In a mature leafcutter colony, ants are divided into castes, based mostly on size, that perform different functions. Acromyrmex and Atta exhibit a high degree of biological polymorphism, four castes being present in established colonies — minims, minors, mediae, and majors. Majors are also known as soldiers or dinergates. Atta ants are more polymorphic than Acromyrmex, meaning comparatively less difference occurs in size from the smallest to largest types of Acromymex.
Leafcutter ant Atta cephalotes
Minims are the smallest workers, and tend to the growing brood or care for the fungus gardens. Head width is less than 1 mm.
Minors are slightly larger than minima workers, and are present in large numbers in and around foraging columns. These ants are the first line of defense and continuously patrol the surrounding terrain and vigorously attack any enemies that threaten the foraging lines. Head width is around 1.8-2.2 mm.
Mediae are the generalized foragers, which cut leaves and bring the leaf fragments back to the nest.
Majors, the largest worker ants, act as soldiers, defending the nest from intruders, although recent evidence indicates majors participate in other activities, such as clearing the main foraging trails of large debris and carrying bulky items back to the nest. The largest soldiers (Atta laevigata) may have total body lengths up to 16 mm and head widths of 7 mm.