Carpenter Ants

INTRODUCTION. The black carpenter ant, Camponotus pennsylvanicus (DeGreer), is a native species and the common species in the east. Camponotus modoc Wheeler is the common western species. 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. Carpenter ants are found throughout the United States.

RECOGNITION. Workers polymorphic, large (1/8-1/2" or 3.5-13 mm) but vary greatly in size; queens about 112-518" (13-17 mm) long. Color black, combinations of red and black, or completely red or brown. Antenna 12-segmented, without a club. Thorax lacks spines, profile evenly roundedd on upper side. Peel 1-segmented. Gassier with anal opening round, surrounded by circlet of hairs. Stinger absent. Workers capable of emitting a strong formic acid odor.

Camponotus pennsylvanicus with workers about 1/4-1/2" (6-13 mm) long and completely black except top of gaster with long, pale yellowish hairs pressed against its surface. Camponotus modoc with workers about 1/4-1/2" (5-11 mm) long, dull black with reddish legs and with golden hairs covering abdomen. Queens up to 5/8+" (17+ mm) long. 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.

SIMILAR GROUPS. (1) Dark field (Formica spp.), larger yellow (Acanthomyops interjectus), and Allegheny mound (F. exsectoides) ants have profile of thorax not evenly rounded, with distinct impression(s); in addition dark field ants with front and hind margins of node steeply or equally sloped. (2) Velvety tree ants (Liometopum spp.) lack circular anal opening surrounded by circlet of hairs. (3) Other medium to large dark ants with 2-segmented pedicel.

DAMAGE. The only external indication of infestation other than the presence of workers and/or swarmers is the appearance of small openings or windows on the surface of the wood. Through these, the workers expel debris which consists of sawdust-like shavings and/or fragments of insulation and insect body parts. The accumulation of such debris 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.

They prefer to attack wood softened by fungus and are often associated with moisture problems.

BIOLOGY. Black carpenter ant colonies are of moderate size, usually containing over 3,000 workers (up to 10-15,000 including satellite nests) when maturity is reached in about 3 to 6 years. The typical western carpenter ant (C. modoc) mature colony contains about 10-20,000 workers, with large colonies having up to 100,000 workers. Developmental time (egg to adult) for workers takes at least 60 days. Workers are polymorphic, with majors, minors and intermediates present. There is usually only one functional, wingless queen per colony. Swarmers are not produced until the colony is more than 2 years old, usually 3.5-4 years old for C. pennsylvanicus and often 6-10 years old for C. modoc. Swarmers appear from May until August in the east and from February through June in the west.

HABITS. Most carpenter ant species establish their first nest in decayed wood and later expand or enlarge this into sound wood. Inside, nests are located in wood (preferably softened by fungus rot), in insulation, and/or in wall voids. 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 stones or fallen 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 (91.4m) from the nest. They typically enter buildings around door and window frames, eaves, plumbing and utility lines, 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. The trail between the parent and satellite nest is usually about 1/4-13/16" (6-20 mm) wide and is kept clear of vegetation and debris. It usually follows contours but typically will cut across lawns.

CONTROL. The first step is to determine if the ants present are merely foraging inside or if there is a nest 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, check around the building's perimeter for foraging trails, especially in the direction of trees and shrubs; easiest to locate between sunset and sunrise when the ants are most active.

The second step is to locate any inside nests. Look for sawdust piles with insect body parts. Listen for ant sounds mentioned above; listening devices are helpful. Gently tap with a screwdriver, etc. all exposed wood such as floor joists, sill plates, roof rafters, etc. and listen for sound changes; nest cavities give a hollow or dull ring. Check suspicious areas with a knife blade which will readily penetrate infested wood. Be sure to check crawl spaces, basements, and attics. Carpenter ants have a network of trails they follow throughout a structure and often use the tops of electrical Wires and water pipes, so be sure to check where these are. A moisture meter can be helpful in locating areas of higher moisture in which the ants prefer to locate their initial nests.

The third step is to determine if the inside colony is a parent or satellite colony. Inspect and search. Detection of a trail directs one to the parent colony. For effective control, it is imperative to locate and eliminate the parent colony.

Once the colony or colonies are located, they should be treated directly with an appropriately labeled pesticide. Inside, this may involve drilling wall voids and applying dust and/or drilling wood members and pressure injection. Barrier treatment is effective in preventing entry, with wettable powder and microencapsulated formulations working best. All branches of trees and shrubs in contact with the building must be trimmed back. Be sure to check where electrical and water lines enter the building and caulk any gaps. Sometimes treating the bottom 3-6 feet (1-2 m) of tree trunks and/or utility poles is helpful.

Fire Ants

INTRODUCTION. These ants get their common name from their ability to inflict especially painful bites and stings. The two most important species are the southern fire ant (Solenopsis xyloni McCook) and the red imported fire ant (Solenopsis invicta Buren). The southern fire ant is a native species and ranges from California to southern South Carolina to northern Florida. The red imported fire ant is from central Brazil and is found in the southeastern United States, from Virginia through Texas.

