cephalic spines
no small teeth anterior to spines

The head anterior to the posterolateral spines is smooth and not interrupted by a pair of small teeth or blunt angles. Used in Antkey to separate Atta cephalotes from Atta sexdens. This is a variable character, and should be used with caution until its usefulness is confirmed.
small teeth anterior to spines

The head has a pair of small teeth or blunt angles anterior to the posterolateral spines. Used in Antkey to separate Atta sexdens from Atta cephalotes. This is a variable character, and should be used with caution until its usefulness is confirmed.
posterolateral corners armed

The posterolateral corners of the head are armed with distinct posteriorly projecting spines. Used in Antkey to separate Acromyrmex and Atta from all other myrmicine genera.
posterolateral corners unarmed

The posterolateral corners of the head are unarmed and lack distinct posteriorly projecting spines. Used in Antkey to separate all other myrmicine genera from Acromyrmex and Atta.