Carpenter ants are large black or red-and-black ants that excavate galleries in damp, softened wood to nest. On Whidbey and Fidalgo they are the most common structural ant, favoring crawl spaces, decks, and window frames where coastal moisture has weakened the wood.
How to identify carpenter ants
Workers are 1/4 to 1/2 inch long, black or bicolored, with a single node and an evenly rounded thorax. Winged swarmers appear in spring. Unlike termites, they have bent antennae and a pinched waist.
Behavior & season on Whidbey & Fidalgo
Colonies stay active through our mild, wet season and forage at night along foundations, wires, and tree limbs touching the house. Peak swarming runs March through June. They do not eat wood — they hollow it out to nest, often in previously water-damaged framing.
Why carpenter ants are a problem
A mature colony builds satellite nests and can weaken structural wood over time. Because they target moisture-damaged areas, their presence usually signals a hidden water or ventilation problem in the crawl space or siding.
Signs of carpenter ants activity
- Large ants indoors, especially in spring
- Piles of fine, sawdust-like frass with insect fragments beneath wood
- Faint rustling in walls at night
- Winged swarmers at windows
How Salty Dog treats carpenter ants
We locate the parent and satellite nests, treat with non-repellent products the colony carries back, and identify the moisture source feeding them so the problem does not return. Learn more about our Carpenter Ant Control service, or browse the full Pest Library.
Reviewed by Matthew — Salty Dog Pest Control. WSDA-licensed structural pest applicator (License #101709). Veteran- and family-owned, serving Whidbey Island, Fidalgo Island, and west Skagit County.
Frequently asked questions
Are carpenter ants as damaging as termites?
They work slower than termites but a large, established colony can still cause meaningful structural damage — and they always point to a moisture issue worth correcting.
Why do I only see them in spring?
Spring swarms are the colony reproducing. Seeing winged ants indoors usually means an established nest is inside or against your home, not just outside.
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