Carpenter ants are a large, common species often associated with damage to wooden structures, earning them a reputation as recognized household pests. These insects can measure up to half an inch in length, and their presence often signals a potential problem. Because they are frequently discovered inside wood, the incorrect assumption is that wood makes up their diet. Understanding what these pests actually consume is the first step in managing an infestation.
Primary Food Sources
The diet of carpenter ants is omnivorous, centering on two nutritional components: carbohydrates for energy and protein for growth. Adult worker ants require a steady supply of simple sugars to fuel foraging and nest construction. They collect these carbohydrates from sources such as plant nectars, fruit juices, and honeydew, a sugary excretion produced by sap-sucking insects like aphids.
Protein and fats are needed primarily to feed the developing larvae within the colony, which cannot forage for themselves. Carpenter ants obtain this protein by scavenging dead insects and other arthropods, or by actively preying on smaller creatures.
Workers store the food they find in a specialized stomach, or crop, to transport it back to the nest. Once in the colony, food is shared through trophallaxis, where one ant regurgitates liquid food for others, including the queen and larvae. This efficient sharing system ensures the entire colony, particularly the non-foraging brood, receives the necessary balance of sugars and proteins.
Wood Excavation vs. Consumption
Despite their name and their habit of tunneling through lumber, carpenter ants do not actually consume wood for nutrition. Unlike termites, which possess specialized microorganisms in their gut to digest cellulose, carpenter ants lack the biological mechanism to break down wood fibers. They are physically incapable of deriving any sustenance from the material they tunnel through.
The damage they cause is a result of their need to excavate wood to create galleries and tunnels for their nests, which serve as living quarters for the colony. They meticulously carve out these smooth, polished chambers and push the resulting wood particles, known as frass, out of the nest. They prefer to excavate wood that is already soft, such as decaying, moist, or water-damaged lumber, because it is easier to chew through.
The presence of frass—a mix of wood shavings and dead insect parts—is a sign of nesting activity, not feeding habits. This distinction means that eliminating the colony requires finding the nest location rather than focusing on removing a food source.
Indoor and Outdoor Foraging
Carpenter ants are opportunistic foragers that search for required sugars and proteins in both indoor and outdoor locations. Outdoors, they are frequently found near aphid colonies, where they “milk” the insects for honeydew, or near tree wounds to access sap. They also hunt or scavenge for dead insects and other arthropods on the ground or in decaying organic matter.
When they enter a structure, they seek the same nutritional balance they find in nature, but from household sources. Indoor foraging often targets the kitchen, where they are attracted to sugary spills like syrup, honey, or fruit juices. Protein sources in the home, such as pet food, small scraps of meat, or grease residue, are strong attractants, particularly for the developing brood.
Foraging activity is most intense between sunset and midnight, with workers traveling up to 100 yards from the nest. By tracking the trails of ants moving between the structure and food sources, homeowners can determine if the ants are temporary visitors or if they have established a satellite nest inside the building. Eliminating accessible food sources is a step in prevention and control.