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Insects and other arthropods

Why do we have ants in the house?

Ants nest in damp or rotting wood. They do not attack sound wood. They can, however, cut a damp gallery within dry wood.
Photo: Service canadien des forêts (Thérèse Arcand)
Camponotus sp, Québec, Canada.
  • Camponotus sp, Québec, Canada.
  • Monomorium pharaonis, Québec, Canada.

There is no need to worry about ants in the home, as these insects pose no threat to health. However, because ants can get into the tiniest crevices to find food, they can be quite a nuisance in the pantry. The best thing to do is tolerate them while taking steps to remedy the situation.

Are ants active in winter or spring?

In nature, ants spend the winter buried deep in the ground. They emerge in the springtime and resume their activities.

However, if you find them in the house:

  • During the winter: The nest and queen are inside the house or very close to its foundation. The ants are looking for food and water.
  • Only in spring and summer: The nest and queen are outside the house. The ants are only coming inside to look for food and do not want to move inside. In the springtime, ants are also drawn to warmth as they wait for temperatures to rise outdoors.

Possible causes of an ant infestation

  • A young queen has been introduced into the house through a crack or travelled indoors on heating wood, boxes and other objects brought into the house.
  • Satellite nests have formed, with or without the queen. Pharaoh ants frequently migrate from one dwelling to another.

Infestation or impromptu visit?

Are there ants crawling across the floor upstairs? Ants crawling in a single-file line along the kitchen walls or floor? How did they get there? Should you be concerned about them?

  • A few isolated ants exploring a room, counter or windowsill. They are usually foraging worker ants. Less frequently, it is a queen looking for a shelter to found her colony. Kill any ants you see and be vigilant in order to keep them from spreading.
  • A large number of ants are in one area continuously. You can try to control the infestation or call a professional exterminator.
  • Winged ants are coming out of cracks in the walls or ceiling. They then try to escape through the windows. Generally, the presence of winged adults is an indicator that there is a fully established colony of ants somewhere inside the house or near the foundations. In Quebec, carpenter ants are the only ants that harbour winged adults over the winter. In other species, the adults leave the colony in the summer.

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