subcircular, with 3–5 ommatidia at greatest diameter; scape and metafemur relatively shorter (SI 81–92, MFI 107–119); frontal lobes, not expanded outward (FLD 0.11–0.14, FLI 22–27) (southern Mexico to Honduras) . . . . . Stenamma saenzae


 * Pilosity on gastral tergites forming a layer of stout suberect setae and a very sparse layer of appressed setae (Couplet Figure 44. C); propodeal spines reduced to sharp angles or small tubercles, shorter (SSL 0.07–0.09, PSI 1.2–1.4); eye larger (EL 0.08–0.10, REL 15–18), more oval-shaped, with 4–5 ommatidia at greatest diameter; scape and metafemur longer (SI 90–99, MFI 97–104); frontal lobes slightly expanded outward (FLD 0.14–0.15, FLI 28–31) (Honduras) . . . . . Stenamma nanozoi