Extension Logo
Extension Logo
University of Minnesota Extension
extension.umn.edu

Carpenter ants

Quick facts

  • Carpenter ants are very common in Minnesota.
  • They can potentially damage homes and other wooden structures.
  • The best method for controlling carpenter ants is to deliver insecticide into their nest.
  • Because controlling carpenter ants is complex, it's best to hire a pest management professional (pest control technician) to eliminate nests.

Identifying carpenter ants

Carpenter ants are among the largest ants in Minnesota. There are several species that may be found infesting homes and other buildings. 

How to recognize carpenter ants:

  • They have a waist with one node (petiole) and a thorax (area behind the head) that is evenly rounded when viewed from the side.
  • Workers are black or red and black.
  • Workers usually range in size from 3/8 to 1/2 inch long; one species is only 3/16 inch.
  • Even carpenter ant workers of the same species vary in size (major and minor workers).
  • Queens and males are larger than workers and have wings. Queens lose their wings once they start a new nest.
  • Queens may be as large as one inch long.

Other ants can be mistaken for carpenter ants. They have one or two nodes and an uneven thorax when viewed in profile. They usually do not infest wood.

Correct identification of the ants is important for control strategies to work effectively.

Left column: winged female (top), winged male. Right column: workers of varying sizes.
Carpenter worker ant
Non-carpenter ant worker with an unevenly shaped thorax and a two-segmented petiole

Ant or termite?

Carpenter ants have dark-colored bodies, narrow waists, elbowed (bent) antennae and hind wings that are shorter than front wings (if wings are present).

Termites are very uncommon in Minnesota.

  • Workers are light-colored, have broad waists and straight antennae.
  • They avoid light and are rarely seen outside of their colony.
  • Winged termites, queens and kings, are dark-colored and have wings of equal length. 
Winged carpenter ant
Winged carpenter ants
Winged termite
Winged termite

Biology

 | 

Damage

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. Generally, damage occurs slowly, often taking years to occur.

Prevention and control

 | 

Authors: Jeffrey Hahn, former Extension entomologist and Stephen Kells, Extension entomologist

Reviewed in 2020

Share this page:

© 2021 Regents of the University of Minnesota. All rights reserved. The University of Minnesota is an equal opportunity educator and employer.