Attine ants, like humans, are accomplished farmers. Most advanced are the leafcutter ants, a group of species found mostly in South and Central America. They depend for their livelihood on cultivating fungus gardens. Worker ants cut off pieces of leaves, which are then chewed on by progressively smaller ants until the leaf goo is ready to serve as substrate for the fungus gardens. The ants and the fungi have coevolved to the point where neither can survive without the other. The ants bring biomatter to serve the fungus nutrients, and then collect particularly nutritious “fruits”, called gongylidia, which are then fed to young ants. Also part of this symbiotic relationship are bacteria that live on the ants and serve as antibiotics, protecting the fungus gardens from parasites. Leafcutter societies are highly complex and can consist of as many as ten million workers, serving a variety of roles like foragers, soldiers, gardeners and garbage disposal workers (which, in the cases where the garbage heap is external to the nest, are shunned by the other ants).
Through DNA analyses and by studying extant ant species, scientists have found that ant agriculture evolved a single time, 50 million years ago. By comparison, humans didn’t invent agriculture until roughly ten thousand years ago. Five different kinds of ant agriculture exist, and the latest and most advanced kind practiced by the leafcutters evolved some 8-12 million years ago. Unlike earlier forms of ant agriculture, the fungus cultivated by leafcutter ants is incapable of surviving in the wild, and it is the only ant-cultivated fungus that produces the “fruits” or gongylidia harvested by the ants.
Wherever they live, leafcutter ants are ecologically dominant. Leafcutter ants may cut up to an estimated 17% of the annual leaf production in the areas they inhabit. More about these ants here.