Ants are one of the most successful insect groups globally, thriving in nearly every terrestrial ecosystem. Their success is tied to a highly flexible and varied diet, determined by the species, colony caste, and immediate environment. The feeding habits of the Formicidae family are complex, ranging from simple foraging to sophisticated agriculture and animal husbandry. This collective approach allows them to exploit a vast array of food sources, ensuring the continuous growth and survival of the colony.
The Core Diet: Sugars and Proteins
The generalist ant diet is fundamentally bipartite, separating the colony’s nutritional needs into two primary categories: immediate energy and growth material. Carbohydrates, typically in the form of simple sugars, serve as the primary fuel source for the adult worker ants. These sugars are acquired from plant secretions such as nectar, fruit juices, and extrafloral nectaries, which are specialized glands on plants that produce sweet liquid.
A major sugar source is honeydew, a sticky, sugary liquid excreted by sap-feeding insects like aphids and scale insects. Honeydew is rich in glucose, fructose, and complex sugars, providing a dense, easily transportable energy packet for the foraging workers.
Proteins and fats form the building blocks necessary for colony development and are sourced from other arthropods. Adult workers hunt live prey or scavenge dead insects and other animal remains to acquire the amino acids and lipids needed for tissue growth. This protein-rich food is provisioned to the larvae and the queen, not the adult workers, who have a low protein requirement. Larvae require protein for rapid growth, and the queen needs it for the continuous production of eggs.
Specialized and Cultivated Foods
Beyond general scavenging, many ant species have evolved highly specialized diets that involve complex cultivation practices. The leafcutter ants (genera Atta and Acromyrmex) are renowned for their sophisticated agriculture. These ants do not eat the leaves they harvest; instead, they use the vegetation as a substrate to cultivate a specific, domesticated fungus.
The harvested leaves are processed into a pulp that acts as fertilizer for the fungus, which grows specialized, nutrient-rich swellings called gongylidia that the ants consume. This symbiotic relationship is protected by the ants, who actively weed out parasitic molds and use antimicrobial secretions to maintain the purity of their fungal garden.
Harvester ants (genus Pogonomyrmex) have adopted a granivorous diet, relying almost entirely on seeds. These ants possess specialized, powerful mandibles for cutting and processing seeds, which they collect and transport back to the nest. The seeds are stored in underground chambers known as granaries, which can contain hundreds of thousands of seeds to sustain the colony through lean seasons.
Some ant species engage in a form of animal husbandry known as myrmecophily, an advanced stage of honeydew collection. This involves ‘herding’ aphids or scale insects, protecting them from predators, and transporting them to the most succulent parts of a plant to maximize sap intake. Some ant species will carry aphid eggs into the nest over winter and place the newly hatched aphids back onto host plants in the spring. This behavior ensures a reliable supply of the sugary honeydew, which the ants harvest by stroking the aphid with their antennae to stimulate excretion.
The Role of Liquid Food Sharing
The physical act of feeding in an ant colony is a highly social process called trophallaxis, the direct, mouth-to-mouth transfer of liquid food between individuals. When a forager returns to the nest with liquid food, such as nectar or honeydew, it stores this in a specialized foregut organ called the crop, often referred to as the “social stomach.” This food is held in reserve for the colony rather than being immediately digested.
Through trophallaxis, the forager regurgitates a droplet of this liquid to nestmates, who then share it with other workers, the queen, and the larvae. This mechanism is not simply a nutritional exchange; it is a communication system that distributes regulatory molecules, such as proteins and hormones, throughout the colony. By sharing the liquid, the ants create a unified nutritional and physiological state, ensuring that resources and chemical signals are rapidly distributed to maintain colony cohesion and regulate development.