Carpenter Ants

Carpenter Ants, Camponotus spp. (Mayr)

Carpenter Ant Characteristics:

Adults vary in length (polymorphic)

Carpenter Ant

Carpenter Ant

Minor worker: ¼ inch (6 mm)Major worker: ½ inch (12 mm)
Winged Reproductives: up to 7/16 inch (18 mm)
Functional wingless queen: 9/16 inch (20 mm)
Coloration varies from solid dull black or yellowish-red to a combination of black and dull red or reddish-orange
Have only one segment or node between their thorax and abdomen
Have a circle of hairs at the tip of their abdomen
Have evenly rounded thorax when viewed from the side
Generally nest outdoors- indoor nests my be satellite colonies


Carpenter ants are highly adaptable and capable of establishing nests in diverse environments. They most commonly occur in wooded areas preferring to nest in a moist, humid environment. They nest in live or dead trees and stumps, dead tree limbs, buried wood, in firewood, fence posts, landscape timbers, tree holes, hollow wooden doors, ceiling beams, under roofing boards and attic insulation, voids above windows and porches, under rocks, logs and other objects on the ground. In structures, timbers damaged by water leaks attract these ants, and they select damp, soft, decaying areas for nesting sites. These ants prefer to nest in wood, but are capable of nesting in preformed cavities, or natural cavities, termite galleries, or even in exposed sites in boxes, cabinets or attics. Carpenter ants do not eat wood, but remove quantities of it to enlarge the nest for a growing colony. This activity may cause structural damage. When searching for food, carpenter ants feed mainly on honeydew produced by homopterous insects (aphids, mealybugs, and scales) that feed on sap from plant tissues.

Carpenter ants have an evenly rounded thorax when viewed from the side. The abdominal pedicel has a single segment, the petiole, between the thorax and gaster. A fringe of hairs surrounds the terminal cloacal orifice. Workers do not sting but are capable of biting and injecting formic acid in the pierced area, which can be quite painful. The worker caste is polymorphic.The black carpenter ants, Camponotus pennsylvanicus (DeGeer) have one inseminated queen in each colony, however, colonies of other species such as Camponotus vicinus (Mayr) may have multiple queens. A newly mated queen finds a suitable nest site and rears the first brood of small workers (minims). These first workers begin to build and expand the nest, gather food, care for the queen and the next batch of brood. The colony will grow slowly the first year with only about 10 to 15 workers produced. About twice that number will be produced the second year. Major workers will appear within six to ten years. Reproductive forms will appear shortly following the emergence of major workers. Typically the parent colony will be located outdoors; indoor colonies will be associated with water leaks.


There are 25 species of Camponotus in the United States and most are native species. There are an estimated 1,000 species worldwide. Most Camponotus occurring in the United States are considered pests of minor importance that only occasionally infest structures. The species most commonly encountered by homeowners are Camponotus pennsylvanicus (DeGeer), called the black carpenter ant that occurs from the Atlantic seaboard to the Rocky Mountains. Campanotus pennsylvanicus is dull black all over including its legs and antennae and the abdomen is closely invested with long yellow hairs. The workers range in size from ¼ to ½ in. (7-13 mm). A single colony of black carpenter ants may contain 15,000 workers. Camponotus modoc (Wheeler) and Camponotus vicinus (Mayr) are found west of the Rocky Mountains. Camponotus modoc is black with dark red legs and workers range in size from 1/5 to ½ in. (7-13mm). Colonies of Camponotus modoc may contain up to 50,000 workers. Camponotus vicinus has a red thorax with the rest of the body and legs black. The workers range in size from ¼ to ½ in. (7-13mm) and may maintain very large colonies of 100,000 workers with multiple queens. The Florida carpenter ant, Camponotus floridanus (Buckley) is a pest in the southeastern United States. It is one of the most serious structural pests in Florida and the extreme southeast. Florida carpenter ants have yellowish red to red head, thorax, and petiole and the abdomen is black. Long yellowish hairs cover the body. The workers range in size from 1/5 to ½ in. (9-13 mm). Workers have a strong bite and are called “bull dog” or “bull ants” by Floridians. Camponotus floridanus ranges from North Carolina to Florida and west to Mississippi. Colonies may contain up to 8,000 individuals.


Effective control can be achieved if the parent colony and all satellite colonies are located. A thorough inspection should be performed to determine where the ants are nesting. Moisture is the most important factor in attracting and sustaining carpenter ants in structures. All water leaks should be eliminated. Damaged and decaying wood should be replaced with solid, dry lumber and cracks and crevices caulked, including openings for electrical and water lines that enter the building. Branches of trees that contact the side or roof of the structure should be trimmed in order to exclude ants that are nesting in trees. Piles of wood shavings are signs that carpenter ants are nesting nearby. Colonies can be located by following foraging ants back to their nesting sites. Treatment techniques used depends on where colonies are located and will also determine the type of insecticide needed. In the home, all insecticides should be applied only as crack, crevice or hole treatments. Approved dust formulations puffed into holes can give good coverage of voids where ants are active and can be killed or carry the chemical back into the nest, contaminating and killing others. Thin layers of an oil-based insecticide can be brushed into cracks along baseboards, window and door frames and around plumbing, electrical lines, and heating pipes can be effective. All colonies found outside should be treated directly with a residual contact spray. Perimeter and foundation treatments of structures with a liquid insecticide will help prevent outdoor foraging ants from entering. Spray applications to trees where carpenter ants are located are helpful.