Twenty-four species of carpenter ants are structural or nuisance pests in North America, although each species may be found in different regions. All carpenter ants can be recognized by the evenly rounded thorax when viewed from the side. Color is variable amongst the species, from black, red and black, to even a yellowish-brown. The black carpenter ant (Camponotus pennsylvanicus) is the most common species in the East; the western black carpenter ant (Camponotus modoc) is most common species in the West.
Carpenter ants are the largest pest ants that will be found infesting structures. Workers may measure up to one half an inch and queens may be even larger. However, carpenter ants are polymorphic and have several different sized workers. Most colonies establish satellite colonies near a parent colony that is usually outdoors in a tree or tree stump, firewood, landscape timber, etc. Although carpenter ants excavate wood, they readily establish satellite colonies in structural voids, especially near moisture. Colonies can be found by following foraging ants along their trails. Since carpenter ants are primarily active at night, nighttime inspections are more effective at locating their colonies. Finding piles of sawdust containing insect parts may also indicate that a colony is nearby.
The hardest part of carpenter ant management is finding all of the colonies, especially the parent colony, which may be located on a neighboring property. Gel bait can be placed along foraging trails and at structural entry points. Baiting alone has been successful for black carpenter ants. However, active trails are necessary in order for worker recruitment to take the bait back to the parent colony. When colonies are located, they can easily be treated with aerosol or dust formulations.