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Bugs - Bug Review - University of Illinois Extension

Carpenter Ant

Most carpenter ants that enter the home are black and can vary in length from 1/4 to 3/4 inch. Unlike termites, all carpenter ants have narrow (or constricted) waists and elbowed (bent) antennae.

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.

cabbageworm

Carpenter ant worker

Habit

Carpenter ants are drawn to areas with high moisture levels. Indoors they are typically seen in bathrooms, basement/sump pump areas, laundry areas, along sweating/leaking pipes and crawl spaces. 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.

Damage

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.

cabbageworm

Carpenter ant damage

Control

Non chemical: Inspect the structure and nearby grounds for nests. Once the problem areas have been identified, areas with high moisture levels should be ventilated or drained. Replace wood damaged by carpenter ants, other insects, or decay organisms.

Keep firewood away from the house and off the ground. Caulk and repair cracks and crevices in the structure. Repair leaky pipes and unclog gutters to prevent rainwater from backing up, and repair chimney flashing.

Chemical: Contact your County Extension office for current pesticide controls.