Key to Afrotropical Strumigenys

This worker key is based on: Bolton, B. 2000. The ant tribe Dacetini. Memoirs of the American Entomological Institute. 65:1-1028.

Bolton noted - Three species (Strumigenys adrasora, Strumigenys helytruga, Strumigenys rukha) may be ambiguously keyed at couplet 1, either because the preocular notch is very small or the species shows some variation in development of the character. For convenience these species are keyed through each lug of the couplet.

This key is from a revision that included the now synonymized genus Pyramica. Therefore there are two keys that treat two sets of Strumigenys species, the key found below and a key to Afrotropical Pyramica.

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1

 * Preocular notch present: ventrolateral margin of the head, and sometimes also side of head, impressed to deeply indented immediately in front of the eye, the indentation varying from a feeble impression in the ventrolateral margin to a notch so deep that the anterior portion of the eye is detached from the side of the head . . . . . 2


 * Preocular notch absent: ventrolateral margin of the head continuous to the anterior margin of the eye, without trace of an impression or indentation of the ventrolateral margin immediately in front of the eye . . . . . 23

2
return to couplet #1
 * Left mandible with 1 preapical tooth . . . . . 3


 * Left mandible with 2 preapical teeth . . . . . 6

3
return to couplet #2
 * Leading edge of scape with several hairs that are curved toward the base of the scape. Pronotal humeral hair straight, stiff and stout, remiform to feebly clavate. (Ethiopia, Kenya) . . . . . Strumigenys londianensis


 * Leading edge of scape with all hairs curved or inclined toward the apex of the scape. Pronotal humeral hair fine and flagellate . . . . . 4

4
return to couplet #3
 * Cephalic dorsum with 6 short erect simple hairs: a transverse row of 4 close to occipital margin and a pair close to highest point of vertex. Apical fork of left mandible without an intercalary small tooth or denticle between the spiniform fork teeth. Smaller species with longer mandibles, HW 0.36-0.41, MI 55-65. (Cameroun, Equatorial Guinea, Gabon, Zaire, Angola) . . . . . . Strumigenys bernardi


 * Cephalic dorsum without erect simple hairs. Apical fork of left mandible with an intercalary small tooth or denticle between the spiniform fork teeth. Larger species with shorter mandibles, HW 0.50 - > 0.70, MI 51-55 . . . . . 5

5
return to couplet #4
 * Large species, HL 1.00 or more; maximum length of hind femur > 0.80. Anterior pronotal margin without a pair of hairs between the flagellate humeral hairs. Ventral carina of petiole expanded anteriorly into a broadly triangular obtuse lobe. (Burundi) . . . . . Strumigenys transenna


 * Smaller species, HL < 1.00; maximum length of hind femur < 0.65. Anterior pronotal margin with a pair of erect stouter hairs between the humeral flagellate hairs. Ventral carina of petiole not expanded anteriorly into a broadly triangular obtuse lobe. (Zaire, Rwanda, Burundi, Uganda, Ethiopia) . . . . . Strumigenys sarissa

6
return to couplet #2
 * Preocular notch on each side continued onto ventral surface of head as a transverse impression or groove of varying length, which extends toward but does not reach the midline; this preocular impression situated posterior to the postbuccal groove or impression and independent of it . . . . . 7


 * Preocular notch on each side not continued onto ventral surface of head, the ventral surface convex and, except for the notch in the ventrolateral margin, without transverse preocular impressions that extend toward the midline posterior to the postbuccal groove or impression . . . . . 16

7
return to couplet #6
 * Apical fork of left mandible with a strong intercalary tooth and also a smaller denticle between the spiniform fork teeth. Cephalic dorsum without standing hairs close to occipital margin. With head in full-face view the upper scrobe margin strongly notched above the eye. Large species, HW > 0.60. Preapical teeth about equal in size or the distal somewhat larger than the proximal. (Ghana, Nigeria, Gabon) . . . . . Strumigenys cacaoensis


 * Apical fork of left mandible without trace of any intercalary tooth or denticle between the spiniform fork teeth. Cephalic dorsum with 2-4 standing hairs close to occipital margin. With head in full-face view the upper scrobe margin continuous above the eye. Smaller species, HW < 0.60. Preapical teeth with the distal shorter than the proximal . . . . . 8

8
return to couplet #7
 * Scape relatively long, SI 79-92 . . . . . 9


 * Scape relatively short, SI 64-74 . . . . . 11

9
return to couplet #8
 * Mandibles in full-face view and at full closure more or less straight, not conspicuously bowed outwards. On left mandible the distal preapical tooth about half the length of the proximal or slightly more, but stout and distinctly dentiform. Larger species, HW 0.42-0.52. (Cosmopolitan tramp species; very widespread in Afrotropical region, occurring as introduction in glasshouses etc. in Palaearctic) . . . . . Strumigenys rogeri


