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Carpenter ant

Carpenter ant -
  • Latin name: Camponotus sp.
  • French name: Fourmi charpentière
  • Order: Hymenoptera
  • Family: Formicidae




Damage, symptoms and biology

Ants are found in every natural setting; among the most destructive of them are the carpenter ants. They are the most efficient wood-destroying insects in North America and are the largest of our common ants. Outdoors they generally live in colonies, extensively honeycombing the wood in old trees or stumps in which rot is present. In their natural habitats in forests, they are important decomposers of decaying trees. However, they often make their nest in damp woodwork in buildings and their tunnelling weakens structural members.

The most commonly encountered carpenter ant is the black carpenter ant, Camponotus pennsylvanicus. They do not eat wood, but remove it to produce galleries that serve as their nests. The natural food of the black carpenter ant consists mostly of dead and live insects, honeydew, sap, juices of overripe fruit, and refuse. It will also feed on household foods such as sweets, raw and cooked meats, and fruits.

Most adult carpenter ants are black but some may be reddish brown to yellowish. The young are grub like and must be cared for by other colony members. Overwintering males and females in colonies over 3 years old take part in nuptial flights that occur from May to late July. Fertilized females then establish nests. The first brood of workers are raised to maturity on salivary secretions and are smaller than normal. Subsequent broods are fed by workers and the individuals are larger. Long-established colonies have workers of various sizes consisting of a reproductive female or queen, winged males and virgin females.

Live trees are infested occasionally when the ants are able to enter through cracks, scars, knotholes, and decaying areas. Once inside the wood they remove the faulty part and often extend their galleries into adjacent sound wood. Infested trees are subject to wind breakage and the wood is usually useless for lumber or pulpwood.

Houses are often invaded by carpenter ants coming from nearby nests. The most commonly damaged parts include support timbers, porch pillars, sills, girders, joists, studs, window casings, and external trim. Their presence in wood is usually indicated by the piles of wood particles ejected from their tunnels. You can look for these piles of wood particles if you suspect that carpenter ants are nesting in your home. Then use a hammer to sound the suspect wood for the presence of the nest. The wood will sound hollow if a nest is present.

Other information

Establishment of colonies of carpenter ants in wooden structures can generally be prevented if the wood is dry and free from rot. The use of kiln-dried wood or wood preservatives will prevent rot. As a general rule of thumb, to keep any insect out of your home, make your house insect proof by caulking around doors and windows and fill or plug any cracks or crevices in your home that may be leading from the outside to the inside. Ensure that infested wood is not brought into the home; cutting back tree branches in contact with the house will also help in preventing infestations.

If a carpenter ant nest has been located in your home, you may be able to remove the piece of wood that has the nest in it. This is the most effective and environmentally safe way of ridding yourself of carpenter ants.

If you cannot remove the wood for one reason or another, the next best thing to do is to drill holes into the nest area and inject an insecticide that is registered for use to control carpenter ants. Inject the insecticide into the nest by the use of an eyedropper. A registered insecticide for use to control carpenter ants can also be placed on ant runways, on window sills and under doorways where they often enter.

REMEMBER: Insecticides, by their very nature, are designed to control insects. Because of this, persons using insecticides must ensure they use them correctly. Always read the product label prior to using the product. Ensure that the product is registered for the target insect and follow label specifications for mixing, application rates, disposal and safety precautions.

Canadian Forest Service Publications

Carpenter ant

Information on host(s)

All woods

Main host(s)

Conifer, deciduous