Carpenter ants are among the largest ants found in the United States, ranging from 1/8 to ½ inch long, the queens are slightly bigger. The workers of an established colony vary in size. They are commonly black; however, some species are red and black, solid red, or brown in color. They have one node in the petiole and a circle of tiny hairs on the top of the abdomen. Their thorax is evenly rounded when seem from the side.
The adult winged female or queen loses her wings soon as mating with the smaller male and selects a secluded nesting site where she raises the first brood of workers. These workers are very small but assume the care of the larvae and the queen after they mature. Future workers are larger than those from the first brood because they receive better care. All workers are wingless.
Mature colonies range in size from several thousand workers to an average of 20,000. When raised at 90°F, black carpenter ants complete their life cycle (egg to adult) Swarmers do not appear in the colony for several years, usually from three to four years up to six to ten years. Swarming for these species occurs May through August and February through June, respectively.
Carpenter ants are social insects that usually nest in wood. They commonly excavate galleries or tunnels in rotting or sound trees and, in structures, readily infest wood, foam insulation, and cavities. They prefer to excavate wood damaged by fungus and are often found in conjunction with moisture problems.
The workers excavate the nest, forage for food, and care for the young. Carpenter ants feed on sugar solutions from honey dew-producing insects such as aphids, sweets, and the juices of insects they capture. They do not eat the wood as they excavate their nests. They actively feed at night well after sunset continuing through the early morning hours. Foraging may extend up to 300 feet and, upon close inspection, can be seen on the ground as narrow worn paths.
Carpenter ants enter structures through gaps or cracks while foraging for food. However, the appearance of large numbers of winged adults inside a structure indicates that the nest(s) exists indoors. The workers push wood shavings and pieces of foam insulation out of the nest through slit-like openings in the surface of the wood or other nesting site material. This material, which may contain fragments of other insects, and structural moisture problems are things to look for when trying to locate a colony in an infested structure. Rustling sounds in wall voids are another indication that there is a colony in the area.