Symptoms
- Large black or reddish-black ants, noticeably bigger than typical kitchen ants
- Small piles of sawdust-like material (frass) near a wall, window, or baseboard
- Faint rustling sound inside a wall, especially at night
Likely causes
- CommonExisting moisture-damaged or soft wood attracting a nestCarpenter ants strongly prefer wood that's already damp or slightly decayed to tunnel through.
- CommonSatellite nest indoors connected to a larger outdoor colonyIndoor sightings are often a smaller offshoot nest, with the main colony outside in a stump or woodpile.
- PossibleDirect nest establishment in a wall void or structural woodIn some cases, especially with chronic moisture, a full colony can establish indoors.
What to do
- Look for frass piles, which resemble fine sawdust mixed with insect parts, near baseboards, window sills, or wall voids.
- Identify and fix the moisture source in the affected wood, since carpenter ants are drawn to and thrive in damp wood.
- Trace ant activity, especially any seen at night, to try to identify the general nest location.
- Avoid simply spraying visible ants, which doesn't address the nest and may scatter it into new areas.
- Remove woodpiles, stumps, or dead wood touching the house, which are common outdoor nest sites feeding an indoor satellite colony.
- Have a pest control professional inspect and treat the nest directly, since carpenter ant colonies usually need targeted treatment to fully eliminate.
- Repair any structurally damaged wood found once the colony has been eliminated.
Tools and parts
- Flashlight
When to call a pro
Call a licensed pest control professional to locate and treat a carpenter ant nest, and a carpenter to repair damaged wood.
Safety
Generally low risk
Generally low risk for a careful person. Stop if anything looks different from what this guide describes.