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Carpenter Ants Biology and Treatment

posted this on Aug 4, 2016

Carpenter Ants are social ants that live in colonies, primarily in wood. They hollow out wood to build their nests. Their tunneling in wood and foraging for food and water lead to their “pest” status in or around homes. Carpenter ants are an excellent indicator of moisture problems in a building, or other conditions conducive to their infestation, such as rotting wood, that need attention. Homeowners can minimize damage to their houses from carpenter ants by learning how to identify the ants, knowing their nest site preferences, and taking proper preventive and control measures.


Carpenter ants are among the largest ants in the United State. Adults vary in length from about ¼ inch (6mm) for a minor worker, to ½ inch (12 mm) for a major worker, and up to 7/16 inch (18 mm) for winged reproductives. Each colony has one functional, wingless queen, 9/16 inch (20 mm) long.

Winged carpenter ants resemble winged termites. It is vital that they be identified accurately, because control measures differ greatly for the two insect groups.

How to tell ants and termite swarmers apart:

Ants have small, constricted waists; wings of unequal length, with the front pair longer than the hind pair; and antennae bent at right angels about mid-length.

Termite bodies are not narrowed at the middle; their wings are of equal length; and their antennae are rather straight with bead-like segments.


Carpenter ants eat a great variety of both animal and plant foods, including honeydew from aphids, scale insects and other plant-sucking insects, plant juices, fresh fruits, living or dead insects, other small invertebrates, common sweets such as syrup, honey, jelly, sugar and fruit, and most kinds of meat, grease and fat. Unlike termites, they can not digest wood cellulose.

They forage mostly at night from 10 pm to 4 am. Solitary ants seen during the day are usually scouts looking for suitable food sources.

Nesting sites

Carpenter ants normally build their nests in hollow trees, logs, posts, landscaping timbers and wood used in homes and other structures. Unlike termites, they do not feed on wood but merely use it as a place in which to build a nest. They prefer moist or partially decayed wood, frequently entering existing cavities or void areas through cracks and crevices.

Carpenter ants become pests when they nest in one of the voids or damp areas in human construction, or when they forage for food in our houses. Usually, an infestation occurs when all or part of an existing colony moves into a house from outside. Ants can enter when tree branches or utility lines contact a structure; through cracks and crevices around windows and in foundation walls; through ventilation openings in the attic; and through foundation heating or air conditioning ducts.

They usually nest in wood that is very moist or previously damaged by water or termites. This requires the wood to be wet by rain, leaks, condensation or high continuous relative humidity.

Typical locations include:

  • Wood affected by water, seepage from plugged drain gutters, damaged flashing, wood shingle roofs, poorly fitted or damaged siding, improper pitch of porch floors, between the roof and ceiling of flat deck porches, hollow porch posts and columns, or leaking door and window frames;
  • Areas around plumbing in kitchens and bathrooms where water leaks have occurred, soaking the surrounding wood;
  • Wood in contact with soil, such as porch supports, siding and stair risers;
  • Wood in areas of poor ventilation or condensation such as cellars, crawl spaces, attics or under porches;
  • Wood scraps in dirt-filled slab porches;
  • Voids under bathtubs or hot tubs;
  • Hollow wooden doors, hollow ceiling beams, hollow shower and curtain rods;
  • Sill plates and floor joists;
  • Voids under attic insulation or under insulation in crawl spaces; and
  • Voids above windows, doors and bay windows.

During inspection, you may find other wood-infesting insects or damage by them such as Subterranean Termites, Wood-Destroying Beetles, Drywood Termites, Carpenter Bees.

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