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Insects and other arthropods

Finding an ant nest

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Inspection of firewood can sometimes reveal an ant colony.
Photo: Insectarium de Montréal (Claude Pilon)

Finding an ant nest is easier said than done, especially if it is located inside the house. However, in most cases, the nest is located outside the house. Here are a few tips for finding it:

  • Observe the ants coming and going. When a foraging worker finds food, it leaves a trail of pheromones along its path to show its counterparts the way between the source of the food and the nest. You’ll see ants following this chemical trail in a single-file line. Following the trail can help you locate the nest. But what can you do if the trails are several metres long, winding through areas you can’t detect or access? Plastic containers containing sweet bait (honey diluted with water, jelly, jam) can be placed along the ants’ chemical trail. Attracted by the bait, the ants will change their path and over time, the ants will use the shortest path between the new food source and the nest. This method is effective for locating the nest’s position in the house. Remember that bait placed further away from the nest is less attractive than bait placed closer to the nest.
  • Check bags and containers of food. You may find ants foraging in them.
  • Remember: Ants are most active at night. A flashlight is handy for following them from their feeding place back to the nest. These insects can enter the home by crawling along phone lines, power lines and tree branches that touch the building. They also travel easily underground and under the floors.
  • Listen: The movement of many carpenter ant legs in a building creates a slight clicking sound. It’s easier to hear the sound with a stethoscope (used as a detection tool). If the surface is struck, the insects’ activity will increase, as ants are sensitive to vibrations.
  • Finding small piles of sawdust is a good indicator of a carpenter ant nest, especially if the piles keep appearing in the same place. These piles of sawdust are generally found at entrances to a nest, which take the form of small holes, cracks and crevices. Look for carpenter ant nests in trees found in a 90-m radius around the house. Try to find piles of sawdust, parts of rotting trees, etc. Check the most humid places in the house: attics, basements, wooden doorframes and windowsills, leaky roofs, gutters, leaky pipes, bathroom and laundry room, outside steps, etc.

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