Acromyrmex echinatior

Acromyrmex echinatior is a species of New World ants of the subfamily Myrmicinae of the genus Acromyrmex. It is found in the wild naturally from Mexico to Panama.

Overview
Commonly known as "leaf-cutter ants" they are a species of ant from one of the two genera of advanced attines within the tribe Attini.

Acromyrmex can be identified from the closely related Atta genus of leafcutter ants since they have 4 pairs of spines and a rough exoskeleton on the upper surface of the thorax.

A mature Acromyrmex echinatior colony contains mostly sterile female workers. They are divided into castes, based mostly on size, that perform different functions. Acromyrmex exhibit a high degree of biological polymorphism, four castes being present in established colonies - minims (or "garden ants"), minors, mediae and majors. Majors are also known as soldiers or dinergates. Each caste has a specific function within the colony. Acromyrmex ants are less polymorphic than the other genera of leafcutter ants Atta, meaning that there is comparatively less differential in size from the smallest to largest types of Acromymex. The high degree of polymorphism in this genus is also suggestive of its high degree of advancement. There is a genetic component to worker caste polymorphism in A. echinatior with their paternal genes producing significant variation in the propensities of workers to develop into minors and mediae.

Like Atta, Acromyrmex subsists mostly on a particular species of fungus (genus Leucocoprinus) which it cultivates on a medium of masticated leaf tissue. This is the sole food of the queen and other colony members that remain in the nest. The media workers also gain subsistence from plant sap they ingest whilst physically cutting out sections of leaf from a variety of plants.

Before leaving their parent colonies, winged females take a small section of fungus into their bucchal pouches and it is with this that the subsequently wingless queens 'seed' the fungus gardens of incipient colonies, cutting and collecting the first few sections of leaf themselves.

Acromyrmex has evolved to change foodplant constantly, preventing a colony from completely stripping off leaves and thereby killing trees, thus avoiding negative biological feedback on account of their sheer numbers. However, this does not diminish the huge quantities of foliage they harvest.

In Costa Rica this species prefers open dry habitats such as urban areas around San Jose and seasonally dry habitats of Guanacaste Province. There is evidence to suggest that this species nests may occasionally be arboreal.

Queens multiply mate, and colonies are facultatively polygynous. Nonreproductive workers of the colony 'police', that is, selectively destroy worker-laid eggs, but don't attack reproductive workers. Relatedness incentives are the most likely ultimate cause of the evolutionary maintenance of worker–egg policing in A. echinatior.