Key to Malagasy Strumigenys

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

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 Malagasy Pyramica.

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Strumigenys

1

 * With head in full-face view a preocular notch present, the ventrolateral margin of the head notched or indented immediately in front of the eye. With head in profile the preocular notch seen to continue vertically as a groove in the side of the head that extends towards the dorsal outline; in the same view preocular notch also seen to extend onto the ventral surface of the head as a transverse preocular groove that runs towards but does not reach the midline. An extremely deep and sharply defined post-buccal groove also present, extending across entire width of head immediately posterior of buccal cavity; postbuccal groove sharply separated from ventral preocular groove . . . . . 2


 * With head in full-face view a preocular notch absent, the ventrolateral margin of the head continuous to the anterior margin of the eye, without trace of a notch or indentation immediately in front of the eye. With head in profile side in front of eye without a vertical groove that extends towards the dorsal outline; in the same view without a transverse preocular groove on the ventral surface of the head. Postbuccal groove vestigial or at most a shallow transverse impression immediately posterior of buccal cavity . . . . . 23

2
return to couplet #1
 * With head in profile, upper scrobe margin ending, or at least becoming extremely indistinct, at about the level of the eye . . . . . 3


 * With head in profile, scrobe, and its dorsal margin, extending posteriorly well beyond level of eye . . . . . 9

3
return to couplet #2
 * Preapical teeth absent or at most a small spiniform denticle may be present immediately basal of apicodorsal tooth on right mandible. Apical fork of mandible subtended by a third, shorter spiniform tooth . . . . . 4


 * Preapical teeth present. Apical fork of mandible not subtended by a third spiniform tooth; at most the apicoventral tooth may have a minute spur or denticle at its ventral base . . . . . 7

4
return to couplet #3
 * With head in profile preocular groove meets and is interrupted by the upper scrobe margin before reaching the cephalic dorsum. Scapes relatively shorter, SI 78-86 . . . . . 5


 * With head in profile preocular groove extends uninterrupted to the cephalic dorsum, and is not interrupted by the upper scrobe margin. Scapes relatively longer, SI 91-132 . . . . . 6

5
return to couplet #4
 * Mesonotum with 1 pair of erect hairs on anterior margin. Cephalic dorsum with a transverse row of four erect hairs immediately in front of occipital margin . . . . . Strumigenys actis


 * Mesonotum with 2 pairs of erect hairs (can be worn). Cephalic dorsum with a transverse row of six erect hairs immediately in front of occipital margin . . . . . Strumigenys ampyx

6
return to couplet #4
 * Propodeal spines shorter, length of spine about equal to distance between bases of spines, distance between bases of spines measured distal to basal curvature. Dorsum of head sharply depressed behind vertex, forming a very shallow concave impression before occipital angles; in profile, outline of dorsal margin of occipital corners almost flat. Scapes relatively shorter, SI 91-106 . . . . . Strumigenys chilo


 * Propodeal spines long, much longer than distance between bases of spines. Dorsum of head evenly and gradually curved from vertex to posterior margin of occipital corner; in profile, outline of dorsal margin of occipital corners continuously and gradually curved, not flat. Scapes relatively longer, SI 115-132 . . . . . Strumigenys bibiolona

7
return to couplet #3
 * Large species, HL 1.25-1.45, HW 0.97-1.14. Mandible with truncated preapical teeth. Pronotal humeral hair absent. First gastral tergite and sternite without punctate sculpture or at most merely the extreme base of the tergite punctate, the sternite always smooth . . . . . Strumigenys grandidieri


 * Smaller species, HL 0.70-0.75, HW 0.55-0.59. Mandible with spiniform preapical teeth. Pronotal humeral hair present, stiff. First gastral tergite and sternite densely punctate over the anterior half or more of each sclerite . . . . . 8

8
return to couplet #7
 * Dorsum of petiole with at least 3 pairs of hairs. Propodeal spines broadly triangular. Propodeal declivity with a standing, posteriorly projecting hair at centre of lateral margin. Katepisternum smooth and shiny. Colour chocolate brown . . . . . Strumigenys dora


 * Dorsum of petiole with one pair of hairs. Propodeal spines narrowly triangular and almost spiniform. Propodeal declivity without standing hairs. Katepisternum reticulate-punctate. Colour orange brown . . . . . Strumigenys fanano

