Wood ants are omnivores whose diet centers on two main food sources: honeydew from aphids and invertebrate prey. Honeydew, a sugary liquid produced by sap-feeding insects, makes up roughly 62% of their diet. Insect prey accounts for about 33%, with tree resin, fungi, seeds, and scavenged remains filling in the rest. This balance of sugar and protein fuels both the adult workers and the growing larvae inside their large mound nests.
Honeydew: The Primary Food Source
The single biggest item on a wood ant’s menu is honeydew, a sweet excretion produced by aphids and related insects that feed on plant sap. Honeydew is rich in carbohydrates, amino acids, and water, making it an efficient energy source for active foragers. Wood ants don’t just stumble across honeydew. They actively tend colonies of aphids on nearby trees, protecting them from predators and parasites in exchange for a steady supply of the sugary liquid. This relationship is so reliable that some researchers have compared it to farming.
Wood ants in the genus Formica tend aphids on a variety of tree species. Red wood ants (Formica rufa) commonly tend aphids on sycamore maples, while the Scottish wood ant (Formica aquilonia) tends aphids on Scots pine, birch, and willow. The ants stroke the aphids with their antennae to encourage them to release droplets of honeydew, then carry it back to the nest in their crops (a second stomach used for liquid transport). Some aphid species actually change the composition of their honeydew when ants are present, increasing the concentration of amino acids at the cost of their own growth, essentially offering a richer product to keep their protectors around.
A single large wood ant colony can collect staggering quantities. One widely cited estimate puts annual honeydew intake at up to 500 kilograms per colony, though that figure has been debated among researchers. Even conservative estimates make it clear that honeydew is the caloric backbone of colony life, providing the carbohydrate fuel that keeps hundreds of thousands of workers active through the foraging season.
Insect Prey and Protein
While honeydew covers the energy bill, wood ants also need protein, and they get it by hunting other invertebrates. A study tracking over 11,000 food items carried back to wood ant nests found that caterpillars (moths and butterflies) were the most common prey at 21.2% of all insect items, followed by flies at 17.6%, beetles at 14.9%, and other ants and wasps at 14.5%. The remaining roughly 32% was a mix of other arthropods including spiders and various small insects.
Wood ants are aggressive, cooperative hunters. Workers patrol the forest floor and tree trunks in large numbers, overwhelming prey with sheer force. A single caterpillar might be subdued by dozens of ants spraying formic acid and biting simultaneously. This predatory behavior is one reason foresters have historically valued wood ants: a large colony can consume enormous numbers of leaf-eating caterpillars, helping to protect trees from defoliation.
Not all of this protein comes from live kills. Wood ants are opportunistic scavengers and will readily carry dead insects back to the nest. Any arthropod carcass found within foraging range is fair game.
Why Adults and Larvae Eat Differently
Inside the nest, food gets distributed based on who needs what. Adult worker ants run primarily on carbohydrates. Their bodies are fully developed, and they need quick energy for foraging, nest building, and defense. Honeydew covers this perfectly.
Larvae, on the other hand, are growing rapidly and building new tissue. They need protein. The insect prey that workers drag back to the nest is largely destined for the brood, broken down and fed to developing larvae. The queen also requires protein to produce eggs. Research on ant colonies generally confirms that protein-rich diets are essential for brood development and egg production, but that too much protein actually increases mortality in adult workers. This creates a natural division: the colony channels sugars to the adults and protein to the young.
Tree Resin, Seeds, and Fungi
About 5% of the wood ant diet consists of tree resin, which ants collect from conifers and other trees. Resin serves a dual purpose. It has some nutritional value, but wood ants also incorporate it into their nest mounds, where its antimicrobial properties help suppress fungi and bacteria that could harm the colony.
Wood ants will also collect seeds, particularly those with fleshy, nutrient-rich appendages called elaiosomes that certain plants produce specifically to attract ants. The ants carry the seeds back to the nest, eat the elaiosome, and discard the seed, effectively planting it. This relationship, called myrmecochory, benefits both the plant and the ant. Fungi and other organic material found on the forest floor round out the diet in small quantities, especially when primary food sources are less available.
How Diet Shifts With the Seasons
Wood ant food preferences aren’t static throughout the year. In spring and summer, when colonies are actively growing and raising brood, food collection ramps up dramatically. Summer colonies collect significantly more food overall and show a strong preference for carbohydrate-rich sources, loading up on honeydew to fuel intense foraging activity. They also collect more protein during this period to feed the large numbers of developing larvae.
As autumn approaches and brood production slows, food collection drops. Fall colonies collect less food across the board and show less of the compensatory behavior seen in summer. For example, summer ants offered only protein-heavy food will eat more of it to try to balance their nutrient intake, while fall ants simply eat less. This seasonal shift reflects a strategy of building up reserves when food is abundant and conserving energy as winter approaches. Once temperatures drop enough, the colony enters a dormant period and stops foraging entirely until the following spring.
How Far They Travel for Food
Wood ants forage along well-established trail networks that radiate outward from their mound. These trails can extend 35 meters or more from the nest, with workers traveling up and down specific trees to tend aphid colonies or hunt prey. Trails are maintained by chemical signals (pheromones) and can persist for years, with the same routes used across generations of workers. A large colony with multiple connected mounds can effectively patrol a significant area of forest floor and canopy, making wood ants one of the dominant invertebrate predators in the ecosystems they inhabit.
Foraging is a collective effort involving thousands of workers at any given time. Scouts locate new food sources and recruit nestmates through pheromone trails and direct contact. The efficiency of this system is part of what allows wood ant colonies, which can contain over 100,000 individuals, to sustain themselves on the patchwork of honeydew, prey, and plant materials available in a temperate forest.