 * Mandibles in full-face view and at full closure conspicuously bowed outwards. On left mandible the distal preapical tooth much less than half the length of the proximal, sometimes reduced to a mere denticle, not stout. Smaller species, HW 0.36-0.41 . . . . . 10

10
return to couplet #9
 * Dorsum of propodeum densely reticulate-punctate and dull. (Cameroun, Equatorial Guinea, Gabon, Zaire, Angola) . . . . . Strumigenys bernardi


 * Dorsum of propodeum smooth and shining. (Ivory Coast, Ghana, Nigeria) . . . . . Strumigenys vazerka

11
return to couplet #8
 * Pronotal humeral hair absent . . . . . 12


 * Pronotal humeral hair present, flagellate . . . . . 13

12
return to couplet #11
 * Eye very large, its maximum diameter nearly twice the maximum width of the scape. Cephalic dorsum without a pair of simple standing hairs just in front of highest point of vertex. In profile ventral spongiform appendage of petiole a deep curtain, almost as deep as peduncle at its midlength. (Botswana, South Africa) . . . . . Strumigenys pretoriae


 * Eye smaller, its maximum diameter subequal to the maximum width of the scape. Cephalic dorsum with a pair of simple standing hairs just in front of highest point of vertex. In profile ventral spongiform appendage of petiole a narrow crest, less than half as deep as peduncle at its midlength. (Guinea, Ivory Coast, Ghana, Nigeria, Cameroun, Gabon, Zaire, Angola, Sudan, Central African Republic) . . . . . Strumigenys petiolata

13
return to couplet #11
 * Maximum diameter of eye equal to or only fractionally greater than the maximum width of the scape. Distal preapical tooth of left mandible short, separated from the proximal by a distance which is at least equal to the length of the distal tooth but which is sometimes more . . . . . 14


 * Maximum diameter of eye distinctly greater than the maximum width of the scape. Distal preapical tooth of left mandible long, separated from the proximal by a distance which is distinctly less than the length of the distal tooth . . . . . 15

14
return to couplet #13
 * Disc of postpetiole (when clean) usually very finely longitudinally superficially sculptured, only rarely smooth. With head in ventral view preocular impression broad and shallow, with poorly defined margins. (South Africa, Tanzania) . . . . . Strumigenys faurei


 * Disc of postpetiole (when clean) usually smooth and shining, only rarely with traces of superficial sculpture. With head in ventral view preocular impression narrow, with sharply defined margins. (Guinea, Ivory Coast, Ghana, Togo, Nigeria) . . . . . Strumigenys rufobrunea

15
return to couplet #13
 * Preocular impression on ventral surface of head forming a parallel-sided groove that is narrower than the maximum diameter of the eye; the edges of the groove sharply defined. (Zimbabwe) . . . . . Strumigenys shaula


 * Preocular impression on ventral surface of head forming a broad dish-like concavity that is at least as broad as the maximum diameter of the eye and usually broader; the edges of the impression are rounded and not sharply defined. (Burundi, Zaire, Tanzania) . . . . . Strumigenys dromoshaula

16
return to couplet #6
 * Eye small, with only 8 ommatidia in total. Cephalic dorsum with only a single pair of standing hairs, close to midline near occipital margin. (Angola) . . . . . Strumigenys helytruga


 * Eye with more than 8 ommatidia in total. Cephalic dorsum with 4 or 6 standing hairs . . . . . 17

17
return to couplet #16
 * Pronotal humeral hair absent. (Cameroun, Gabon) . . . . . Strumigenys totyla


 * Pronotal humeral hair present, flagellate . . . . . 18

18
return to couplet #17
 * In full-face view projecting hairs on leading edge of scape large and broadly spoon-shaped, about equal in size to the large broadly spoon-shaped hairs that fringe the upper scrobe margin. Cephalic dorsum with 4 stoutly remiform erect hairs, in a transverse row close to occipital margin; without a pair near highest point of vertex. Upper scrobe margin with a broad lamellate rim or flange. (Cameroun, Zaire) . . . . . Strumigenys xenohyla


 * In full-face view projecting hairs on leading edge of scape slender, either distinctly narrower than those that fringe the upper scrobe margin or with hairs in both places conspicuously slender, spatulate to narrowly elongate spoon-shaped. Cephalic dorsum with 6 short simple erect hairs, a transverse row of 4 close to occipital margin and a pair near highest point of vertex. Upper scrobe margin with a narrow cariniform rim or flange . . . . . 19

