Carpenter Ant

Among the largest of ants, 1/4- to 3/8-inch long. Color varies depending on species, from red to black or a combination. The most common species is black.


Carpenter ants get their name because they excavate wood in order to build their nests, leaving hollowed-out tunnels. These colonies require a constant source of water to survive, and are often found in wet, decayed wood such as dead limbs and tree stumps.

Inside, they can be found in wet, poorly ventilated spaces such as crawl spaces or attics. While carpenter ants don’t eat wood, their excavations pose a property threat, making ant control imperative. In the spring, winged reproductive ants called swarmers fly out to start new colonies.

Colonies can contain up to 50,000 workers.


Will feed on nearly anything people eat, particularly sweets and meats. The favorite food of adult carpenter ants is the sweet “honeydew” produced by plant-feeding insects, such as aphids, scales, and mealybugs. Carpenter ants also feed on other insects.


Successful carpenter ant control depends on eliminating the parent colony, which is usually located outdoors. Finding and treating as many nests (satellite colonies) as possible is the key to carpenter ant control.

EUI recommends removing stumps, logs, and waste wood within 100 yards of the building. Do not allow vegetation, especially evergreen shrubs and trees, to be in contact with the house. We also suggest storing firewood away from the house and off of the ground, and bring it into the house only when needed. It is important to keep wooden parts of the house and other structures dry by making necessary repairs to roofs, flashing, gutters, and downspouts. EUI also suggests replacing any water-damaged, decaying wood. Usually, carpenter ants will not infest wood that is sound and has moisture content of less than 15 percent. Keep exterior wood surfaces painted and sealed. Seal holes through which pipes and wires enter the house. Use pressure-treated wood for parts of the structure that will be in contact with the soil. Place a moisture barrier over soil in crawl spaces and under wooden porches, and provide adequate ventilation for such spaces.

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