Carpenter ants are among the largest ants in Minnesota. There are several species of carpenter ants that may be found infesting homes and other buildings. Normally workers are black, or red and black, in color; and range in size from 3/8 to ½ inch. Winged queen ants may be as large as one inch. However, size is not a reliable characteristic for identifying carpenter ants. In Minnesota, there is one species with workers no larger than 3/16 inch.
The best method to distinguish carpenter ants from other ants is by the following characteristics: 1) a waist with one node (petiole) and 2) a thorax with an evenly rounded upper surface.
There are other ants that appear similar and are occasionally mistaken for carpenter ants. They may have one or two nodes. However, they can be distinguished from carpenter ants by the uneven profile of their thorax.
Behavior, Diet & Habits
Carpenter ants feed on sources of protein and sugar. Outdoors, carpenter ants feed on living and dead insects. They are also very attracted to honeydew, a sweet liquid produced by aphids and scale insects. Aphids and scales feed on trees, shrubs, and other plants. Indoors, carpenter ants feed on meats and pet food, as well as syrup, honey, sugar, jelly, and other sweets. Carpenter ants DO NOT eat wood. They remove wood as they create galleries and tunnels for nesting.
Carpenter ants also interact with our houses when they travel back and forth between their main nest, which must be persistently damp and thus is usually outdoors, and their satellite nests, which may be on the outside surfaces of houses (porches, decks, etc.) or may be in walls, doors or other hollow spaces indoors.
The queen lays 9 to 16 eggs the first year and may live up to 25 years. Eggs complete their life cycle in about 6 to 12 weeks.
Signs of a Carpenter Ant Infestation
Carpenter ants damage wood by excavating and creating galleries and tunnels for their nest. These areas are clean (do not contain sawdust or other debris), and are smooth, with a well-sanded appearance.
The damage to wood structures is variable. The longer a colony is present in a structure, the greater the damage that can be done. Structural wood can be weakened when carpenter ant damage is severe.
It is common to find carpenter ants in homes during spring. It is important to try to determine whether the ants are coming from an outdoor primary nests or an indoor area, although this can be difficult. Their presence is not sufficient evidence to conclude that there is a nest in your home. You may be able to make a more accurate determination based on when you first see carpenter ants. If you find carpenter ants in your home during late winter or early spring, that suggests the ants are coming from a nest in the building. However, if you see activity later in the year, it may be less clear if the nest is in the building.
You may also see carpenter ant swarms during spring. Carpenter ants produce large numbers of queens and males during late summer. They emerge from nests the following spring (this can also happen during late winter) for their nuptial flights. After mating, queens search for suitable sites to begin new nests. Once they land, their wings break off and each queen attempts to construct a new nest.
When carpenter ants nest indoors, mating swarms may become trapped inside. Finding large numbers of winged ants indoors is a sure sign that an indoor nest exists and may give the approximate location of the colony.
The workers may be observed foraging for food. Swarmers usually are produced when a colony matures and is ready to form new colonies. These winged individuals often indicate a well-established colony. An additional sign of carpenter ant activity is the debris they produce from tunneling in the wood. Rough wood shavings mixed with parts of dead ants from the colony indicate carpenter ant nesting activity. A final sign may be the “rustling” sound sometimes heard as the ants go about their activity in the home’s wood.
In natural environments, carpenter ants dwell in both dead and living trees, stumps and rotting logs. However, they may also establish their nests inside of homes and buildings where wood is found. Carpenter ants prefer to establish nests in areas where wood has been exposed to severe moisture.
Carpenter ants build two types of nests: parent colonies and satellite colonies. Parent colonies consist of a queen, her brood and workers. Satellite colonies consist of workers, older larvae and pupae. Workers create satellite colonies when the parent colony lacks sufficient space or when there is a suitable supply of food or water. There may be several satellite colonies associated with a parent colony.
Carpenter Ant Treatment
If treated early, carpenter ants are seldom responsible for serious structural damage to houses and buildings. However, these ants could cause extreme damage if they continue undiscovered for an extended period. All moisture conditions that the ants found conducive must be corrected. Thus, it is best to contact a pest control professional in the event of an infestation. It is advisable to seek professional help in containing carpenter ant infestations, as incorrect procedures may allow the colony to rebound when surviving members resume their burrowing and foraging.