9
return to couplet #2
 * In full-face view apical portion of the inner margin of the mandible concave or scooped out. Mandible without defined preapical teeth; a rounded tumulus or rarely a minute acute denticle may be present on the proximal apex of the preapical concavity . . . . . Strumigenys dicomas


 * In full-face view apical portion of the inner margin of the mandible not scooped out or concave. Mandible with 1 or more sharply defined acute preapical teeth and/or denticles . . . . . 10

10
return to couplet #9
 * Left mandible with 2 preapical teeth and/or denticles . . . . . 11


 * Left mandible with 1 preapical tooth or denticle . . . . . 17

11
return to couplet #10
 * Pronotal humeral hair absent . . . . . 12


 * Pronotal humeral hair present . . . . . 14

12
return to couplet #11
 * Scape relatively long, SI > 90 . . . . . Strumigenys hilaris


 * Scape relatively short, SI < 90 . . . . . 13

13
return to couplet #12
 * Mesonotum with a single pair of erect hairs, on anterior margin. In profile, petiole node broadly triangular with a blunt apex . . . . . Strumigenys luca


 * Mesonotum with two pairs of erect hairs, a shorter pair posterior to pair on anterior margin. In profile, petiole node evenly convex . . . . . Strumigenys milae

14
return to couplet #11
 * Pronotal humeral hair flagellate. In profile preocular notch immediately in front of eye narrow, width of notch distinctly less than the maximum diameter of eye. (Cosmopolitan tramp species) . . . . . Strumigenys rogeri


 * Pronotal humeral hair stiffly erect, filiform. In profile preocular notch immediately in front of eye broad, width of notch approximately equal to the maximum diameter of eye . . . . . 15

15
return to couplet #14
 * Dorsolateral margin of head posteriorly without stiff erect hairs that are longer than hairs on leading edge of scape. Upper scrobe margin with a narrow projecting lamellate rim above vertical preocular groove on side of head. Mesonotum with a single pair of erect hairs, located on anterior margin . . . . . Strumigenys lysis


 * Dorsolateral margin of head posteriorly with 2-4 (usually 3) stiff erect hairs that are longer than hairs on leading edge of scape. Upper scrobe margin without a projecting lamellate rim above vertical preocular groove on side of head; scrobe margin weakly marginate to rounded. Mesonotum with one or two pairs of erect hairs . . . . . 16

16
return to couplet #15
 * Mesonotum with a single pair of erect hairs, on anterior margin . . . . . Strumigenys nambao


 * Mesonotum with two pairs of erect hairs, a shorter pair posterior to pair on anterior margin . . . . . Strumigenys norax

17
return to couplet #10
 * Head massive, broad, HW 1.28-1.65. Propodeal spines recurved anteriorly . . . . . Strumigenys vazimba


 * Head narrower, HW < 0.90. Propodeal spines not recurved anteriorly . . . . . 18

18
return to couplet #17
 * Pronotal humeral hair long, stiffly projecting, filiform . . . . . 19


 * Pronotal humeral hair absent . . . . . 20

19
return to couplet #18
 * Dorsolateral margin of head posteriorly with 2-3 stiff erect hairs that are longer than hairs on leading edge of scape. Head shorter and relatively broader, HL 0.80-0.88, CI > 80 . . . . . Strumigenys fronto


 * Dorsolateral margin of head posteriorly without stiff erect hairs that are longer than hairs on leading edge of scape. Head longer and relatively narrower, HL 0.95-1.00, CI < 70 . . . . . Strumigenys carisa

20
return to couplet #18
 * Anterior margin of mesonotum with 2 pairs of stout standing erect hairs, one pair situated slightly anterior and mesad of second pair at anterior lateral margin of mesonotum . . . . . Strumigenys ection


 * Anterior margin of mesonotum with only a single pair of erect hairs, situated at anterior lateral margin of mesonotum. Rarely, a second pair of hairs is present posterior to the first pair, situated at the midlength of the lateral margin of the mesonotum . . . . . 21

21
return to couplet #20
 * Upper scrobe margin with a distinct, broad lamellate rim or flange throughout its length. Basal half of scape distinctly and sharply swollen or more or less subcylindrical. Dorsum of head with a transverse row of 6 hairs close to the occipital margin . . . . . 22


 * Upper scrobe margin without a broad lamellate rim or flange throughout its length, lamellate rim when present limited to region above antennal insertion. Basal half of scape never sharply swollen, scape more or less subcylindrical. Dorsum of head with a transverse row of 4 or 6 erect hairs close to the occipital margin . . . . . Strumigenys sphera

