Pogonomyrmex species groups

The following is based on Johnson, R.A. 2015. A taxonomic revision of South American species of the seed-harvester ant genus Pogonomyrmex (Hymenoptera: Formicidae). Part I. Zootaxa 4029: 1–142. doi:10.11646/zootaxa.4029.1.1

Pogonomyrmex bispinosus-group

 * Pogonomyrmex bispinosus
 * Pogonomyrmex inermis
 * Pogonomyrmex uruguayensis

Workers in the P. bispinosus-group are diagnosed by the following characters: (1) psammophore well-developed, (2) first gastral tergum lacking striae, (3) posterior surface of petiolar node with transverse rugae or rugoreticulate, and (4) dorsum of postpetiole lacking rugae. Queens have: (1) psammophore well-developed, (2) weak transverse, but usually incomplete rugae on dorsum of postpetiole, and (3) short, delicate hairs along the lateral margin of propodeal declivity.

Pogonomyrmex coarctatus-group

 * Pogonomyrmex coarctatus
 * Pogonomyrmex lobatus
 * Pogonomyrmex marcusi
 * Pogonomyrmex micans

Workers in the P. coarctatus-group are diagnosed by the following characters: (1) first gastral tergum lacking striae, (2) large (HW = 1.97–3.99 mm), sometimes polymorphic, (3) numerous small, hair-bearing foveae scattered across cephalic dorsum (best viewed at > 50x magnification), (4) part to all of cephalic dorsum with very fine, dense, longitudinal striae, (5) antennal scapes short, extending less than one-third the distance from posterior margin of eye to posterior corner of head, and (6) posterolateral margin of head with a carina that is much coarser than rugae on cephalic dorsum. All of these characters also diagnose queens, which are larger than those of all South American congeners (HW = 2.91–4.06 mm).

Pogonomyrmex cunicularius group

 * Pogonomyrmex cunicularius
 * Pogonomyrmex pencosensis
 * Pogonomyrmex serpens

Workers in the P. cunicularius-group are diagnosed by the following characters: (1) psammophore poorly-developed, consisting of short to medium-length hairs scattered across ventral side of head, (2) first gastral tergum lacking striae, (3) head elongate (CI < 90.0), (4) femur long (HFL > 2.05 mm; HFI > 118.0), (5) scapes long, surpassing posterior corners of head; entire scape with pronounced longitudinal striae, (6) eyes small, ranging from 0.15–0.19x HL, and (7) anterior margin of clypeus flat to weakly convex, apron lacking clypeal teeth.

Queens are diagnosed by: (1) ergatoid, with morphology similar to workers except for presence of ocelli and slightly larger size compared to workers, (2) psammophore poorly-developed, consisting of short to medium-length hairs scattered across ventral side of head, (3) first gastral tergum lacking striae, (4) mesosoma weakly to moderately enlarged, mesosomal segments fused, metanotal groove weakly to moderately impressed, (5) head elongate (CI < 94.0), and (6) femur long (HFI > 116.0).

Pogonomyrmex naegelii-group

 * Pogonomyrmex abdominalis
 * Pogonomyrmex naegelii
 * Pogonomyrmex tenuipubens

Workers in the P. naegelii-group are diagnosed by the following characters: (1) first gastral tergum lacking striae or striae restricted to base or rarely extending beyond the base, (2) small (HW = 1.06–1.33 mm), (3) psammphore poorly-developed, consisting of short to medium-length hairs scattered across ventral side of head, (4) superior and inferior propodeal spines well-developed, inferior spines >0.5–1.0x length of superior spines, (5) in profile, ventral process of postpetiole large and bulbous, its height much greater than its length, and (6) concolorous tannish-brown, occasionally with blackish gaster. Queens in the P. naegelii-group are diagnosed by: (1) first gastral tergum lacking striae or with faint to moderately strong longitudinal striae near base that sometimes extend over anterior one-half of tergum, (2) small (HW < 1.30 mm), (3) psammophore poorly-developed, consisting of short to medium-length hairs scattered across ventral side of head, (4) inferior propodeal spines triangular, moderately to well-developed, (5) in profile, ventral process of postpetiole large and bulbous, its height much greater than its length (for only alate queens), (6) concolorous tannish-brown, occasionally with blackish gaster, and (7) anterior margin of clypeus flat.