Acromyrmex

Acromyrmex is a genus of New World leafcutter ants in the subfamily Myrmicinae, tribe Attini. Along with the closely related Atta, Acromyrmex species are known for their sophisticated fungus-farming behavior. They are native to the Americas, from the southern United States through Central America and much of South America, inhabiting forests, grasslands, and disturbed areas. Nests are typically built underground with foraging trails and above-ground entrance holes.

Ecology and social structure: Acromyrmex ants are eusocial, forming colonies that include a reproductive queen and a worker caste with several subgroups, including minor workers, major workers, and soldiers. They forage for vegetation, cut fresh leaves, and transport them back to the nest to feed a fungal cultivar. The primary cultivar is a basidiomycete, commonly Leucoagaricus gongylophorus, which produces nutritionally rich structures consumed by the ants. The ants’ diet thus revolves around the fungus, rather than the leaves themselves. The genus exhibits clear caste differentiation and coordinated collective tunneling and foraging behavior.

Nesting, defense, and symbiosis: Within the nest, the fungus garden is maintained in specialized chambers, while a refuse area and nest protection zones help manage waste and deter pathogens. The ants host diverse microbial associates, including antibiotic-producing bacteria, to defend the garden against pathogens such as Escovopsis. Reproduction involves nuptial flights in many species, with queens founding new colonies; some colonies also spread by budding.

Impact and significance: Acromyrmex can become abundant in suitable habitats and may damage crops, pastures, and ornamental plants, making them notable as agricultural pests in some regions. They are important model organisms for studying social insect behavior, symbiosis, and coevolution with cultivated fungi.