Carpenter ants are social insects which form large colonies. A mature carpenter ant colony may contain up to 3,000 individuals, but usually only one queen. Carpenter ants form nests in wood by tunneling against the grain. These galleries are free of mud and sawdust.
Coarse sawdust is present below the entrance of an active nest.
Carpenter ants are drawn to areas with high moisture levels. Outdoors, they may be found in rotting wood of tree stumps and roots, and in moist areas such as under roof shingles, gutters, window sills, near chimneys, firewood, or in untreated wood products on or in the soil. Nests in buildings are frequently located in wood associated with current or old roof leaks and leaky pipes. Unlike termites, carpenter ants do not feed on wood products but are economically important because of the damage they cause by forming nests and because of the foods they contaminate. Generally, the ants do not weaken a building structurally.