ENVIRONMENTAL PEST MANAGEMENT
Madison, Wisconsin
Sam Gottlieb

608-277-8828

Carpenter Ants

Carpenter ants are by far, bar-none, the hardest urban pest problem to control. They are rivaled only by the cockroach, and they come in a distant second. 

Damage from carpenter ants can range from none at all, to making the structure unsafe to live in. When structural damage is found, steps should be taken to correct it before the damage continues to weaken the structure. The damage results from the ants removing the wood to expand their living areas.

 

 Photo of damage by Jim Kalisch, UNL Entomology

Damage to Wood by Carpenter Ants
Carpenter ants are the largest ants that we have in the Dane County area. There are several different species of carpenter ants in the area with sizes ranging from 1/8 to 3/4 of an inch. The ants are polymorphic and have several different color schemes ranging from dark brown to black, with a red and black variety also found.

The carpenter ant colony in a structure can live up to 20 years and have as many as 10,000 individuals making up the colony. Winged maters (also called swarms or aletes) appear in 3-5 years after the colony has started. The colony can be of the single or multiple type. The single colony is made up of the queen and all of the workers in one area. The multiple type nest will have the queen and workers around her, but will also have many satellite colonies throughout the structure.

Photo of damage by Jim Kalisch, UNL Entomology

Carpenter Ant Nest in Interior Wall in Cellulose

There are two types of situations the homeowner may run into involving carpenter ants.

  1. Many large black ants coming into the living area during the spring, summer, and fall months. This could be due to several factors. The ants may be living outside and coming in for food/water , or the ants may be living inside the building and foraging inside and outside for food and water.

  2. Ants are seen during cool or cold months, usually anywhere from the middle of October to some time in April. If you are seeing ANY ants during winter months, you can be positive that the colony is inside your home.
A good rule of thumb is that if you can’t find ants outside anywhere but are seeing them inside; the colony is inside the structure.
Photos of damage  by Jim Kalisch, UNL Entomology
 

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