22
return to couplet #21
 * With head in ventral view, posterior-lateral and lateral margins of postbuccal groove with a lamellate rim; posterior-lateral face of groove concave . . . . . Strumigenys admixta


 * With head in ventral view, posterior and lateral margins of postbuccal groove rounded to bluntly marginate; posterior-lateral face of groove never concave, more or less vertical or gently sloping . . . . . Strumigenys labaris

23
return to couplet #1
 * Leading edge of scape a dorsoventrally flattened convex lamella . . . . . 24


 * Leading edge of scape not a dorsoventrally flattened convex lamella; scape elongate and subcylindrical . . . . . 47

24
return to couplet #23
 * In full-face view the mandibles asymmetric, the left mandible with 3 long or spiniform teeth (including preapical and apical), the right with 4 such teeth. HL 0.55-0.70, MI 17-33. Eyes usually conspicuous, never with 4 or less ommatidia; if eyes small, then lower scrobe margin marginate, forming a sharp ridge with ventral surface of head . . . . . 25


 * In full-face view the mandibles symmetric, each with either 3 or 4 long or spiniform teeth. HL 0.37-0.71, MI 27-47. Eyes always small to minute (usually with 4 or less ommatidia); lower scrobe margin rounded, never forming a sharp ridge with ventral surface of head . . . . . 33

25
return to couplet #24
 * Dorsum of head with scattered punctures, the spaces between them smooth and shiny. Dorsum of promesonotum and petiole node smooth or with smooth surfaces between scattered punctures; without blanketing reticulate-punctate sculpture anywhere on the dorsum. Disc of postpetiole with scattered punctures or glassy smooth, without longitudinal sculpture . . . . . 26


 * Dorsum of head, and usually the dorsal surfaces of promesonotum and petiole node, entirely blanketed with dense fine reticulate-punctate to reticulate-granulate sculpture; without smooth spaces between scattered punctures. Disc of postpetiole usually with fine longitudinal striae or costulae, at least towards the sides . . . . . 30

26
return to couplet #25
 * Exposed cuticle of petiole node in dorsal view at least as long as broad, usually longer than broad. Pronotal disc as long as broad in dorsal view [length of pronotal disc measured from the anterior margin of the mesothoracic spiracle as seen in dorsal view to point at which the pronotum meets the cervical shield] . . . . . Strumigenys coveri


 * Exposed cuticle of petiole node in dorsal view conspicuously broader than long. Pronotal disc broader than long in dorsal view . . . . . 27

27
return to couplet #26
 * Cephalic dorsum with appressed spoon-shaped hairs on the lateral portions of the occipital lobes behind the level of the scrobes, these hairs as large as those that border the upper scrobe margins . . . . . Strumigenys gorgon


 * Cephalic dorsum -without appressed spoon-shaped hairs on the lateral portions of the occipital lobes; such hairs are however present bordering the upper scrobe margins . . . . . 28

28
return to couplet #27
 * Labrum with apical lobes each terminating in a projecting broad fan-like lamella of translucent thin cuticle and a short trigger hair mesad of fan-like lamella; trigger hairs often difficult to see. Base of first gastral sternite with a row of flat, broad, spatulate appressed hairs . . . . . Strumigenys dexis


 * Labrum with apical lobes each terminating in one or two curved trigger hairs, without a fan-like lamella of translucent cuticle. Base of first gastral sternite without flat appressed hairs . . . . . 29

29
return to couplet #28
 * Mesonotum without standing hairs. First gastral tergite entirely without standing hairs . . . . . Strumigenys rabesoni


 * Mesonotum with a single pair of short straight standing hairs. First gastral tergite with a single pair of straight standing hairs close to the base . . . . . Strumigenys peyrierasi

30
return to couplet #25
 * Erect short hairs entirely absent from dorsal surfaces of alitrunk, waist segments and first gastral tergite; hairs usually absent from cephalic dorsum, at most 1 pair of short simple hairs at occipital angles . . . . . 31


 * Erect short hairs present as follows: a transverse row of 4 across the cephalic dorsum close to the occipital margin, one pair on the mesonotum, one pair posteriorly on the petiole node, two pairs posteriorly on the postpetiole disc, at least a basal row on first gastral tergite . . . . . 32

