All About Ants

Types of Ants :: Carpenter Ants :: Printer-Friendly Version

Ant Origin & Distribution
There are as many as 50 species of carpenter ants in the United States and Canada. Most are native and depending on the species, may be found from sea level to elevations as high as 9,000 feet. While all carpenter ants are "at home" in natural environments, about 24 of the 50 species are considered to be structure invading pest ants. Others are considered only nuisance pests, occasionally infesting structures. Carpenter ants do not eat wood but rather excavate it to form galleries for nesting.

The more common structure infesting carpenter ant species include:

Eastern United States

• Camponotus pennsylvanicus (C. pennsylvanicus): Commonly known as the Black Carpenter Ant, this species nests exclusively in wood and is the principal structural pest carpenter ant of the eastern and central United States.

• C. floridanus and C. tortuganus: C. floridanus, known as the Florida Carpenter Ant, is common throughout Florida with its range extending into other southeastern states. C. tortuganus is found in southern Florida where it is considered a common household pest. Both species do little excavation or structural damage to sound wood, but nest in already damaged wood and existing structural voids. They can be seen foraging in and around structures.

• C. novaboracensis and C. herculeanus: C. novaboracensis, also known as the New York Carpenter Ant, is found throughout the northern United States but is more common east of the Dakotas. It is also found in many western states extending south into New Mexico. Although considered a common structural pest in certain regions, it may be considered only a nuisance pest in others. C. herculeanus, although rare in North Dakota and non-forested regions, can be found in northeastern states and in many western states including Alaska. It is considered the second most common structure infesting species in Minnesota.

• C. modoc and C. vicinus: In western states, two species that commonly infest structures are C. modoc, also known as the Western Black Carpenter Ant, and C. vicinus. C. modoc is the principle structural pest in the western United States and C. vicinus, is second only to C. modoc as a structural pest in Washington.

Ant Identification
Most carpenter ant species are polymorphic. This means that workers in a colony may vary in size. For example, workers of the common Black Carpenter Ant species (C. pennsylvanicus) range in size from 1/4" to 1/2" in length. In contrast, workers of C. herculeanus, range in size from 1/8" to 1/3" in length. Coloration varies by species. Some are primarily black or brown while others have variations of black and red or black and yellow brown. Below are size range and coloration of workers for the more common carpenter ant pest species, although size and coloration of carpenter ant workers are not considered to be accurate identification characteristics. For accurate identification of ants, homeowners should rely on a trained professional using a scientific key and microscope.

C. pennsylvanicus (Black Carpenter Ant): Overall dull black in color with pale yellow or light hairs. Workers range in size from 1/4" to 1/2" in length.

C. floridanus (Florida Carpenter Ant): Head, thorax and petiole are reddish to orange with a black gaster. Workers range in size from 1/5" to1/2" in length.

C. tortuganus: Similar to C. floridanus but paler with less contrast in color. Workers range in size from 1/4" to 3/8" in length.

C. novaboracensis (New York Carpenter Ant): Brownish black head and gaster and red to yellowish red thorax. Workers range in size from 3/16" to 3/8" in length.

C. herculeanus: Body mostly black with rear of thorax, petiole and legs dark red. Workers range in size from 1/8" to 1/3" in length.

C. modoc (western Black Carpenter Ant): Similar in coloration to C. pennsylvanicus (Black Carpenter Ant) except legs are dark reddish in color. Workers range in size from 1/5" to 1/2" in length.

C. vicinus: Variable in color with most common variation having a black head, gaster and legs and a red thorax. Workers range in size from 1/4" to 1/2" in length.

Ant Biology
Mature carpenter ant colonies produce male and female swarmers (ants with wings) that spend their winters in nests and take flight in the spring. The timing and numbers of flights within a season varies by species. New colonies are formed when a fertilized queen, fresh from her mating flight, finds a suitable site to excavate a small nest chamber in which she begins laying eggs. This site may be on the ground under wood debris, fallen logs or landscape timbers, or under loose bark, in decayed wood or cavities in trees (living or dead). New nests can also occur within structures in wood contacting the ground or in moisture-damaged wood. With some exceptions, most carpenter ant species have one queen per colony.

