Carpenter Ant Control


Carpenter ant problems vary. This is partly due to biology. More than 20 species of carpenter ants are structural pests in North America. It is also partly due to climate. Cool, wet areas of the Pacific Northwest and New England have large carpenter ant problems. Finally, it is partly due to construction styles. Houses nestled in dense woods, or those with bay windows, leaky skylights, foam insulation or cedar shake shingles have a risk of attack. Carpenter ants may have more than one nest. In many areas of the country, multiple nests are the rule rather than the exception. Large colonies often consist of a parent nest and one or two more satellite nests (Up to ten have been reported!) The parent colony always contains the queen and small larvae; the satellite nests contain larger larvae and pupae. Workers occur in both, moving from one nest to another over well-defined trails. A mature colony contains anywhere from a few thousand up to more than 50,000 workers, depending on the species and conditions at the site. The ants often return to the same nest sites year-after-year.

Moisture and carpenter ants go together. Carpenter ant queens prefer to nest in moist wood. High moisture levels appear necessary for egg hatching and early larval development, so parent nests are usually located in damp or wet sites. In some areas of the country, carpenter ant nests in buildings are nearly always associated with high moisture. Potential places include:

  • In wood, voids or insulation wet from leaky roofs
  • In roofs kept wet in winter by ice dams
  • Under leaky shower pans, tubs, and toilets
  • In wet crawlspaces
  • Under plumbing leaks, leaky dishwashers and washing machines
  • In and around damaged window and door frames, deteriorating chimneys and water-damaged porch supports

However, an indoor nest site can be dry. Satellite nests are often located in sites that are warmer and drier than parent nests. Worker ants may excavate satellite nests in completely dry wood or in panel insulation, or they may simply move a satellite nest “lock, stock and barrel” into a dry void or hollow door. Carpenter ants have even been known to move a satellite colony into a dry void in a new house before construction was completed.

The ants inside may be from a nest outside. Outdoor nest sites include rotting tree stumps, hollow trees, firewood (particularly old, rotting wood), railroad ties, fence posts, decks, sheds and under flagstones. Carpenter ants may be foraging for food by following trails from their outdoor nest into the house.

Carpenter ants are active at night. Carpenter ants are most active at night between the hours of 10:00 P.M. and 2:00 A.M.

Carpenter ants come in many varieties. Carpenter ants can be different colors - tan, red, black. And many sizes - most workers are between 1/4” and 1/2”. Contrary to popular belief, carpenter ants actually eat the same thing as you and I, although they show a preference for sweets. During the summer they will feed on other insects.

Carpenter ant activity changes with the season. Where winters are cold, carpenter ants go into diapause. There is little activity from October to February. Swarmers emerge from the mature colonies when the weather turns warm in spring. In most of the United States, this is sometime between March and June. This is also peak foraging time for the workers as they gather food for the developing larvae. There is a second, lesser period of foraging activity in July.