RECOGNITION. Workers polymorphic, about 1/16-1/4" (1.6-6 mm) long; queens average 1/4" (6.6 mm) long. Head and thorax yellowish red and abdomen black; reproductives darker. Antenna 10-segmented, with 2-segmented club. Thorax lacks spines, profile unevenly rounded. Pedicel 2-segmented. Stinger extruded in most alcohol-collected specimens; readily inflict painful stings.

Characteristics of the mandible and petiole (1^st node of pedicel) will separate these 2 species. The mandible of S. xyloni has 3 distinct teeth on its inner/biting surface whereas, those of S. invicta have 4 teeth and the petiole of S. xyloni has a ventral tooth near the node's attachment to the thorax whereas, S. invicta lacks such a tooth.

SIMILAR GROUPS. (1) Fire ant (Solenopsis geminate) with ridge on lower front margin of mesothorax having 1 or more teeth, 1^st node in profile with rear margin almost straight. (2) Little black ant (Monomorium minimum) with antenna 12-segmented, club 3-segmented. (3) Acrobat (Crematogaster spp.), big-headed (Pheidole megacephala), harvester (Pogonomyrmex spp.), and pavement (Tetramorium caespitum) ants have spines on upper surface of thorax; in addition acrobat ants with heart-shaped abdomen and pedicel attached to upper surface of abdomen, big-headed ants with soldier with head very large and 3-segmented antennal club, harvester ants with underside of head with a brush of long bristles (coarse hairs/setae called psammophores), and pavement ants with head and thorax covered with distinct ridges. (4) Other small dark ants have 1-segmented pedicel.

BIOLOGY. For the red imported fire ant, single-queen mounds usually number 30-100/acre (0.4ha) with typically 80,000 but up to 250,000 individuals per colony. Multiqueened colonies may number 200-700/acre (0.4ha) but contain fewer individuals per colony, and there is less fighting between the colonies. Typical mounds are rounded, being up to 18" (48 cm) high and 24+" (61+ cm) in diameter, each with several tunnels just under the soil surface extending out several feet. A queen in a large colony is capable of producing her own weight in eggs each day or about 1,500 or more. Developmental time (egg to adult) for workers ranges from 22-38 days. A mature colony can produce as many as 4,500 swarmers during the year, with 6-8 mating flights occurring between spring and fall. Mating flights usually begin about 10 am, 1-2 days following a rain if it is warm (about 75 degrees F / 24 degrees C), sunny, and not very windy. Minor workers live 30-60 days, intermediates (medial) 60-90 days, and majors 90-180 days or longer. Queens live 2-6 years. Males die shortly after mating.

Typical mounds of the southern fire ant are flattened and irregular, covering 2-4 sq ft (0.17-0.37 sq m). Swarms occur from May through October in the afternoon to early evening of warm days. Developmental time can require as few as 44 days. Its biology has not been thoroughly studied.

HABITS. Fire ants are typically ground-nesting ants. However, the southern fire ant will sometimes nest in the wood or masonry of buildings, especially in areas near the soil or warmth such as fireplace hearths. When the southern fire ant nests outside near a house, it is usually in the vicinity of the kitchen. Outside nests are usually situated under stones or other covering objects, or in the soil at the base of a tree or shrub, or in clumps of grass.

The red imported fire ant typically nests outside. Each colony has its own territory, and there is usually no movement between colonies. However, they will sometimes nest in areas of exposed soil within buildings such as bath traps. They also have the habit of building outside nests adjacent to foundation walls. They are commonly introduced into new areas via potted or balled shrubs and trees.

Fire ants are attracted to electrical junction boxes of traffic signals, air conditioners, etc. When they mass around the electrical contact points, they cause the equipment to malfunction. They will also nest in gas and water meter boxes and then follow the pipes into the building.

Fire ants prefer food with a high protein content but will feed on almost anything, plant or animal. The southern fire ant has been known to remove insulation from phone and electrical wires, and to gnaw on clothing, especially if soiled. They usually feed on seeds, insects, young tree bark, honeydew and other sweets, preferring oily meats and nuts.

Red imported fire ants are particularly destructive to vegetation. Workers forage in established trails.

CONTROL. Fire ant control is difficult. It usually requires repeated applications of liquid or granular residuals to eliminate the colony. Particularly effective with a single application are residual aerosols applied under high pressure (160 psi) with a long injection probe.

Although baits are slower acting, they are effective. Baits containing only a stomach poison require several applications each season to control newly emerging workers when the queen(s) is/was not killed, and new colonies. Baits containing only an insect growth regulator can provide year-long control with 1 or 2 applications in the residential situation when followed in 7-10 days with a liquid residual application to kill the active foragers. Newer baits containing avermectin,, which acts as both an insect growth regulator and slow-acting stomach poison, give good control without liquid application.