Carpenter ants bite when their nests are disturbed. Biting is a defense mechanism for the carpenter ant, which uses its strong wood-cutting mandible to ward off any potential intruders.
Because the carpenter ant is a large ant, it has a powerful bite that can break the skin and that can be quite painful. The pain is increased by the release of formic acid during the bite. Formic acid is a defensive chemical that the carpenter ant sprays into the wound and is the same type of acid found in a bee sting. The sting of a carpenter ant can cause a prolonged sensation of burning although it is not venomous.