Carpenter ants are named for their habit of excavating, tunneling and living in wood. Two kinds are of concern--the red carpenter and the black carpenter ant. Their habits and sizes are similar, but the latter is by far the more common.

Description:

Like honey bees, ants are social insects. An ant colony consists of workers and a queen. The workers are sterile, wingless females, 6-12 mm (1/4-1/2 inch) long. The smallest residents of the colony, the workers gather food and water to feed the colony and gnaw out wood to make the galleries in which the colony lives.

In two to five years, a colony with a good supply of food may form a reproductive or dispersal generation. This generation consists of winged males and females. Males, known as drones, are about 16 mm (5/8 inch) long; winged females from 16 mm to 22 mm (5/8 to 7/8 inch) long. Most drones die shortly after fertilizing the female°s eggs. The females shed their wings immediately after mating and become full-fledged queens. A 20 mm (3/4 inch) long, wingless ant is probably a queen carpenter ant. The queen looks for wet, rotten wood in which to start new a colony or join an existing one. A queen starting a new colony lays about 30 eggs and cares for the larvae until they are adult workers. This new generation of workers takes over the various chores in the colony and the queen's full-time job becomes laying eggs.

Habitat:

The forest is the carpenter ant's natural habitat. Carpenter ants infest live, dead or fallen trees wherever there is some rot and moisture. They play an important role in recycling wood in the forest. Buildings close to a forest with rotting logs and trees are likely candidates for carpenter ant infestations.

The nearer a water and food supply is to the nest, the faster an ant population increases, and the greater the need to enlarge the galleries to accommodate the colony. The process of excavation is what damages or weakens wooden structures. Tunneling can take place inside any piece of wood without visible signs of the process on the outside.

Carpenter ants do not eat wood, but rather tunnel to increase nesting space. In the forest, carpenter ants feed on sap, pollen, nectar, fruits, and both living and dead insects. Water is an important part of their diet.

In a house or other building, infestations may begin because of a water leak around the chimney, roof valley, gutter, window, door frame or space under wooden floors where there is no basement. Sill areas invite ants, especially if soil touches the wood. Wood from new construction provides an excellent nesting place. Kitchen and bathrooms also often provide ample moisture for ant infestations through leaks in water pipes or water-heating systems. Ants are often transported indoors on firewood.

Because carpenter ants are nocturnal, their presence is usually only noticeable when a colony is under stress because of lack of water, food or nesting space, or because they are in a reproductive generation.

Management:

The presence of large ants usually is the first sign of infestation. Coarse sawdust is a sure sign, but it is often difficult to find the nest. At night, turning on a light to observe ant activity around a sugary bait that has been left out may reveal an "ant line" to and from the nest. Sometimes the insects' activity can be heard in walls. Tapping areas suspected of harboring nests with a hammer may produce a hollow sound, and some excited ants may appear.

Boric acid has proven to be an effective ant control. Make a 1% Boric Acid and 20% sugar solution by thoroughly dissolving 1 teaspoon of boric acid and 10 teaspoons of sugar in 2 cups of water. Soak cotton balls in this solution and place in a small dish. Keep the cotton from drying out for continued effectivess by covering the container and replenishing with the boric acid solution when needed.

There is usually no need to tear walls open to eliminate a colony unless repairs are to be made anyway to a faulty or damaged structure. Drilling a 6 to 9 mm (1/4 to 1/8 inch) hole into suspect areas such as walls, sills, joists, underneath sinks, behind appliances or below outside siding can aid in the application of insecticide to the nest if the boric acid solution is not effective. The most effective control is achieved when an insecticide such as an ant and roach killer is placed in the ants' nest. If you cannot locate the nest, but manage to leave insecticide nearby, workers may carry the poison into the nest on their feet. Crack and crevice controls usually take longer (if they work at all) because it takes time for workers to carry enough insecticide into the nest to kill the colony.

Other Ant Species:

There are many other species of ants which are generally beneficial or innocuous when outdoors, but which can become a nuisance indoors. Most of these species can also be treated with a boric acid solution.

Adapted from the University of Maine Cooperative Extension and the Cornell Cooperative Extension, 1999