31
return to couplet #30
 * Cephalic dorsum immediately behind clypeus with a transverse band of scale-like hairs, arranged in several irregular rows; cephalic dorsum without erect hairs. Dorsal surfaces of promesonotum and petiole node entirely blanketed with dense fine reticulate-punctate to reticulate-granulate sculpture. Disc of postpetiole with fine longitudinal striae or costulae, at least towards the sides. Promesonotum flat with bluntly marginate humeral angles . . . . . Strumigenys alperti


 * Cephalic dorsum immediately behind the clypeus without scale-like hairs; cephalic dorsum with 1 pair of short simple hairs at occipital angles. Dorsal surfaces of promesonotum and petiole node with only scattered fine reticulate-punctate sculpture. Disc of postpetiole without fine longitudinal striae or costulae. Promesonotum transversely convex dorsally with rounded humeral angles . . . . . Strumigenys carolinae

32
return to couplet #30
 * Postpetiolar disc finely longitudinally costulate. First gastral tergite without standing hairs between the apical and basal rows . . . . . Strumigenys wardi


 * Postpetiolar disc longitudinally reticulate-punctate, often with feeble longitudinal rugulae. First gastral tergite with standing hairs present between the apical and basal rows . . . . . Strumigenys sylvaini

33
return to couplet #24
 * Antenna with 4 segments . . . . . 34


 * Antenna with 6 segments . . . . . 38

34
return to couplet #33
 * Pronotal humeral hair present; looped, flagellate, or straight-clavate and projecting laterally . . . . . 35


 * Pronotal humeral hair absent . . . . . 37

35
return to couplet #34
 * Pronotal humeral hair looped or flagellate . . . . . Strumigenys micrans


 * Pronotal humeral hair straight-clavate . . . . . 36

36
return to couplet #35
 * Row of scale-like to broadly spoon-shaped hairs on upper scrobe margin not terminating in a more or less straight clavate apicoscrobal hair. Scape strongly back-curved, with an anteriorly proj ecting subbasal lobe at the bend; apex of lobe with a projecting hair that is broadly clavate, almost fan-like. Preapical tooth of mandible set at the midlength of the mandible . . . . . Strumigenys schuetzi


 * Row of scale-like orbicular hairs on upper scrobe margin terminating in a more or less straight clavate apicoscrobal hair. Scape slightly back-curved, leading edge broadening at midlength and convex, not lobe-like, with a row of spoon-shaped hairs. Preapical tooth of mandible set in the distal third of the mandible. (Pantropical tramp species) . . . . . Strumigenys emmae

37
return to couplet #34
 * Pronotal disc without distinct longitudinal costulae; with densely reticulate-punctate sculpture as on posterior dorsum of head . . . . . Strumigenys lutron


 * Pronotal disc with distinct longitudinal costulae and not sculptured as posterior dorsum of head; in between costulae, pronotum smooth or with fine punctulate sculpture . . . . . Strumigenys levana

38
return to couplet #33
 * Pronotal humeral hair present, stiffly remiform to thickly clavate and projecting laterally . . . . . 39


 * Pronotal humeral hair absent . . . . . 40

39
return to couplet #38
 * In profile, outline of alitrunk almost flat with a slight medial depression. Cephalic dorsum posterior of frontal lobes and along upper scrobe margin without hairs that are similar in shape to hairs on leading edge of scape. Lateral lobe on petiole very small and inconspicuous. Smaller, HL < 0.49, HW < 0.40 . . . . . Strumigenys alapa


 * In profile, outline of alitrunk convex in anterior half, more or less flat in posterior half; anterior mesonotal dorsum steeply descending to its posterior half. Cephalic dorsum posterior of frontal lobes and along upper scrobe margin with hairs that are distinctly narrower than hairs on leading edge of scape. Lateral lobe on petiole well developed. Larger, HL > 0.55, HW > 0.48 . . . . . Strumigenys manga

40
return to couplet #38
 * Left mandible usually with two distinct preapical teeth: a longer proximal tooth and a smaller distal tooth. Larger, HL 0.53-0.71, HW 0.58-0.68 . . . . . 41


 * Left mandible with only one distinct, long preapical tooth; a minute denticle may also be present distal of the spiniform preapical tooth. Smaller HL 0.40-0.49, HW 0.38-0.45 . . . . . 42

41
return to couplet #40
 * Cephalic dorsum posterior of frontal lobes and along upper scrobe margin without hairs that are similar in shape to hairs on leading edge of scape. Erect short, narrowly clavate hairs present on head, alitrunk and petiole . . . . . Strumigenys abdera


