South America is identified as the home of the best-known fungus-farming ants, the parasol ants. Their colonies make the region a concrete example in the book’s account of cultivation as an evolved biological partnership: ants gather and prepare leaves for fungi, then harvest the crop that feeds the colony and its brood.

Fungus gardens underground

Parasol ants cultivate a particular species of fungus in compost beds made from chewed leaf fragments. Their nests are immense underground networks of passages and galleries, extending to depths of ten feet or more. Some have been excavated from as much as 40 tons of soil, and single colonies numbering more than two million individuals have been found. The scale of these nests makes cultivation not a marginal behavior but an organizing feature of colony life. The workers forage for leaves not to eat them directly, but to turn them into compost for the fungus gardens. The colony’s demand for foliage is gargantuan, and parasol ants can consequently be a major economic pest. What the workers harvest, however, is fungus: they eat it and feed it to their brood. The crop converts leaf material into food more efficiently than the ants’ own stomachs could.

A partnership with distinct interests

The ants’ cultivation also tends the crop. Workers weed the gardens, removing alien fungi that would compete with the ants’ domestic species. The fungus may benefit in turn: the ants could propagate it more efficiently than it could disperse its own spores. The book therefore presents the arrangement as a possible form of mutual altruism, while keeping the claim appropriately qualified: the fungus’s benefit is proposed rather than established as a measured outcome. The South American example belongs to a broader comparison. A very similar system of fungus farming evolved independently among termites in Africa, showing that cultivation is not unique to parasol ants or to one lineage. The parallel makes the ant gardens evidence for a recurring evolutionary solution, rather than an isolated curiosity.

Significance in the argument

The fungus gardens illustrate how cooperation can arise without a general concern for the welfare of another species. The ants gain a food source suited to their needs; the fungi may gain cultivation and protection from competitors. The relationship can thus be described as mutually beneficial while remaining grounded in the different consequences it has for each participant. South America’s parasol-ant colonies give this argument a striking physical form: a vast subterranean agricultural system built around leaves that become compost, and fungi that become food.