Once the first workers hatch from eggs, they begin the tasks of nest excavation, foraging for food and caring for new brood and the queen. The nest will grow slowly over several years, expanding into surrounding dead and damaged wood and it may take as many as six to 10 years before new swarmers are produced.

As a colony develops, satellite nests are produced which are connected to the parent nest by trails traveled by workers. The satellite nests contain workers, older brood (no eggs or young larvae) and sometimes swarmers, but the queen remains in the parent nest. Satellite nests are more apt to be found in structures than are parent nests, comprising as much as 75 percent of structural infestations. They are often found under insulation and in wall voids, attics or crawl spaces. The numbers of satellite nests a parent colony may have will vary by species. Some species may only have a few, if any, while others, such as C. modoc may have as many as 20. Numerous satellite nests may make carpenter ant control difficult. The population (numbers of workers) of carpenter ant colonies varies by species. Although, as a general rule, an average size colony for most species may be 3,000 to 6,000 workers, some species (C. modoc and C. vicinus) can have up to 100,000 workers. As with all ants, when conditions become unfavorable, workers may move a colony to a more suitable site.

Ant Habits
As a general rule, carpenter ant foraging is most active at night although some species may forage in daylight hours as well. In their search for needed resources, carpenter ants will develop trails linking their nests and feeding sites. These trails may even be used year after year and can be hundreds of feet long. Depending on the species, trails may be above or below ground, and surface trails may sometimes be covered with debris creating a protective canopy. Carpenter ants will use guidelines when trailing, as do many pest ants. Tree branches and utility wires are commonly used to access structures, and trails can be seen on edges of lawns, pavement, foundations, landscape timbers and even garden hoses. Indoors, carpenter ants may be seen trailing along edges of cabinets, floors and furniture.

Other signs of a carpenter ant infestation can be small piles of "sawdust" which are produced from their nest excavations. Usually these piles are near a nest. They will also contain bits of dead ants and other insects. If bits of insulative foam are seen in the piles, it may be a sign of nests in structural foam elements. In addition to nesting in wood, carpenter ant nests can also be found in structural voids such as under insulation in attics, basements and crawlspaces, and sometimes in odd places such as ceiling light fixtures, under and behind dish washers and inside boxes in attics and basements.

If left undisturbed, damage to wood by carpenter ants can be extensive depending on the species and the degree of the infestation. They are the principle insect pest causing damage to structures in the northern states, and in the Pacific Northwest and northeastern United States, they can be as destructive as termites. In many cases though, damage may be minor, primarily due to localized satellite nests in structural timbers and voids. Their galleries in wood have a smooth sandpapered appearance and will be free of any mud, pellets or powdered frass. If mud, pellets or powdered frass are present in the galleries, the damage is likely due to other wood damaging insects like termites or beetles.

Carpenter ants will feed on a wide variety of foods including their natural food sources of honeydew, plant secretions and insects. In and around structures they may feed on many different kinds of food including sweets such as candy, syrup, soda pop, fruits, pastries and pet food. Preference to foods may change over the course of a season and may result in poor control with bait-type insecticides if the food source is not attractive to the ants at a given time.

Ant Control
If you think you might have a carpenter ant infestation in your home, it's imperative that you contact a certified and licensed pest control professional to inspect the situation and confirm identification. A trained professional is needed to understand the complex nature of this pest and specific control methods that may be needed. Experts will advise against do-it-yourself options, as it is much more efficient and cost-effective to have a trained set of eyes identify the correct ant species and recommend effective treatment options specific to an individual infestation. Improper do-it-yourself options may result in killing a few ants, while the rest of the colony simply relocates to other areas around and inside the structure.