Carpenter ants are the most common wood-destroying insect in Maine, far more prevalent than termites in the state’s cold climate. The eastern black carpenter ant (Camponotus pennsylvanicus) is the primary species homeowners encounter, and its preference for moist, softened wood makes Maine’s older homes, wooded lots, and long winters a perfect combination for infestation. Here’s what you need to know to identify them, understand the damage they cause, and keep them out of your home.
What Carpenter Ants Look Like
Maine’s carpenter ants are large, typically 1/4 to 1/2 inch long, and mostly black. They’re noticeably bigger than the small pavement ants you might see on a sidewalk. Workers have a single-segment waist (the narrow pinch between the thorax and abdomen), which distinguishes them from termites, whose bodies look more like a straight tube.
During mating season in late spring and early summer, you may spot winged carpenter ants leaving an established colony for mating flights. Queens have wings initially but shed them after mating. Males also have wings but are smaller than queens. If you see large winged ants inside your home during winter or early spring, that’s a strong signal a colony is nesting in your walls, since outdoor colonies wouldn’t be active yet.
When They’re Active in Maine
Carpenter ants are active outdoors roughly from early May through the end of September. They emerge in spring as sunlight warms their nests, and mating flights happen in late spring and early summer. Development from egg to adult takes about three months during warm weather.
In heated buildings, the timeline shifts. Ants inside your home may stay active later into fall and start moving earlier in spring than outdoor colonies. Year-round activity indoors, especially in winter, almost always means a colony has established itself inside the structure rather than just foraging from outside.
How to Tell You Have an Infestation
Carpenter ants don’t eat wood. They chew out coarse, sawdust-sized pieces to create smooth galleries where they live and raise their young. This is the key difference from termites, which actually consume the wood. The “sawdust” (called frass) gets pushed out of the nest through cracks in the wood or through oval exit holes about 1/8 inch across. Finding small piles of wood shavings near baseboards, window frames, or in a basement is the most reliable sign of an active colony.
Other signs include hearing faint rustling sounds inside walls, seeing individual large black ants trailing through your kitchen or bathroom (especially at night, when they forage most), and finding shed wings near windowsills in spring. Over time, the galleries honeycomb the wood and can compromise its structural strength. Most damage accumulates during the warm summer months when the colony is most active and growing.
Carpenter Ants vs. Termites
Maine homeowners sometimes worry about termites, but carpenter ants are a far more common threat in the state. The frass is the easiest way to tell them apart: carpenter ant frass looks like coarse wood shavings, sometimes mixed with insect body parts, while termite frass resembles tiny pellets. Carpenter ant galleries are clean and smooth inside, almost sandpapered in appearance. Termite tunnels are rougher and packed with mud-like material. And physically, carpenter ants have a defined narrow waist and elbowed antennae, while termites have straight antennae and a thick waist.
Why Maine Homes Are Vulnerable
Carpenter ants are opportunists that prefer moist, softened wood. They can tunnel through dry wood, but they strongly favor areas where water damage, condensation, or leaks have already weakened the material. Maine’s climate creates plenty of these conditions: ice dams in winter, spring snowmelt, humid summers, and older homes with aging roofs and plumbing. Common nesting sites include rotting windowsills, wood around sinks and bathtubs, leaky roof areas, and porch supports in contact with soil.
Carpenter ant colonies also operate with a parent colony and satellite colonies. The parent colony, which contains the queen and requires consistent moisture, is often located outdoors in a dead tree stump, a woodpile, or a standing dead tree on your property. Satellite colonies branch off and can establish inside your home’s walls, attic, or crawlspace. This means the ants you find indoors may be commuting from a nest 100 feet or more away, traveling along tree branches, utility lines, or fence rails that touch your house.
Prevention That Actually Works
The most effective prevention targets the two things carpenter ants need: moisture and access. Fixing leaky roofs, windows, doorframes, and plumbing removes the conditions that attract them in the first place. Replace any water-damaged or previously infested wood, and paint or seal exposed wood before it has a chance to absorb moisture. Eliminate any spots where wood directly contacts soil, like deck posts or siding that reaches ground level.
Around your property, trim all trees and bushes so no branches touch the house. These act as direct highways for ants moving between outdoor nests and your structure. Store firewood off the ground on a concrete pad, well away from the house, and only keep one season’s worth at a time. The longer a woodpile sits undisturbed, the more likely it becomes a colony site. Remove dead tree stumps from your yard, and seal openings in living trees, which are attractive nesting spots. Spraying firewood with insecticides isn’t recommended and doesn’t help.
How to Get Rid of an Active Colony
If you’re dealing with a small number of foraging ants, bait products containing boric acid or liquid borax (such as Terro Ant Killer II) labeled for carpenter ants can work as part of a control program. Place baits along the trails where you see ants traveling, and keep them out of reach of children and pets. Baits work slowly because foraging workers carry the material back to the nest, where it gradually spreads through the colony. This process takes time, sometimes weeks.
For colonies nesting inside walls, dust-based insecticides are the most effective option because they can be injected into wall voids and other enclosed spaces. Treating the nest directly produces the fastest results. Crack-and-crevice treatments along baseboards and entry points take longer because they rely on workers carrying enough product back to the colony to kill it.
Many Maine homeowners ultimately call a professional, especially when there are multiple satellite colonies or when the nest location isn’t obvious. A standard one-time treatment for an average-sized home runs $250 to $500. Smaller homes with an accessible nest might cost $150 to $300, while severe infestations requiring wall void drilling or treatment of multiple nests can reach $500 to $1,200 or more. National chains like Orkin and Terminix typically charge $300 to $1,000 depending on severity, or offer year-round pest management plans running $50 to $80 per month. Recurring quarterly plans from various companies average $40 to $70 per month and include retreatments.
How Much Structural Damage to Expect
Carpenter ant damage is slower than termite damage but can be just as serious if left unchecked for years. A mature colony of several thousand workers, actively excavating galleries in structural lumber, can weaken floor joists, wall studs, and roof framing over the course of several seasons. The damage tends to concentrate in areas that were already moisture-compromised, so what starts as a minor leak can become a structural repair if carpenter ants exploit the softened wood.
The good news is that most infestations caught within the first year or two cause cosmetic rather than structural damage. If you’re finding frass piles but the wood still feels solid when you tap or probe it, you’re likely catching things early. The longer a colony goes unnoticed, particularly in hard-to-inspect areas like behind bathtub walls or in attic rafters, the more extensive the excavation becomes. In Maine, where homes may sit closed up for parts of the winter while colonies inside stay warm and active, checking vulnerable areas each spring is worth the effort.