Key Takeaways
- Health Canada says carpenter ants are from 6 to 25 mm long.Source: Health Canada, Carpenter ants (Pest control tips) (June 2013)
- Natural Resources Canada says males and females from carpenter ant colonies over 3 years old take part in mating flights from May to late July.Source: Natural Resources Canada, Carpenter ant (insect factsheet) (October 2011)
- Health Canada says carpenter ants live in large colonies with hundreds of workers.Source: Health Canada, Carpenter ants (Pest control tips) (June 2013)
- Ontario's average spring temperature rose 1.5°C between 1948 and 2016, and its annual average rose 1.3°C.Source: Environment and Climate Change Canada, Canada's Changing Climate Report, Chapter 4: Changes in Temperature and Precipitation Across Canada (2019)
- Across Canada, the frost-free season grew by 20 days between 1948 and 2016, starting about 10 days earlier.Source: Environment and Climate Change Canada, Canada's Changing Climate Report, Chapter 4: Changes in Temperature and Precipitation Across Canada (2019)
- Canada's growing season, which starts after six days in a row averaging above 5°C, got about 15 days longer between 1948 and 2016.Source: Environment and Climate Change Canada, Canada's Changing Climate Report, Chapter 4: Changes in Temperature and Precipitation Across Canada (2019)
Do carpenter ants eat wood like termites do?
No. Unlike termites, carpenter ants don't eat wood: they burrow into it to nest and throw the wood out as sawdust-like shavings. Natural Resources Canada calls carpenter ants the largest of our common ants, and a lot of people get them wrong. When you're looking at the damage, the difference from termites doesn't matter much, but it matters a lot for how you treat them.
Are Ontario springs getting warmer and starting earlier?
Yes: Ontario's average spring temperature rose 1.5°C between 1948 and 2016, and across Canada the frost-free season grew by 20 days, starting about 10 days earlier. Both figures come from Canada's Changing Climate Report, which also found Ontario's annual average rose 1.3°C over the same period.
The same report says Canada's growing season, which starts after six days in a row averaging above 5°C, got about 15 days longer between 1948 and 2016.
Where do carpenter ants nest: outside or inside the house?
Both: outdoors they are found in dead trees, stumps and logs, and part of a colony sometimes moves into a nearby building to set up a smaller satellite colony there. Health Canada, which describes both, also lists spots under fallen logs and stones outdoors, and notes some experts believe this move into buildings is the main way carpenter ants invade houses.
Health Canada says carpenter ants get into houses through windows, holes in foundations, heating ducts and air conditioners, power or telephone cables, branches touching the house, attached porches and sheds, and firewood brought inside. They go for wet wood first, so a slow leak under a sink or around roof flashing gives them exactly what they want.
How do you get rid of carpenter ants in your house?
Find the main nest outside where possible, treat every active tunnel and trail inside, seal the entry points and fix the moisture that drew the ants in. Treating only inside the house rarely keeps them away for long. Health Canada says that with a satellite colony, the parent colony should be found and destroyed for the most effective control.
If you're seeing large black ants inside (Health Canada says carpenter ants are 6 to 25 mm long), especially in spring or early summer, get the place checked. One ant in the kitchen may just be a forager from a colony outside. Health Canada says to look for a high concentration of ants in one area, like under the kitchen sink, and for piles of sawdust-like borings and slit-like openings in woodwork.
Sources
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Sting Out Pest Control. (2026, October 17). Carpenter Ants in a Warming Ontario. https://www.stingoutpestcontrol.com/blog/carpenter-ants-warming-ontario
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