Acromyrmex octospinosus
Lateral view of thorax / mesosoma, adult worker. Promesonotum is armed with at least three pairs of spines and teeth. Usually the anterior pairs are large and robust, while the posterior pair is smaller. Separates Acromyrmex from Atta.
Anoplolepis gracilipes
Anterior view of antennal scape, adult worker. The antennal scapes are extremely long, their length measuring more than 1.5x the length of the head. Used in Antkey to separate Anoplolepis gracilipes and Paratrechina longicornis from other formicine genera.
Atta cephalotes
Lateral view of pronotum, adult worker. The pronotal spines are strongly arching anteriorly. This character may be informative for separating Atta cephalotes from Atta sexdens, but attine pronotal spines show considerable infraspecific variation and this character may well prove unreliable, and thus must be used with caution.