19
return to couplet #18
 * With head in full-face view the closed mandibles not bowed outwards; greatest distance across mandibles is close to base. In same view each mandible gradually increases in width from level of proximal preapical tooth to close to base; outer margin of mandible abruptly inflected at extreme base. (Tanzania) . . . . . Strumigenys percrypta


 * With head in full-face view the closed mandibles bowed outwards; greatest distance across mandibles is at or distal of the midlength. In same view each mandible approximately the same width from level of proximal preapical tooth to close to base, or gradually narrows basally; outer margin of mandible not abruptly inflected at extreme base . . . . . 20

20
return to couplet #19
 * In profile the area of the ventral postpetiolar spongiform lobe conspicuously much less than the visible area of the disc. Lamella on declivity of propodeum very narrow or vestigial, the tooth free or nearly free of the lamella. Ventral appendage of petiole reduced to a narrow non-spongiform cuticular carina. (Zaire, Rwanda, Burundi, Uganda) . . . . . Strumigenys adrasora


 * In profile the area of the ventral postpetiolar spongiform lobe equaling or exceeding the visible area of the disc. Lamella on declivity of propodeum broad, engaging half or more of the length of the tooth. Ventral appendage of petiole a spongiform strip or curtain . . . . . 21

21
return to couplet #20
 * With postpetiole in dorsal view spongiform material is visible projecting laterally at and in front of the midlength of the side of the disc. (Uganda, Kenya) . . . . . Strumigenys rukha


 * With postpetiole in dorsal view projecting spongiform material is restricted to the apices of the posterior transverse collar and does not occur in front of the midlength of the side of the disc . . . . . 22

22
return to couplet #21
 * Distal preapical tooth on left mandible greater than half the length of the proximal; length of the latter usually less than the distance separating it from the apicodorsal tooth, at most the two subequal. Scape shorter, SI 65-69. Occipital margin broadly and shallowly impressed. (Cameroun, Zaire, Angola) . . . . . Strumigenys relahyla


 * Distal preapical tooth on left mandible less than half the length of the proximal; the latter spiniform and its length distinctly greater than the distance separating it from the apicodorsal tooth. Scape longer, SI 70-74. Occipital margin narrowly and deeply impressed. (Zimbabwe) . . . . . Strumigenys dyshaula

23
return to couplet #1
 * Antenna with 4 segments, the first funicular segment followed directly by the 2-segmented club. Clypeus anteriorly very broad, in full-face view width across anterolateral angles is greater than SL. With head in full-face view the dorsolateral margin with a short stiff apicoscrobal hair. (Pan tropical tramp species) . . . . . Strumigenys emmae


 * Antenna with 5 or 6 segments, the first funicular segment separated from the 2- segmented club by one or two much smaller segments. Clypeus anteriorly narrow, in full-face view width across anterolateral angles is much less than SL. With head in full-face view the dorsolateral margin without an apicoscrobal hair . . . . . 24

24
return to couplet #23
 * Left mandible with 1 preapical tooth . . . . . 25


 * Left mandible with 2 preapical teeth . . . . . 29

25
return to couplet #24
 * Right mandible with 1 preapical tooth. (Zimbabwe, South Africa) . . . . . Strumigenys irrorata


 * Right mandible with 2 preapical teeth . . . . . 26

26
return to couplet #25
 * Apical fork of left mandible with an intercalary denticle between the spiniform teeth. Dorsum of head without a transverse row of 4 standing hairs close to the occipital margin. (Zaire, Burundi, Uganda, Kenya) . . . . . Strumigenys katapelta


 * Apical fork of left mandible without an intercalary denticle between the spiniform teeth. Dorsum of head with a transverse row of 4 standing hairs close to the occipital margin and with an erect pair situated close to the highest point of the vertex . . . . . 27

27
return to couplet #26
 * Pronotal humeral hair straight, stout and thickly clavate. (Cameroun, Gabon) . . . . . Strumigenys paranax


 * Pronotal humeral hair flagellate, long and fine . . . . . 28

28
return to couplet #27
 * With head in full-face view the mandible of approximately equal width from the proximal preapical tooth to near the extreme base. In same view upper scrobe margins shallowly convex, evenly divergent posteriorly; CI 71-77. Cephalic ground-pilosity on vertex behind level of frontal lobes narrowly spatulate, inconspicuous, narrower than hairs that fringe upper scrobe margin. (Cameroun, Equatorial Guinea, Gabon, Zaire, Angola, Central African Republic, Uganda) . . . . . Strumigenys dextra


