Pogonomyrmex coarctatus-group

Workers of the coarctatus-group are recognized by the following characters: (1) large, sometimes polymorphic, (2) numerous hair-bearing foveae scattered across dorsum of head, (3) most to all of cephalic dorsum with very fine, dense, longitudinal rugae or striae, (4) antennal scapes short, extending less than one-third the distance from posterior margin of eye to vertex, and (5) posterolateral margin of head with a carina that is much coarser than rugae on cephalic dorsum. All of these features also characterize queens, which are known for all four species. Queens are also larger than those of other South American congeners with head widths that range from 2.91-4.06 mm. Males (known for all four species) are diagnosed by: (1) foveae (usually small and inconspicuous) scattered across dorsum of head, more prevalent along posterior margin, and (2) large size (HL > 1.75 mm and ML > 2.90 mm).