These ants get their common name from their habit of hollowing out galleries in pieces of wood for nesting purposes. This nesting habit can result in structural damage. Fifty species of carpenter ants are found in the United States and Canada, 26 of which have been found to nest in structures.
Carpenter ant workers vary greatly in size, measuring 1/8 to 1/2 inch long. Queen ants measure 1/2 to 3/4 inch long. Depending on the species, these ants may be totally black, combinations of red, orange, yellow and black, or completely red or brown. The thorax profile is evenly rounded on the upper side. The waist (pedicel) is 1- segmented (one node). Carpenter ants do not have a sting. However, larger species can inflict a painful pinch using their jaws (mandibles); grasped workers are capable of emitting a strong formic acid odor. The four most common structure-infesting carpenter ant species in Missouri are:
Black Carpenter Ants
(Camponotus pennsylvanicus) have workers that measure 1/4 -1/2 inch long; they are completely black except for fine pale yellow hairs on top of the gaster (plump part of the abdomen). The queens can reach 3/4 inch in length. This species is common in both rural and urban settings and is responsible for most of the carpenter ant-related damage to structures in Missouri.
Rust-Colored Carpenter Ants
(Camponotus chromaiodes; a.k.a., Camponotus ferrugineus) and New York carpenter ants (Camponotus noveboracensis) have workers that measure 1/4 to 1/2 inch long and have the head and gaster mostly black and the thorax and legs mostly reddish. Queens measure 5/8 to 3/4 inch long. These latter two species occur more commonly in rural settings and wooded areas.
Nearctic Carpenter Ants
(Camponotus nearcticus) have workers that measure 1/8 to 3/16 inch long and may be completely glossy black or mostly black with a red thorax and legs. The queens can reach up to 5/16 inch long. This small species is common in both rural and urban settings. Structural damage caused by the excavation of these ants in buildings does not usually reach the scope of damage resulting from black and rust-colored carpenter ant activity.
Field ants (Formica species) have the profile of the thorax not evenly rounded. The upper side has a distinct notch half way or father back along the length of the thorax.
The only external indication of infestation other than the presence of workers and/or swarmers (winged queens and males) is the appearance of small openings or windows on the surface of wood. Through these, the workers expel debris, which consist of sawdust-like shavings, fragments of insulation and insect body parts. The accumulation of such debris (frass) below such holes is a good indication of an infestation. Inside, the galleries follow the softer spring wood with numerous connections through the harder/dark summer wood. The gallery walls are smooth, with a sand-papered appearance. The active galleries are kept clean of debris. These ants prefer to attack wood softened by moisture and fungal rot; therefore, they are often associated with long-term moisture problems in structures.
Black carpenter ant colonies are of moderate size, usually containing over 3,000 workers (up to 15,000, including satellite nests) when maturity is reached in about 3 to 6 years. Developmental time (egg to adult) for workers takes at least 60 days. Workers are of different sizes (polymorphic) with majors, minors and intermediates present. There is usually only one functional queen per colony. Once established, she chews off her wings and remains wingless for the duration of her life. Swarmers are not produced until the colony is more than 2 years old, usually 3.5 to 4 years old for C. pennsylvanicus. Swarmers appear from May until August.
Most carpenter ant species establish their first nest in decayed wood and later expand or enlarge this into sound wood. Indoors, nests may be located in wood (preferably softened by fungal rot), in insulation (including rigid foam board) and in wall voids. Workers are a nuisance when out searching for food but are destructive to woodwork utilized for nesting activities. Outside, nests are typically located in rotting fence posts, stumps, fallen trees, old firewood, dead portions of standing trees, and under stones and rotting logs. The presence of a carpenter ant nest is sometimes indicated by a rustling sound coming from wall voids or from wood where the colony is located. Otherwise, the emergence of swarmers indoors may be the first indication of an indoor colony. Carpenter ants feed primarily on insect honeydew, plant and fruit juices, insects and other arthropods. Inside, they will also feed on sweets, eggs, meats, cakes and grease. The workers forage for distances of up to 300 feet from the nest. They typically enter buildings around door and window frames, eaves, plumbing and utility line penetrations and shrub and tree branches in contact with the building. Although some workers are active during the day, most activity is from dusk till dawn, with peak activity between 10 pm and 2 am.
All branches of trees and shrubs in contact with the building must be trimmed back. One should check where electrical and water lines enter the building and caulk any gaps. On warm evenings, a night-time inspection of the ground and outside walls around the residence will reveal carpenter ant trails, activity sources and entry points. These observations should be reported to your Rottler technician in order to speed the process of colony location.
The first step for the Rottler pest management professional is to determine if the ants present are merely foraging inside or if there is one or more nests inside. The best indication of a nest is the presence of sawdust piles containing insect body parts. Another indication is the sound produced as the workers remove wood to expand the nest. Outside, the technician will check around the building's perimeter for foraging trails, especially in the direction of trees and shrubs. [Trails are easiest to locate between sunset and sunrise when the ants are most active; therefore; the property-owner's overnight observations would prove valuable to the attending technician.]
The second step is to locate any inside nest(s). The technician will look for sawdust piles with insect body parts and listen for ant sounds as described above; listening devices are helpful and may be used. Gentle tapping with a sounding tool of suspect structural wood, such as floor joists, sill plates, roof rafters, threshold kick-plates and deck attachment boards may elicit sounds that reveal the presence of nest cavities, which give a hollow or dull ring. Carpenter ants have a network of trails they follow throughout a structure and often use edge lines, the tops of electrical wires and water pipes. These features will be examined by the technician.
The third step is to determine if the inside colony is a parent or satellite colony. This is accomplished through inspection and observation of activity. Detection of a trail will direct the technician to the parent colony. If the colony or colonies are located, the technician will treat them directly using appropriately labeled residual and non-residual insecticides. Inside, this may involve drilling wall voids and injecting an insecticide aerosol or dust formulation or drilling wood members and injecting them with residual insecticide. Exterior perimeter barrier treatments with water-based residual formulations are effective in preventing carpenter ant entry. Sometimes treating (banding) the bottom 3 to 6 feet of tree trunks and/or utility poles is helpful. Strategically-placed insecticide baits are helpful in controlling ant colonies that cannot be pin-pointed within a structure on the premises or off-site. A quarterly pest management service program may be required in cases where large populations of carpenter ants are present in the environment surrounding the premises and where landscaping conditions are conducive to their propagation.