About Carpenter Ants

The Old House Web

antAsthe weather warms, homeowners may panic if they notice large black ants -- mostlikely carpenter ants -- in and around their house, fearing that the home'sstructural timbers are at risk to the pests. But even if you have a carpenterant infestation, you probably have little to worry about, says a Penn Stateexpert.

"Although often blamed for causing damage to wood, carpenter antsusually are little more than a nuisance," says Steven Jacobs, seniorextension associate in entomology in the College of Agricultural Sciences.

"Carpenter ants are somewhat lazy," Jacobs explains. "Theyusually attack wood that's already rotted. If they run into a sound, dry pieceof wood, they generally won't go much farther. But they have been known to causeextensive damage to soft materials, such as insulation board."

Ants vs termites


Carpenter ant workers are wingless, dark brown to black in color and 1/4 to 1/2inch long. The winged reproductives resemble the workers but are up to 3/4 inchlong. The ants' bodies are constricted between the thorax and the abdomen.

Because carpenter ants are social insects that live in colonies and excavatewood, they often are mistaken for termites. However, termite workers are creamywhite and live hidden from view. Winged termite reproductives may resemblecarpenter ants, but termite bodies are not constricted between the thorax andabdomen. Also, termites' antennae are straight with bead-like segments, whereascarpenter ant antennae are elbowed.

In nature, carpenter ants aid in the decomposition of dead, decaying trees byexcavating rotted wood for nesting sites. They eat dead insects and other smallinvertebrates as well as honeydew secreted by aphids and scale insects.

When foraging for food, carpenter ants may find their way inside your house.There, they will feed on meats and foods containing sugar and fat. In somecases, these foraging workers may establish a satellite colony in the house,congregating in existing voids, such as hollow doors or the space between studsin walls.

"In homes, the ants typically do not excavate wood for nests," saysJacobs. "They may tunnel through sound structural timbers, but this haslittle effect on the timber's structural integrity."

Jacobs says to get rid of the ants, the parent and satellite nests must befound and eliminated:

  • Use a flashlight to look for foraging workers at night. "Check basement, attic, garage and building exterior from May through July between the hours of 10 p.m. and 2 a.m.," says Jacobs. "It may be possible to find where they're entering the house or follow them back to their parent colony, which often is located in a tree, log or waste wood within 100 yards of the house. If numerous winged reproductive ants are found at windows, they probably came from an indoor nest."
  • Check areas where the wood may be wet or damp because of poor ventilation, a leaking roof, defective flashing, overflowing or leaking gutters and downspouts, condensation from water pipes, or leaking bathtubs, showers and appliances. "Look for piles of coarse, stringy wood particles, dead insect parts and other debris sifting from cracks in the siding, behind moldings, in the basement and attic and under porches," Jacobs says. "Because carpenter ants don't feed on wood, excavated particles are dumped outside the nest. Satellite colonies within homes sometimes can be located by listening for rustling sounds in walls and ceilings using a stethoscope or inverted water glass."
  • Remove stumps, logs and waste wood within 100 yards of the building. Do not allow vegetation, especially evergreen shrubs and trees, to be in contact with the house.
  • Store firewood away from the house, bringing it into the house only when needed.
  • Keep wooden parts of the house dry by making needed repairs to roofs, flashing, gutters and downspouts. Replace any water-damaged, decaying wood. "Carpenter ants usually won't infest wood that is sound and has a moisture content of less than 15 percent," Jacobs explains.
  • Seal holes through which pipes and wires enter the house.
  • Spraying insecticide along baseboards and around doors and windows may stop ants from foraging in those areas temporarily. But because the nests often are in walls, it won't eliminate the problem. "Commercial baits aren't very effective for carpenter ants," Jacobs says. "Your best bet is to spray around the exterior of the foundation, which provides a barrier to ant movement.Use only products manufactured and approved for this purpose and carefully follow the instructions and precautions on the label," Jacobs warns.

Jacobs says if you prefer to hire professional help to get rid of carpenterants, first get estimates from at least three reputable pest control companies.

-- Information from Penn State College AgriculturalInformation Services

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