Key to the Afrotropical Aenictus

This key to the workers of Aenictus of the Afrotropics is based on Gomez (2022).

For more information on Afrotropical ants see Afrotropical ant genera including resources and keys and the Afrotropical Region Species List.

This key does not include Aenictus brutus, a new species within the Aenictus popeyei species group, described by Gómez et al. (2024) from Liberia. For differentiation from Aenictus popeyei, please refer to the individual species pages.

1

Head glassy smooth [Figure 2A]; femora with their distal halves expanded [Figure 2C] (Maximum width / minimum width ~ 3-4) . . . . . 2
Head alutaceus to heavily reticulated, matt [Figure 2B]; femora subcylindrical [Figure 2D] (Maximum width / minimum width < 2) . . . . . 7 (koloi group)

Gómez 2022. Figure 2.

2

return to couplet #1

Mandibles either linear or triangular, never with either a large blunt, rounded basal tooth nor with its basal half expanded and semi-spherical [Figure 1A, C, D, G, H] . . . . . 3
Mandibles massive, neither linear nor triangular, either with a large, blunt, rounded basal tooth separated from the rest by a depression (mitten-shaped) or with its basal half expanded and semi-spherical [Figure 1E, F] . . . . . 6

Gómez 2022. Figure 1.

3

return to couplet #2

Mandibles linear, leaving a gap between themselves and the clypeus when closed. Clypeus reduced to two triangular minute teeth between or beneath the antennal sockets [Figure 1C, D] . . . . . 11 (eugenii group)
Mandibles linear to triangular with no gap between themselves and the clypeus when mandibles closed. Clypeus usually with a row of minute triangular denticles, and never reduced to two triangular minute teeth between or beneath the antennal sockets [Figure 1A, G, H] . . . . . 4

4

return to couplet #3

Mandibles very long, crossing over at the mid-length when closed, each mandibular apex clearly reaching the opposite antennal insertion; apical tooth massive, usually without preapical tooth or denticles (Fig. E, below) . . . . . asantei group, one species: Aenictus asantei

Aenictus asantei

Mandibles linear to triangular, neither crossing over at the mid-length nor with each mandibular apex; preapical tooth and/or denticles may be present (Fig. 1-A and H, couplet #2) . . . . . 5

5

return to couplet #4

Mandibles linear, with three or four defined teeth. Clypeus reduced to a thin line, virtually not visible in frontal view [Figure 1H] . . . . . 12 (rixator group)
Mandibles triangular, always with more than 4 teeth or denticles in total. Dentition variable, usually with one apical tooth followed by a preapical tooth and/or a series of smaller denticles, but some species with an apical tooth followed by smaller well defined triangular teeth. Clypeus present as a narrow lamella or a row of triangular denticles, sometimes small and difficult to see when mandibles closed [Figure 1A] . . . . . 13 (rotundatus group)

6

return to couplet #2

Mandibles with basal half expanded and semi-spherical, surrounded by a thin cutting edge [Figure 1E] . . . . . popeyei group, one species: Aenictus popeyei

Aenictus popeyei

Mandibles with a conspicuous, blunt, large proximal tooth clearly separated from the rest of the mandible, mitten shaped [Figure 1F] . . . . . 9 (decolor group)

7

return to couplet #5

Numerous long, white, semierect to erect setae present on scapes, dorsum of mesosoma, petiole, postpetiole and femora. Petiole with clearly more than 10 setae [Figure 22C] . . . . . Aenictus susanae

Aenictus susanae

Scattered white, erect setae present on scapes, dorsum of mesosoma, petiole, postpetiole and femora. Petiole with 4 to 8 setae . . . . . 8

8

return to couplet #7

Subpetiolar process small, size similar to the prora, shaped as a quarter of ellipse with the vertical face facing forward, followed by an almost horizontal ovoid lamella [Figure 20C]; smaller size (HW< 0.60) . . . . . Aenictus koloi

Aenictus koloi

Subpetiolar process very developed, subrectangular and followed by a rectangular lamella usually inclined 45 degrees forward, the whole process clearly larger than the prora [Figure 24C]; larger size (HW>0.65) . . . . . Aenictus xegi

Aenictus xegi

9

return to couplet #8

Scapes relatively shorter, slightly surpassing three quarters of head length when laid back (SIL<80), smaller size (HL<0.70, WL<1.15) . . . . . Aenictus bidentatus

Aenictus bidentatus

Scapes relatively longer, distinctly surpassing three quarters of head length when laid back (SIL>80), larger size (HL>0.70, WL>1.15) . . . . . 10

10

return to couplet #9

Scapes reaching three quarters of the head length when laid back (80<SIL<95). Subpetiolar process subrectangular, volume slightly smaller than petiolar dome and of similar shape, displaced forward [Figure 7C] . . . . . Aenictus decolor

Aenictus decolor

Scapes almost reaching the occipital border when laid back (SIL>95). Subpetiolar process small and shaped as a quarter of ellipse, with its vertical line anteriorly located [Figure 9C]. . . . . Aenictus villiersi

Aenictus villiersi

11

return to couplet #3

Scapes with dense, reclined setae that are shorter than scape width, without erect to semierect setae that are much longer than maximum scape width [Figure 18A]; mesosoma covered with subequal reclined short setae, shorter than petiole height [Figure 18C]. Size clearly smaller (0.47<HW<0.63) . . . . . Aenictus mvuvii

Aenictus mvuvii

Scapes with erect to semierect setae that are much longer than maximum scape width [Figure 11A]; mesosoma covered with erect to semierect long setae, unequal in size, the longest clearly longer than petiole height [Figure 11C]. Size larger (0.63<HW<0.94) . . . . . Aenictus eugenii

