Carpenter ants are among the largest ants. 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.

A colony of ants are divided into different castes, workers, queens, and males. Some ants, including carpenter ants, have different sized workers which help the nest with a range of jobs from food collecting to nest defense. 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.

Unlike termites, they only nest in wood and do not eat it. Outdoors, they commonly nest in hollow trees and stumps. Finding them indoors during the summer does not necessarily mean they are nesting in your house, they may just be coming in from outside. However, the presence of carpenter ants in homes during the winter months, when it is too cold outside for ants to be active, is a very strong indication a colony of carpenter ants exists inside the building. When they do nest indoors, they prefer an enclosed space that remains wet or damp, more or less, on a permanent basis. Carpenter ants are attracted to excessive moisture conditions around windows, doors, showers, bathtubs, dishwashers, leaky pipes and drains, and under leaky roof shingles or roof vents. They have also been found in dry areas such as hollow-core doors and false beams, and blueboard foam insulation.

Prevention Tips

Eliminate high moisture conditions that are attractive to them.

Replace any moisture-damaged wood.

Be careful to prevent moisture in wood or lumber that is stored in a garage or near the house.

Store firewood as far away from buildings as possible.

Remove tree and shrub stumps and roots.

Trim branches that overhang or touch the home.