Carpenter Ants


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Black Carpenter ants (Camponotus pennsylvanicus) are one of the most common indoor pests found in new England. When these large black or black and red ants invade buildings, they often construct their nests in moist wood. Unlike termites, carpenter ants do not eat wood, but they do damage wood as they excavate to make room for their growing colony. Carpenter ants devour scavenged insects and collect carbohydrate secretions (honeydew) produced by aphids feeding on outside vegetation. These ants also wander around the inside of the house looking for sweets. Carpenter ants arouse concern when worker ants or winged swarmers are discovered inside and the first thing people usually ask is, how do I get rid of them?

Interesting Carpenter Ant Facts


It is important to identify your ants. Collect a few specimens on scotch tape or in vials and send them (dead) in an envelope to your local university or extension office for identification. Worker carpenter ants from a single colony range in size from small (1/4 inch) up to large (1/2 inch). Carpenter ant queens are as large as 3/4 inch. Foraging ants are usually active on the floor as well as counters and shelves. During warmer days a number of winged ants may swarm inside and they are usually trapped near a window as they try to escape towards the sun. By the way, when you see winged ants, you can predict that the nest is probably over three years old and may have more than 3,000 workers. When termites swarm, they drop their wings immediately while carpenter ants retain their wings as they look for a new nest site.

There are three common species of carpenter ants that regularly invade homes in New England:


The black carpenter ant in nature occurs primarily in forested areas, where it nests in the dead wood of standing trees, fallen logs, and in stumps. It can be found in many forest types, and is especially abundant in eastern and central Massachusetts, and at lower elevations in western Mass. In natural ecosystems, Carpenter ants play an important role in the ecologically vital process of decomposing wood back into soil. The workers are also significant predators of many small invertebrates (including forest pest species), and they maintain mutualistic relationships with aphids and coccids. They are thus highly beneficial organisms. Unfortunately, their wood-dwelling habits pre-adapt them for living in houses. In these situations only do the ants become significant pests and require control.

Carpenter ants excavate through the wood parallel to the grain. Their galleries are free of debris and appear to have sandpaper-like walls. The coarse shreds of wood, often called frass, are ejected out of small openings in the wood into sawdust-like piles. Often bits and pieces of dead carpenter ant fragments are mixed with the debris. If the galleries are close to the surface of the wood, and the ant colony size is large, the sound of many mandibles scraping along inside the wood can be faintly heard. And if the nest is disturbed, the major workers may bang their head and gaster against the sides of the galleries making a faint vibrating sound.

Carpenter ants forage predominately at night but during early spring and summer they will also forage during the day. During the first year, when colonies are small, almost all of the workers are small, minor workers. Both major workers and minor workers are out foraging when the colony size is large. Although carpenter ants have strong mandibles, they rarely come into contact with people, and when they do, instead of trying to bite, they try to escape. Carpenter ants cannot sting; instead they squirt formic acid at their enemies. Control

Nest Location

The single most important task is to locate the carpenter ant nest. Worker ants must leave the nest on a regular basis (they are most active at night during the summer) and search nearby vegetation for food. You can search the perimeter of the house along the foundation looking for ants on their return trip to the nest. Any trees with limbs or branches touching the building will allow ants to sky-bridge across and therefore all tree branches should be pruned away from the house. Follow a few workers patiently and you will find that all ants return to the same location. In a few cases there may be more than one nest in a building. Since carpenter ants nest in damp wood, usually with moisture content greater than 15 %, the number of nests may depend on the number of moisture problems. This moist wood is often found under dishwashers, along gutters that have plugged up with leaves, under the ledges of windows when the paint is peeling, under wood decks holding water against the house and next to plumbing leaks. Also nests are found along leaking chimney flashing, leaking skylights, and under bathtubs. Outside, nests occur in rotting portions of trees, dead stumps, and in wood landscaping ties. It is a good idea to remove all wood away from a building and to make sure that none of the wooden part of the house is in direct contact with the soil.

If you are having trouble locating the nest, you might try the following steps: * Start from nearby trees and other vegetation and follow ants back to the nest. Returning ants take a more direct route than ants searching for food and their abdomens are often expanded with honeydew. * Listen for chewing sounds. Carpenter ants make a scraping noise as they excavate wood for their galleries. Look for wood debris or sawdust and ant parts that are ejected from the nest. * Put out a sweet food source such as dilute honey or jam and follow ants from your bait back to their nest.

Control measures you can do on your own

Once the nest has been located, the next step is to eliminate the ants inside. First you may want to try several measures yourself.


If you prefer to use a pest control vendor, then the following guidelines should help you choose a reputable firm. 1. Obtain two or more estimates for control. The company you choose should have located the nest or probable nest site before treatment. See if both companies agree on the same nest location. 2. Is safety measures part of the pest control service? Are you provided with a material safety data sheet that indicates hazards and are you given a fact sheet on carpenter ants? 3. If the nest is successfully eliminated and the moisture problem corrected, there is little concern that you will need additional service such as a yearly or monthly service. Be wary of signing a contract that requires additional costs and service. Ask for a guarantee that the nest will be eliminated or find a different pest control firm.

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