 * Cephalic dorsum posterior of frontal lobes and along upper scrobe margin with hairs that are similar in shape to hairs on leading edge of scape. Erect short, narrowly clavate hairs absent from head, alitrunk and petiole . . . . . Strumigenys heliani

42
return to couplet #40
 * Apical fork of mandible consisting of 3 spiniform teeth, with an intercalary denticle between the apicoventral tooth and apicomedian tooth. Dorsum of alitrunk, petiole, postpetiole and gaster blanketed with numerous broadly spoon-shaped to suborbicular hairs. In profile, peduncle of petiole forming a broad translucent cuticular keel ventrally; spongiform tissue limited to a narrow strip at apex of the keel. In profile ventral spongiform tissue on postpetiole forming a hollow triangular projection . . . . . Strumigenys adsita


 * Apical fork of mandible consisting of 2 spiniform teeth, without intercalary dentition between the fork teeth. Dorsum of alitrunk, petiole, postpetiole and gaster without numerous clavate to spoon-shaped hairs. In profile, peduncle of petiole normal, not forming a broad keel ventrally. In profile ventral spongiform tissue on postpetiole not hollow and triangular in outline . . . . . 43

43
return to couplet #42
 * Cephalic dorsum -with broad spoon-shaped to orbicular hairs present from posterior clypeal margin to occipital margin. Dorsum of petiole with a pair of broadly clavate to remiform hairs . . . . . Strumigenys bathron


 * Cephalic dorsum with clavate, spoon-shaped or orbicular hairs absent from posterior third of surface. Dorsum of petiole without a pair of broadly clavate to remiform hairs, at most with a pair of filiform to narrowly clavate hairs . . . . . 44

44
return to couplet #43
 * Mesonotum with a pair of short erect hairs on anterior margin. Base of first gastral tergite with a continuous row of sharply defined basal costulae . . . . . Strumigenys mola


 * Mesonotum without a pair of short erect hairs on anterior margin. Base of first gastral tergite with or without a continuous row of well developed basal costulae . . . . . 45

45
return to couplet #44
 * In profile width of lamella on propodeal declivity distinctly less than half the width of the ventral spongiform strip on the petiole, approximately equal to the width of eye. Base of first gastral tergite with a continuous row of well developed basal costulae . . . . . Strumigenys charino


 * In profile width of lamella on propodeal declivity approximately half the width of the ventral spongiform strip on the petiole. Base of first gastral tergite without a continuous row of sharply defined basal costulae . . . . . 46

46
return to couplet #45
 * Basigastral costulae fine, radiating on each side of a central clear area which is free of costulae; punctulate-reticulate sculpture on tergite restricted to region of basal costulae, remainder of tergite smooth . . . . . Strumigenys dolabra


 * Basigastral costulae short, sparse and not sharply defined, gastral tergite covered in punctulate- to granulate-reticulate sculpture, at least on lateral margins . . . . . Strumigenys toma

47
return to couplet #23
 * Apical fork of right mandible with 2 (occasionally 1) intercalary teeth between the spiniform apicodorsal and apicoventral teeth; each mandible with 1 preapical stout tooth. (Mauritius) . . . . . . Strumigenys agetos


 * Apical fork of right mandible without intercalary teeth or denticles between the spiniform teeth; each mandible with 2 preapical teeth or preapical teeth absent . . . . . 48

48
return to couplet #47
 * Apical fork of right mandible composed of 3 spiniform teeth; preapical teeth absent, or at most with a small subapical tooth or denticle on left mandible. Propodeal spines long slender and recurved . . . . . 49


 * Apical fork of right mandible composed of 2 spiniform teeth; each mandible with 2 preapical teeth. Propodeal spines variable in size but not recurved . . . . . 50

49
return to couplet #48
 * Colour chocolate brown. Larger, HL 1.24-1.35 . . . . . Strumigenys agra


 * Colour yellow. Smaller, HL 0.99-1.17 . . . . . Strumigenys apios

50
return to couplet #48
 * Inner margin of mandible with a translucent lamina that extends from proximal preapical tooth, or close to tooth, to level of anterior clypeal margin. Mandibles in full-face view almost straight and at full closure parallel . . . . . 51


 * Inner margin of mandible without a translucent lamina extending from vicinity of proximal preapical tooth to level of anterior clypeal margin. Mandibles in full-face view with outer margins shallowly convex; rarely almost straight . . . . . 57