Gaster with anal opening round, surrounded by circlet of hairs. Workers capable of emitting a strong formic acid odor. Other species black, various combinations of red and black, or completely red or brown. Although carpenter ants do not sting, their bites can be quite painful, especially when they inject formic acid into the wound. Other medium to large dark ants with 2-segmented predicel.
Workers are polymorphic, with majors, minors and intermediates present.
There is usually only one functional, wingless queen per colony. Swarmers appear from May until August in the east and from February through June in the west. Most carpenter ant species establish their first nest in decayed wood and later expand or enlarge this into sound wood. Workers are a nuisance when out searching for food but are destructive to timbers, utilized for nesting activities. Outside, nests are typically located in rotting fence posts, stumps, old firewood, dead portions of standing trees, and under stories of fallen logs.