Quick facts
- Size
- Workers about 1/4 to 1/2 inch, among the largest ants
- Looks like
- Black or black and red, evenly rounded back
- Peak season
- April through June, swarmers in spring
- Where in Michigan
- Statewide, very common in wooded areas and northern cottages
- Main risk
- Hollowed wood in damp areas, often a sign of moisture
- Risk level
- Moderate
Signs you have carpenter ants
- Large black ants indoors in early spring, sometimes before snow melts
- Piles of coarse sawdust-like frass mixed with insect parts
- Winged ants coming from walls, window frames or ceilings in spring
- Faint rustling sounds inside walls at night
- Ant trails from trees or woodpiles to the house after dark
- Soft, damaged wood near leaks, decks or window sills
Why carpenter ants are common in Michigan
Michigan has a lot of trees, a lot of lakeside moisture, and a lot of older wood-frame homes. Carpenter ants love that combination. Their main colonies often live in dead trees, stumps or old firewood. From there they send workers out to forage, and they set up satellite nests in houses where wood has stayed damp for a long time.
Cottages and cabins in the Northern Lower Peninsula and the Upper Peninsula see them often, especially places surrounded by woods or built close to the water. In Metro Detroit and other suburbs, the problem spots are rotted window frames, roof and chimney leaks, poorly flashed decks and porch columns, and bathrooms with slow leaks under the tub.
Seeing a few large ants indoors in March or April, while there is still snow on the ground, is a strong hint that a nest is inside the structure, since outdoor colonies are not active yet. Ants seen only in midsummer are more likely foragers coming in from a tree or stump outside, which is still worth tracking down.
Carpenter ants or termites
Both can swarm in spring and both affect wood, so people mix them up. Carpenter ants have a narrow, pinched waist, elbowed antennae, and front wings that are longer than the back wings. Termite swarmers have a thick waist, straight antennae and four wings of equal length. See our termite guide for more on telling them apart.
The damage looks different too. Carpenter ant galleries are smooth and clean, almost sanded, and the ants push out frass that looks like coarse sawdust mixed with bits of insects. Termite galleries are packed with mud and soil, and termites leave no sawdust piles. If you find a frass pile under a window or in the basement, look straight up for the source.
How carpenter ant treatment works
The goal is to get the colony, not just the ants you see. Technicians follow foraging trails at night, check for frass, and look for moisture problems around the house. Treatment usually combines slow-acting baits that workers carry back, a dust or foam applied into the nest void, and a perimeter treatment outdoors around the foundation.
Fixing the moisture is part of the job. If the leak or rotted wood stays, ants will likely return the next spring. Replace damaged wood, fix gutters and flashing, and keep plants and branches trimmed back from the siding. Many cottage owners pair a spring treatment with a quick check of roofs and decks when they open for the season.
What you can do yourself
- 1Follow ants with a flashlight after dark to see where they enter the house.
- 2Fix roof leaks, plumbing leaks and gutter overflow, and replace soft, rotted wood.
- 3Trim tree branches so they do not touch the roof or siding.
- 4Stack firewood away from the house and off the ground.
- 5Remove old stumps and dead trees near the home where practical.
- 6Use ant baits labeled for carpenter ants along trails, following the label.
When to call a licensed pro
- You see carpenter ants indoors in late winter or early spring.
- You find frass piles or winged ants coming out of a wall or ceiling.
- Baits have not stopped activity after a few weeks.
- You own a cottage or cabin that sits empty and needs a seasonal plan.
What carpenter ants treatment costs in Michigan
$200 to $600per treatment
Typical Michigan ranges, not quotes. The price depends on how hard the nest is to reach, the size of the home, and whether a follow-up or seasonal plan is included.
Typical ranges, not quotes. See the full Michigan pest control cost guide.
Carpenter ants: common questions
Do carpenter ants eat wood?
No. They chew galleries in wood to nest but do not digest it. They eat other insects, honeydew from aphids and sweet foods. The damage builds slowly, usually over years, and is mostly found in wood that has already been softened by moisture.
Why do I see carpenter ants in winter?
Ants active indoors in January or February usually mean a nest is inside the warm part of the house, often in a wall near a heat source or a leak. Outdoor colonies are dormant during a Michigan winter, so winter activity is worth an inspection.
Are carpenter ants as bad as termites?
Usually not. Termites eat wood and can cause more widespread damage. Carpenter ant damage tends to stay near wet areas. Still, a long-term nest in a wall, sill plate or roof can weaken wood, so it is worth treating and fixing the moisture.
When should I have my cottage treated?
Spring is the best time, as ants become active and before they build up in the structure. Many cottage owners in northern Michigan schedule an inspection when they open the place for the season. Check our pest calendar for other spring pests.