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Carpenter Ants

Behaviour and Biology

If you’re finding big, black ants (some may even have wings) in or around your home, you might have carpenter ants. Carpenter ants are very common in areas where there is an abundance of damp or decaying wood, including old or dead trees, stored firewood, stumps, fence posts, structural posts or beams, decks, window sills, hot tubs and soffits. Some of the tell tale signs of carpenter ants include the “clicking” or “crunching” sounds you might hear inside a wall (similar to the sound you hear when you pour milk on cereal) or sawdust (known as “frass”) that might be around your home or yard. Carpenter ant populations vary from 10 to 20,000 workers, with large colonies having up to 100,000 workers. The workers and swarmers are the ants you are most likely to see as they leave the nest. What you may not be seeing are the eggs, larvae, pupae and the queen that stay in the nest(s).


Carpenter ants can cause serious damage to the structure of your home. They chew up wood, but unlike termites, do not digest it. Instead, they spit the chewed up wood back out, which would explain the sawdust or frass piles you might be finding.  They borough into wood to create tunnels, or “galleries”, which would be a part of the ant colony’s nest(s).  The wood they’re attacking may weaken the structural integrity of your home, fence or trees adjacent to your home. If left long enough, these ants will cause severe damage and pose a structural risk to any building they are in.

Carpenter ant damage

Carpenter Ants can cause serious structural damage


Ant Control Strategies


The key to controlling carpenter ants is to determine where the main nest and, if applicable, the satellite nests are. Nests can be inside the home, or out in the yard. Once identified, carpenter ant nests can be treated with an appropriately labeled insecticide. If the nest is outdoors, be aware that your municipality may have a by-law that prevents the application of certain insecticides, so it’s important to research whether treatment is permitted or not. If there are nests inside the home; location specific, crack and crevice insecticide applications are necessary, and may even involve drilling access holes into wall voids. Given the complexity in determining where nest(s) are (both inside and outside); the type of insecticide formulation (i.e. dust, emulsifiable concentrate, aerosol, granular or bait) to use and the availability of these products to the unlicensed applicator, we recommend seeking the help of a professional to solve any carpenter ant problems you might be experiencing.