Carpenter Ants

Carpenter ants (Camponotus) are large ants. The NYS IPM Program puts workers at 1/4 to 1/2 inch and queens at up to 3/4 inch, in all black or two-toned black and red. Knockout Pest Control in Uniondale says they look like ordinary garden ants, only much bigger.

What carpenter ant damage looks like

Carpenter ants hollow out wood to make galleries. The NYS IPM Program says the gallery walls are smooth, and the ants push the debris out as piles of what looks like sawdust, called frass, often with bits of dead ants mixed in. The Connecticut Agricultural Experiment Station uses that as the main way to tell their work from termites: carpenter ant tunnels are clean, termite tunnels are packed with soil.

Knockout warns that the galleries can badly weaken load-bearing beams, and that a colony can number in the tens of thousands.

Signs a colony is inside

The NYS IPM Program lists four:

• small piles of frass under a window frame, door frame or beam
• workers foraging across floors, counters and shelves
• winged ants coming out indoors on a warm day, often at a window
• a scraping or chewing sound inside a wall

Two nests, not one

The NYS IPM Program describes a parent nest, usually outdoors in a rotting stump, dead tree limb or old timber edging a garden bed, where the queen lives. From it, the colony builds satellite nests in drier spots inside: attic rafters, floor joists, wall voids and hollow doors. The ants on the counter may be coming from a nest you cannot see, or from one outside.

Carpenter ants go for wood that is already damp or damaged. The program says a nest is a sign there is a moisture problem somewhere.

Finding where they are coming from

Carpenter ants forage at night, so that is when to look. The NYS IPM Program suggests putting out a dab of honey or jam on wax paper where you have seen them, then following the ants that carry food away with a flashlight. Ants heading home walk a straighter line. Check trees and shrubs close to the house too.

Winged carpenter ants and termite swarmers

Both come out with wings in warm weather and both end up on window sills. The NYS IPM Program’s quick checks: a carpenter ant has a pinched waist, bent antennae and two pairs of wings of different sizes. A termite has a thick waist, straight antennae and wings that match, and leaves silvery wing flakes behind after it swarms. If you are still not sure, our termite page lists the other termite signs to compare.

Fixing what draws them in

The NYS IPM Program calls fixing moisture the permanent fix. Its list:

• keep shrubs and tree branches at least six feet from the house
• clean clogged gutters and send downspout water away from the foundation
• repair damaged flashing, worn caulk and peeling paint
• fix leaking pipes and the seals around dishwashers, sinks and tubs
• replace rotted wood with pressure-treated wood and haul the old wood away
• keep wood from touching soil

For treatment, the program prefers fresh sugar baits labeled for carpenter ants, placed on their trails, over contact sprays.