Ants do farm, and they have been doing so for millions of years, predating human agriculture by tens of millions of years. This farming involves the sophisticated management of a cultivated food source, demonstrating specialized behavior usually associated only with humans. Certain ant species have evolved complex, organized societies centered entirely around maintaining and harvesting their crops. Their agricultural practices fall into two main categories: the cultivation of fungi and the husbandry of insects.
The Primary Example: Fungus Cultivation
The most advanced form of ant agriculture is the cultivation of fungi, practiced by the Attine ants, a group of over 240 species found exclusively in the Americas. These ants, which include the well-known leafcutters (Atta and Acromyrmex species), do not eat the vegetation they collect. Instead, they use it as a substrate to grow a specific type of fungus, which is the sole food source for the ant larvae and the primary food for adult workers.
The relationship between the ants and their fungal crop is a classic example of mutualistic symbiosis. The ants provide the fungus with prepared plant material, protection, and an ideal growing environment. In return, the fungus produces specialized, nutrient-rich swellings called gongylidia, which the ants harvest and consume. For the most advanced farmers, the fungus has become completely domesticated and cannot survive outside the ant nest, while the ants cannot survive without the fungus.
The raw materials used to feed the fungal garden vary depending on the ant species. Leafcutter ants cut and carry fresh leaves back to the nest, while “lower attine” species use detritus, dead plant matter, insect feces, or seeds. When a new colony is founded, the queen carries a small pellet of the fungus from her parent colony. This vertical transmission of the crop guarantees the continuity of their specialized food source.
Cultivation Techniques and Colony Management
Ant farmers employ complex techniques to maintain the health and productivity of their underground gardens. A significant task is preparing the substrate before cultivation. Leafcutter ants chew the collected plant material into a pulp, which they treat with glandular secretions to enhance its suitability for fungal growth.
Weeding and pest control are continuous activities within the fungus garden to maintain a clean monoculture. Worker ants constantly remove foreign molds, competing fungi, or infected sections of the crop. They employ a defense strategy involving a symbiotic bacterium, Pseudonocardia, which lives on the ant’s body and produces antibiotics to inhibit the growth of fungal parasites like Escovopsis.
The ants also act as environmental engineers, controlling the nest’s microclimate to optimize fungal growth. Leafcutter ant species maintain their fungus gardens at a constant temperature of approximately 25 degrees Celsius (77 degrees Fahrenheit), with very high humidity levels. They achieve this climate control by selectively opening and closing ventilation tunnels throughout the nest, which can extend several meters underground, regulating airflow and insulation.
Beyond Fungus: The Practice of Ant Dairying
Ant agriculture extends beyond fungi to include a form of livestock husbandry known as “ant dairying” or trophobiosis. This involves managing colonies of certain insects for their sugary secretions, primarily aphids and scale insects. These insects feed on plant sap and excrete a carbohydrate-rich liquid called honeydew, which the ants consume as a high-energy food source.
The ants treat the aphids as domesticated livestock, actively protecting them from predators such as ladybugs and parasitic wasps. They often herd the aphids to the newest, most nutrient-rich parts of a plant to maximize honeydew production. To stimulate the release of the sugary droplet, an ant will gently stroke the aphid’s abdomen with its antennae, a behavior described as “milking.”
In some species, the ants transport aphid eggs into the nest for the winter, rearing them until conditions are suitable for placing them back on host plants. Certain ants may even clip the wings of their aphids to prevent the herd from dispersing, ensuring the sugar supply remains constant.
Ecological and Evolutionary Impact
The development of agriculture in ants, which arose around 60 million years ago, represents a major evolutionary breakthrough. The transition to farming led to intense specialization and a co-dependence known as obligate mutualism. This interdependence means the survival of the ant colony is inextricably linked to the survival of its crop.
This reliable food source allowed farming ant species to achieve massive colony sizes and complex social structures, far surpassing their hunter-gatherer relatives. Leafcutter ants, for instance, have become the dominant herbivores in the Neotropics, collectively harvesting more vegetation than any other single group of animals. Their immense subterranean nests, containing millions of workers and hundreds of fungus chambers, drastically alter the soil and nutrient cycling of their local ecosystems, cementing their role as ecological engineers.
The success of these agricultural systems highlights how a stable, cultivated food supply drives the development of complex societies. The ants’ ability to domesticate both a fungus and other insects demonstrates multiple independent origins of farming behavior, offering a unique parallel to human agricultural history.