Leafcutter ants are found in warmer regions of Central and South America. These remarkable social insects have evolved an advanced agricultural system. They feed on a specialized fungus that grows only in the underground chambers of the ants’ nest. The ants actively cultivate their fungus, feeding it with freshly-cut vegetation and maintaining it free from pests and weeds. This is done by a symbiotic relationship with a colony of bacteria that grows on the ants that protect the fungus. The bacteria evolve along with the mold that would feed on the fungus – essentially the ants have their own portable antibiotics.
Leafcutter ants comprise 2 genera – Atta and Acromyrmex – with a total of about 50 species, some of which are major agricultural pests. Some Atta species, for example, are capable of defoliating an entire citrus tree in less than 24 hours.
A mature leafcutter colony can contain more than 2 million ants, mostly sterile female workers. They are divided into castes, based mostly on size, that perform different functions involving gathering leaves outside the nest, turning plant material into paste for the fungus to digest, and harvesting the fungus for others to eat. Some are soldiers who defend the nest from intruders.