 "Acromyrmex" can be distinguished from the closely related leafcutter ant genus "Atta" by having four pairs of spines and a rough exoskeleton on the upper surface of the thorax compared to three pairs of spines and a smooth exoskeleton in "Atta".Much of the inside of the "Acromyrmex" head is occupied by the muscles that close the jaws; the muscles that open the jaws are much smaller.The brain, though tiny, is a very complex organ, and allows "Acromyrmex" to learn and react to its surroundings.