Strumigenys tetragnatha group

Strumigenys tetragnatha group Bolton (2000)

Species

Afrotropical-West Palaeartic

Worker Diagnosis

Mandibles in full-face view and at full closure stoutly triangular and with massive teeth that engage throughout the visible length; without a basal gap between the mandibles and the anterior clypeal margin. In profile dorsal margin of mandible distal of clypeus strongly arched-down-curved so that much of its length is almost at a right-angle to the long axis of the head. In ventral view outer margin of mandible with a marked prebasal inflected angle. MI 20-27.

Dentition. Immediately distal of the basal lamella are 5 large recurved conical teeth; distal of these are 3 denticles that share a common base, giving a total dental count of 8. Basal lamella of mandible a massive broad-based triangular lobe, its anterior margin visible in front of the clypeal margin in full-face view.

Labrum terminates in a pair of broad blunt flat lobes that diverge anteriorly and are separated by a V-shaped anteromedian impression.

Clypeus with anterior margin concave, its lateral margins divergent posteriorly in full-face view. Outer margins of mandibles intersect the anterior clypeal margin at the blunt clypeal anterolateral angles.

Clypeal dorsum with minute appressed simple hairs, the lateral margins with similar appressed anteriorly directed minute hairs.

Preocular carina not visible in full-face view, concealed by lateral expansion of frontal lobe and frontal carina.

Ventrolateral margin of head sharply marginate in front of eye, the margination slightly concave and terminating anteriorly in a tooth or blunt projecting angle. Postbuccal impression conspicuous; behind it the ventral surface of the head forms a deep convex bulge, then becomes concave and narrow near the occiput. Upper scrobe margins very thick in profile.

Cuticle of side of head within scrobe reticulate-punctate, superficially reticulate or smooth.

Scape very short, SI 41-55, slightly dorsoventrally flattened and with a sharp leading edge that is evenly shallowly convex.

Leading edge of scape hairless or at most with minute appressed hairs that are directed toward the apex of the scape.

Pronotal dorsum transversely flat to shallowly concave and sharply marginate laterally.

Spongiform appendages of waist segments large; ventral spongiform process of petiole deep, curtain-like. Base of first gastral stemite without trace of spongiform tissue.

Pilosity. Pronotal humerus with a simple or flagellate projecting hair; pilosity otherwise variable.

Sculpture. Dorsum of head behind clypeus with fine spaced punctures on a glossy surface medially, denser and dull peripherally; or densely reticulate-punctate. Disc of postpetiole finely longitudinally costulate. Basigastral costulae fine and very dense, extending over half or more of the first gastral tergite and posterior to them the surface densely reticulate or reticulate-punctate.

Notes

The two previously known species of this distinctive group were documented in Bolton (1983); a third species is added here. The three are quickly discriminated by differences in cephalic pilosity and sculpture.

References

Bolton, B. 1983. The Afrotropical dacetine ants (Formicidae). Bulletin of the British Museum (Natural History). Entomology. 46:267-416.
Bolton, B. 2000. The ant tribe Dacetini. Memoirs of the American Entomological Institute. 65:1-1028.