Workers of the genus Cheliomyrmex are unique among the New world army ants (subfamily Ecitoninae) in that their mandibles are armed with elongate, spine-like teeth. We present the first prey records for this genus. Cheliomyrmex andicola prey on large-bodied ground dwelling invertebrates and, possibly, on vertebrates. Unlike other army ants, C. andicola workers use their sting during prey capture. The workers' unusual mandibles and potent stings may be adapted for piercing and gripping the integument of nonarthropod prey animals, and for rapidly subduing large-bodied prey, respectively. The genus Cheliomyrmex may be the sister taxon to other Neotropical army ants (Ecitoninae), and Cheliomyrmex shares features of mandibular morphology and prey selection with Old World driver ants in the genus Dorylus. Mass cooperative foraging, an important element of army ant behavior, may have arisen in part as an adaptation for exploiting large-bodied prey.