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