[3] Revision within the genus by Wagner et al. in 2017 recognized a complex of 10 cryptic species, 3 of which were raised from subspecies classifications and 2 of which were newly described.

This revision also elevated the pavement ant introduced to North America as the species T. immigrans rather than the previous designation as a subspecies of T. caespitum.

These 10 species in the T. caespitum complex are as follows:[4] Workers of most species have a ridged clypeus, an appendaged stinger, mandibles with 3 or 4 teeth, and antennae with 11 or 12 segments or with 3-segmented clubs on the tips.

One species of pavement ant, T. immigrans, is native to Europe and was probably introduced to North America starting in the 18th century.

[5][4] Most known species nest in the soil, in decaying wood, or in leaf litter.