Aenictus eugenii

12

return to couplet #5

Ridge separating dorso and posteropropodeum present and clearly visible projecting from the dorsal propodeal surface [Figure 30C]. Mandibles with three teeth similar in size . . . . . Aenictus rixator

Aenictus rixator

Ridge separating dorso and posteropropodeum absent, so dorso and posteroprodeum form a smooth continuous surface [Figure 28C]. Mandibles with an apical tooth followed by three smaller denticles . . . . . Aenictus mentu

13

return to couplet #5

Scapes relatively very short (SIL<58). If 58 <SIL< 62, then setae on the mesosoma semierect to erect, unequal and long mixed with shorter reclinated setae [Figure 57C] . . . . . 14 (mariae species complex, minima workers of Aenictus rotundatus with HW<0.46)
Scapes relatively longer (SIL ≥ 60, usually >62). If 58<SIL<62, then setae on the mesosoma reclinated and similar in length [Figure 52C] . . . . . 18 (rotundatus species complex)

14

return to couplet #13

SIL 58-60 . . . . . Aenictus rotundatus (part, exceptionally small minima workers with HW<0.46. Larger HW always SIL>62)
SIL <58, usually SIL <56 . . . . . 15

15

return to couplet #14

Lateral surfaces of mesonotum, propodeum, petiole and postpetiole covered with a white, short, dense pubescence, much shorter than setae on dorsal surfaces (best viewed in dorsal view) [Figure 39D] . . . . . Aenictus steindachneri

Aenictus steindachneri

Lateral surfaces of mesonotum, propodeum, petiole and postpetiole bare, setation restricted to some occasional isolated setae [Figure 54D]. . . . . 16

16

return to couplet #15

Dorsopropodeum densely sculptured, punctated-reticulated even in the minima workers as a faint reticulum [Figure 35D, Figure 34D]. Dorsopronotum with very dense pilosity, covered with more than 20 white short reclinated setae, without bare zones where cuticle is clearly seen [Figure 35C, Figure 35C] . . . . . Aenictus hitai

Aenictus hitai

Dorsopropodeum smooth, although some kind of shagreened sculpturation may be present laterally [Figure 32D, Figure 37D]. Dorsopronotum with very sparse pilosity, clearly with less than 20 white short setae, extensive zones bare where cuticle is clearly seen [Figure 32C, Figure 37C] . . . . . 17

17

return to couplet #16

Metanotal groove demarcated, slightly indented in profile and dorsal views; postpetiole with clearly defined anterior and posterior vertical faces, subrectangular with rounded angles and relatively higher (PPI: 113 [107-127]) [Figure 32C, D]. Western Africa . . . . . Aenictus boltoni

Aenictus boltoni

Metanotal groove not demarcated, mesopropodeal profile almost a straight line; postpetiole hemispherical, without anterior and posterior vertical faces and relatively lower (PPI: 138 [130-150]). Southern Africa [Figure 37C, D] . . . . . Aenictus mariae

Aenictus mariae

18

return to couplet #13

Setae adpressed everywhere [Figure 41A, C]. Clypeus with a row of very conspicuous long, conical teeth, much longer than wide, the two central smaller than the rest [Figure 41]. Subpetiolar process subrectangular, clearly lower than long, oriented 45° forward, mostly digit shaped [Figure 41C] . . . . . Aenictus congolensis

Aenictus congolensis

Setae from semierect to erect everywhere [Figure 44A, C]. Clypeus with a row of triangular teeth, about as long as wide [Figure 44E]. Subpetiolar process never digitiform and elongated, but ellipsoidal, followed or not by a lamella . . . . . 19

19

return to couplet #18

Scapes very long (SIL >80). Meatanotal groove in profile wide, rounded, U-shaped [Figure 54C] . . . . . Aenictus nyuyi

Aenictus nyuyi

Scapes short (SIL<75). Metanotal groove in profile not conspicuous, V-shaped as the mesonotum meets the propodeum at an angle [Figure 59A] . . . . . 20

20

return to couplet #19

Setae on dorsal surface of mesosoma reclined, very abundant and with similar length [Figure 32C, Figure 37C]; lateral surfaces of head covered with clearly more than 20 small, adpressed setae, the size of each about equal to the maximum scape width [Figure 32A, Figure 37A] . . . . . Aenictus jacki

Aenictus jacki

Setae on dorsal surface of mesosoma erect to semierect and scattered, unequal, with some setae clearly longer than petiole height [Figure 59C]; lateral surfaces of head almost bare, with clearly less than 20 long setae, the size of each clearly longer than the maximum scape width [Figure 59A] . . . . . 21

21

return to couplet #20

Head subquadrate (CI>95) [Figure 59A] with stouter mesosoma (WL/PRW<250) [Figure 59C, D] . . . . . Aenictus ugaduwensis

Aenictus ugaduwensis

Head more elongated (CI<93) [Figure 61A] with more slender mesosoma (WL/PRW>270) [Figure 61C, D] . . . . . 22

22

return to couplet #21

Dorso and posteropropodeum separated by a developed, horizontal ridge clearly visible in lateral view, so there is not a smooth transition into each other [Figure 61C]; in dorsal view this ridge projecting itself as a horizontal shelf, not reduced to a single line [Figure 61D]. Subpetiolar process elongated and without lamellae, usually a quarter ellipse with its vertical side anteriorly, overall size clearly smaller than petiolar node [Figure 61C] . . . . . Aenictus weissi

Aenictus weissi

Dorso and posteropropodeum not separated by a horizontal ridge, so having a continuous smooth transition into each other [Figure 44C]; if a continuous ridge is present laterally and dorsally, it’s weak and in dorsal view only a faint line, not projecting itself as a horizontal shelf [Figure 44D]. Subpetiolar process rounded and usually with a triangular to ellipsoidal lamella . . . . . 23