Carpenter ants are important in the balance of nature because they burrow and nest in dead trees and enhance decay of the wood. They achieve pest status when a colony invades and damages the integrity of the wood within a house. This fact sheet will explain how the biology and behavior of carpenter ants relate to control strategies when a homeowner is faced with this problem.

Description and Habits: The black carpenter ant, Camponotus pennsylvanicus, is the most common carpenter ant species in Nebraska. Foraging workers are 1/4 inch to 5/8 inch and black in color. Another species, the rust-colored carpenter ant, Camponotus ferrugineus, is a bit smaller and has a reddish-orange thorax with a black head and abdomen. The most diagnostic characteristic of all carpenter ants is they have a one-segmented pedicel (the segment between the thorax and the abdomen). The profile of the thorax is evenly rounded and not bumpy.

Most carpenter ant workers are polymorphic—which means they are different sizes. Entomologist refer to larger workers as "major" workers and the smaller workers as "minor" workers. Each colony has at least one "queen," the reproductive member that produces all additional members of the colony. There may be more than one queen in a colony.

When a colony gets very large (six- to ten-years-old and has more than 2000 workers), it may produce winged reproductives, called swarmers. They are often produced during the summertime and may overwinter in the colony. In Nebraska, we have people reporting swarms of the rusty-colored carpenter ants during periods of warmer weather from February to April. The black carpenter ants swarm a bit later and are more commonly observed from March to June, but we have seen swarming of both species during most warmer months. The males often emerge first and are smaller than the females.

After mating, a single queen seeks out a suitable nesting site and lays only a few eggs that hatch into maggot-like larvae. She cares for the larvae that become the colony's first workers, forage for food, and feed the young while the queen continues laying eggs.

The diet of carpenter ants is quite varied and includes living and dead insects, honeydew from aphids, sweets, meat, and fats. They do not eat wood. Workers leave the colony in late afternoon or early evening, forage during the night, and return to the colony in the early morning hours.

Carpenter ants carry food back to the nest intact or ingested and later feed it to non-foraging members in the nest. These ants may forage up to 100 yards from the nest to search for food. Carpenter ants may become pests in houses by foraging for food. The greatest concern, however, is they may cause serious damage to wood in the structure. Unlike termites, they do not feed upon wood, but merely use it as a place to nest.

Carpenter ants construct their nests in hollow trees, logs, posts, landscaping timbers, and wood used in homes and other structures. These ants prefer to infest wood that is moist and rotting, but wood that has been wet previously, may be soft enough to allow carpenter ants to hollow it out and produce a colony. Certain parts of a house such as: Around and under windows, roof eaves, decks, and porches are more likely to be infested by carpenter ants. Refer to the diagram on the back for the most common problem areas of a home.

Carpenter ants will use an old abandoned nest or wood that has been "hollowed out" by termites. Nests may be located in hollow doors or small void areas produced during construction.

Carpenter ants may move from decaying portions of the wood into sound lumber in the process of enlarging the nest. They cut galleries with the grain following the softer parts of the wood. The ants leave harder parts of the wood as walls separating the tunnels and cut openings in these walls to allow access between tunnels. Access to the outside may be through natural openings, or the ants may cut openings where none exist naturally.

Carpenter ants keep occupied galleries clean. They remove wood in the form of a coarse sawdust-like material, which they push from the nest. This often results in a cone-shaped pile accumulating just below the nest entrance hole. This pile may include, in addition to the wood fragments, other debris from the nest, including bits of soil, dead ants, parts of insects and remnants of other food they ate.