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Carpenter Ants

Credit: Tom Myers


Workers are large (1/8-1/2”) but vary greatly in size, Queens about (1/2-5/8”) Colors vary from black, red and brownish or black and red. Carpenter ants are 1 noded ants with an evenly rounded thorax. Development time (egg to adult) takes at least 60 days. There is only one wingless queen per colony. Colonies contain up to 3,000 workers when maturity is reached in about 3 to 6 years. Swarmers (winged) are not produced until the colony is at least 2 years old.

Most Carpenter Ants establish their first nests in decaying wood and later expand into solid wood. Inside, nests are located in wood (preferably softened by fungus rot), in insulation, and/ or in wall voids. Outside, nests are typically located in rotting fence posts, stumps, firewood, dead portions of standing trees and under stones or fallen logs. The workers forage up to 300 ft from the nest. Carpenter Ants enter buildings around door and window frames, eaves, plumbing and utility lines and tree branches that come in contact with the building. Some workers are active during the day, but most activity is from dusk until dawn.

The first step is to determine if the ants are merely foraging inside for food or if there is a nest inside. The best indication of an INDOOR NEST is sawdust (FRASS), wood piles containing insect body parts and/or a rustling sound in the walls. Gently tap all exposed wood such as floor joists, sill plates, roof rafters, etc. with a screwdriver and listen for sound changes; nest cavities give a hollow dull ring. Check suspicious areas with a knife blade, a blade will penetrate infested wood very easily. Be sure to inspect crawl spaces, basements and attics. Carpenter Ants have trails they follow throughout a structure and often use electrical wires and pipes.

Once the nest has been located, residual sprays and dust can be used to treat the nest. Dust around all water pipes, under sinks, toilets, dishwashers, etc. Treat around base boards, window frames and door frames with labelled residual insecticide. Outside, be sure tree branches are not touching the building. Wood piles should be off the ground and stored away from the building. Exterior sprays with a residual insecticide should be performed treating around window frames, door frames, cracks in the foundation and where the soil and foundation meet. OUTSIDE, check around buildings for foraging trails, especially in the direction of trees and shrubs, wood piles etc. Spray around foundations and other areas of concern outdoors. Cut trees and shrubs back that come in contact with the building. Caulk around window and door frames and any gaps around electrical and water lines will help to prevent the ant from coming indoors.

Inspect old railway tiles around the building, as often they are the source of infestation. Treat the tiles with insecticide dust or residual sprays.

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