Strumigenys alberti group

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Strumigenys alberti group (Bolton 2000)



Worker Diagnosis

Mandibles in full-face view and at full closure triangular to elongate triangular, with serially dentate margins that engage through most or all of their length. In ventral view outer margin of mandible without an inflected prebasal angle. MI 15 - 33.

Dentition. Generally with 5 - 7 larger teeth basally. These arranged as either 7 narrowly triangular to spiniform teeth, or as 5 such teeth followed distally by 2 smaller teeth, or with teeth 2, 4 and 6 (counting from base) low and rounded and teeth 3, 5 and 7 tall narrow and acute. Following these are 4 minute denticles and a slightly enlarged apical tooth, giving a total dental count of 12. [One exception (alberti): basal lamella followed by a long, flat-topped second lamella; distal to this teeth 1, 3 and 5 acute, teeth 2 and 4 lower and broadly rounded; then with 4 minute denticles and a small apical tooth; total dental count 10.]

Basal lamella of mandible a high rounded lobe or a more elongate lower and broadly rounded lobe, generally no higher than the tallest teeth; lamella not visible or partially exposed in full-face view when mandibles fully closed.

Labrum terminates in a pair of digitate to conical narrow lobes.

Clypeus with anterior margin convex, usually broadly and evenly so, but more narrowly rounded anteromedially in some species. Lateral margins of clypeus more or less straight to weakly convex, approximately parallel or diverging posteriorly, rounding evenly into the anterior margin.

Clypeal dorsum with anteriorly directed short spatulate hairs that are decumbent to appressed. Lateral and anterior margins of clypeus in full-face view with a continuous fringe of elongate spatulate to spoon-shaped hairs that project freely beyond the outline of the clypeus; those on lateral margins longer and curved anteriorly, those on anterior margin shorter and directed forward.

Preocular carina broad, conspicuous in full-face view.

Ventrolateral margin of head between eye and mandible forming a blunt angle or weak margination between side and ventre. Postbuccal impression shallow and inconspicuous.

Cuticle of side of head within scrobe densely reticulate-punctate.

Scape short to moderate, SI 60 - 86, slightly to distinctly dorsoventrally flattened, with a sharp thin leading edge.

Leading edge of scape with a row of curved elongate spatulate to spoon-shaped freely projecting hairs, some of which are conspicuously curved toward the base of the scape.

Pronotum not marginate dorsolaterally, the dorsum frequently but not universally with a median longitudinal carina.

Propodeum bidentate to short bispinose, the lamella sometimes a narrow carina but moderately broad in a most species.

Spongiform appendages of waist segments fully developed. Base of first gastral sternite in profile with a distinct pad of dense spongiform tissue.

Pilosity. Pronotal humeral hair present, filiform or flagellate, or looped apically. Apicoscrobal hair present, simple or flagellate. In profile the cephalic dorsum close to the occipital margin with a pair or transverse row of 4 elongate, anteriorly curved standing hairs that are usually distinctly differentiated from any other cephalic pilosity that may be present. Mesonotum with a single pair of long curved filiform or very long flagellate hairs. First gastral tergite with flagellate hairs that may be looped apically. Dorsal (outer) surfaces of middle and hind tibiae with short, apically curved narrowly spatulate hairs that are subdecumbent to appressed.

Sculpture. Dorsum of head behind clypeus reticulate-punctate. Most or all of pleurae and side of propodeum smooth and shining. Disc of postpetiole unsculptured, smooth and shining. Basigastral costulae sharply defined and conspicuous.


The alberti-group contains some of the most widely distributed and most commonly encountered Pyramica species of the Neotropical region. The group is so strikingly similar to the speciose capitata group of the Oriental and Malesian regions that an amalgamation of the two groups is a distinct possibility. The taxonomy of the group was covered in detail by Brown (1953a), so only minimal notes are appended to the species here.