 * With head in full-face view the mandible increasing in width from the proximal preapical tooth to near the extreme base. In same view upper scrobe margins strongly convex, flaring posteriorly; CI 84. Cephalic ground-pilosity on vertex behind level of frontal lobes spoon-shaped, conspicuous, broader than hairs that fringe upper scrobe margin. (South Africa) . . . . . Strumigenys rakkota

29
return to couplet #24
 * Katepisternum sculptured, reticulate to reticulate-punctate; metapleuron and side of propodeum also extensively to entirely sculptured . . . . . 30


 * Katepisternum mostly to entirely smooth; metapleuron and side of propodeum usually with extensive smooth patches, only very rarely entirely sculptured . . . . . 32

30
return to couplet #29
 * Apicoventral tooth of fork of left mandible subtended by a minute denticle and a ventrobasal adventitious tooth that is about half the length of the apicoventral tooth. Disc of postpetiole smooth. Scape shorter, SI 57-63 . . . . . 31


 * Apicoventral tooth of fork of left mandible without additional teeth arising from its ventrobasal surface or at most with an extremely minute denticle-like point at the extreme base. Disc of postpetiole finely reticulate-punctate. Scape longer, SI 79. (Tanzania) . . . . . Strumigenys didyma

31
return to couplet #30
 * Pronotal humeral hair present, stout and straight, directed laterally and clavate apically. Dorsolateral margin of promesonotum with a row of 4-5 short clavate standing hairs. Dorsum of petiole node weakly transversely striate. (Ghana, Nigeria) . . . . . Strumigenys pallestes


 * Pronotal humeral hair absent. Dorsolateral margin of promesonotum without standing hairs. Dorsum of petiole node punctate. (South Africa) . . . . . Strumigenys marleyi

32
return to couplet #29
 * Pronotal humeral hair absent . . . . . 33


 * Pronotal humeral hair present . . . . . 37

33
return to couplet #32
 * Leading edge of scape grossly expanded into a striking and very conspicuous anteriorly projecting lobe; maximum diameter of scape 0.50 X ML or more. (Uganda, Cameroun, Gabon) . . . . . Strumigenys tetraphanes


 * Leading edge of scape not expanded into a gross projecting lobe; maximum diameter of scape less than 0.50 X ML . . . . . 34

34
return to couplet #33
 * Scape broadest proximal of the midlength, thereafter evenly tapering to the apex. Mandible in full-face view broader at level of proximal preapical tooth than at base. Mandibles and scape longer, head narrower, MI 48-50, SI 82-85, CI 67-71. (Ghana, Cameroun, Gabon) . . . . . Strumigenys korahyla


 * Scape broadest at or just distal of the midlength, narrowing both proximally and distally. Mandible in full-face view narrower at level of proximal preapical tooth than at base. Mandibles and scape shorter, head broader, MI 35-41, SI 54-75, CI 74-90 . . . . . 35

35
return to couplet #34
 * Larger species with relatively broad head and short scape, HW 0.62-0.69, CI 85-90, SI 54-59. (Gabon) . . . . . Strumigenys ultromalyx


 * Smaller species with relatively narrow head and longer scape, HW 0.39-0.46, CI 74-80, SI 65-75 . . . . . 36

36
return to couplet #35
 * Disc of postpetiole completely unsculptured, smooth and shining. Pronotal dorsum finely reticulate-punctate and with longitudinal rugulae that overlie the punctate component. (Kenya, Zimbabwe) . . . . . Strumigenys arnoldi


 * Disc of postpetiole longitudinally striolate to punctate-striolate, this sculpture usually denser toward sides of disc than at its centre. Pronotal dorsum finely reticulate-punctate, without overlying longitudinal rugulae. (Kenya, Tanzania) . . . . . Strumigenys omalyx

37
return to couplet #32
 * Funicular segments 2 and 3 vestigial and difficult to see, partially or entirely fused together and partially fused to segment 4, so that the funiculus appears to have only 3 segments in total. Combined length of funicular segments 2 and 3 less than half the length of segment 4 (the penultimate segment) . . . . . 38


 * Funicular segments 2 and 3 small but easily visible, not fused together nor fused to segment 4, the funiculus distinctly with 5 segments. Combined length of funicular segments 2 and 3 more than half the length of segment 4 (the penultimate segment) . . . . . 39

38
return to couplet #37
 * Width of lamellate flange that borders upper scrobe margin distinctly greater than the maximum diameter of the eye, approaching the maximum width of the scape. Petiole node in dorsal view as broad as long. (Cameroun, Zaire) . . . . . Strumigenys bitheria


 * Width of lamellate flange that borders upper scrobe margin distinctly less than the maximum diameter of the eye, only a fraction of the maximum width of the scape. Petiole node in dorsal view much broader than long. (Ivory Coast, Ghana, Gabon) . . . . . Strumigenys nimbrata