Western Carpenter Ant  (Camponotus modoc)

Quick Look Pest Stats

Color: Red, black, or a combination

Legs: 6

Shape: Segmented; oval

Size: 1/2″ – 5/8″

Antennae: Yes

Region: Throughout the US




The common western species is dull black with reddish legs and golden hairs covering the abdomen. Other species are black, a combination of red and black or completely red or brown.


Carpenter ants hollow out spaces in wood to use as nests. Most species nest first in decayed wood and then enlarge the nest into sound wood. Indoor nests are in wood (perhaps softened by fungus rot), insulation, wall voids. Outdoor nests are in old firewood, rotting fence posts, stumps, dead portions of living trees, under stones and logs. A colony has a main nest connected to satellite nests by a cleared trail about 1/4 inch wide.


Outdoors: plant juices, insects, honeydew from insects, spiders. Indoors: sweets, grease, meat, eggs. Carpenter ants follow a regular trail when foraging.


A mature colony of western carpenter ants may have 10,000-20,000 workers or up to 100,000. Swarmers aren’t produced until the colony matures. In the West, swarmers may appear between February and June. There is usually just one functional, wingless queen per colony. Development from egg to adult takes at least 60 days.


The hollowing of wood for nests can weaken a structure. Also, bites can be painful.


Carpenter ants require a water source. To prevent these ants in the house, eliminate sources of moisture or standing water. Keep tree branches and other plants cut back from the house. Sometimes pests use these branches to get into your home. Make sure that there are no cracks or little openings around the bottom of your house. Make sure that firewood and building materials are not stored next to your home. Carpenter ants like to build nests in stacks of wood.


Look for piles of sawdust-like shavings, sometimes with bits of insulation and insect parts. Listen for rustling sounds from within the walls. (A listening device is useful.) Watch for foraging trails outside, especially between 10 am and 2 pm. Be alert to the emergence of swarmers. With a tool gently tap exposed wood and rafters, listening for a hollow sound which might indicate a nest cavity. A knife blade will easily sink into the wood if a nest is present. Check attics, basements, and crawl spaces. Check wires and pipes. Locate high moisture areas. (A moisture meter can be useful.)


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