Carpenter Ants - Meet the Culprits


Carpenter Ants

Carpenter Ants Carpenter Ant Damage Carpenter Ants


  • Large ants, typically 1/8-5/8-inch long, the queens are often larger
  • There is a single node pedicel (segment between thorax and abdomen)
  • There is a circle of hairs at the tip of the abdomen
  • Overall dull black in color, including antenna and legs
  • Long, yellow hairs closely cover its abdomen
  • Workers range in size from 1/4-to-1/2 inch in length


  • Nest exclusively in wood and in wall voids
  • Main colonies are located outside with satellite colonies inside structures
  • Total colony size for the ant ranges from a few thousand up to 15,000
  • Carpenter ants feed on sugar solutions from honeydew-producing insects
  • Unlike termites, they do not eat the wood as they excavate their nests
  • They feed actively at night from well after sunset through the early morning hours
  • Foraging trails can extend up to 300 feet and, on close inspection, can be seen on the ground as narrow, worn paths
  • They enter structures via gaps and cracks as they forage for food

Roberts Termite and Pest Control, Inc. focuses their carpenter ant inspections on the following problem areas:

  • All satellite colonies within a structure. In established infestations, a number of satellite colonies may be involved. Baiting programs are successful in eliminating satellite colonies; however, spray and dust programs may miss one or more satellite colonies, which will require additional time in inspection and perhaps in treatment.
  • Garages and out buildings. Homeowners see ants inside the structure and request that management be directed at the house. Inspections should include all buildings on the property with as much attention given to these outbuildings and garages as to the home. Although firewood is recognized as a conducive condition, other lumber should also be considered. Grooved siding, plywood, lumber, and ornamental driftwood that are stacked in attics or in the rafter of these outbuildings may be the source of the ants that have invaded the living space.
  • Large trees in landscaping. Healthy trees may support a main colony and be the source of satellite colonies within a structure. When trees are planted close to a structure, roots may provide an avenue for the ants to reach the foundation with very little exposure.
  • Fences. Wooden fences around yards often contact the side of the structure. Fences provide mass transit from one area to another and ants may be trailing from a colony on adjacent property that does not belong to property being treated. Also, we note where vegetation touches the fence as the ants may be trailing from these areas.


Carpenter ant control is ideally accomplished if the main nest and all the satellite nests can be located. Preventative measures include: keeping vegetation from contacting roof or exterior walls and foundations; preventing wood-soil contact; ventilating to prevent moisture accumulation in attic and crawlspace; stacking firewood and lumber off the ground away from buildings; repairing leaks in roofs and gutters; and pretreating before and during construction of new buildings. Treatment of carpenter ants includes removing as many of the above conducive conditions as possible.

A number of treatment options are available. Application of a dust formulation to wall voids effectively eliminates satellite colonies living in these areas. A perimeter spray applied to the lower edge of the exterior siding, around window and door frames and on the sill plate if a crawlspace is present accompanies this type of treatment. Baiting for carpenter ants is another option to be used when the ants are foraging. Initial baiting requires period of several days to a week to determine if the ants are feeding on the bait. To reduce the length of time and determine which bait is acceptable, several baits may be offered. Perimeter sprays are suggested as a preventive measure in areas where there is a high population of carpenter ants or the main colony was not located.


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