Carpenter Ant

Carpenter Ant

services4Carpenter ants are one of the most valuable insects we have on earth. They chew up tons of wood and turn it into fine sawdust that rots and provides compost for new growth. Because they enter manmade structures they are considered the most destructive common insect pest we have in Canada.

Two common species of carpenter ants found in Canada (there are others):

  1. Modoc: all black (legs may have a rusty red colour); one queen in parent nest.
  2. Vicinus: black head, rusty red thorax (mid-section) and black abdomen (tail section); multiple queens in parent nest.


Five Sizes: Carpenter ants can be as small as one quarter inch or as large as three quarters of an inch. All sizes can be found in one nest.

Most carpenter ant species establish their initial nest in decayed wood, but once established, the ants extend their tunneling into sound wood and can do considerable damage to a structure.

Identification and Life Cycle

These species commonly nest in standing trees (living or dead), in stumps, or in logs on the forest floor. Since many houses around here are being built in forested areas, well-established, vigorous colonies are readily available in the immediate vicinity to attack these dwellings. This is especially true when the homeowner insists that the home be built with a minimal removal of trees.

Carpenter ants typically have a parent colony in outside nesting areas, such as live or dead trees, stumps, logs or decorative landscape wood. When the colony grows larger and needs room to expand satellite colonies are established. These satellite colonies often develop in nearby structures presumably because they offer warmth and protection.

Only the parent colony contains the queen(s), young larvae and workers, while the satellite nest contains the mature larvae, pupae, workers, and/or winged reproductives. Ants move back and forth from parent nest to satellite nest but just a few (less than 10%) will be visible foraging for food.

Sometimes they can be seen moving mature larvae (white and grub-like) or pupae (papery cocoons).


Ants are generally active along ant trails from April to mid-October. These trails follow natural contours and lines of least resistance and also frequently cut across lawns. Traffic on these trails may be noticeable during the day, but peak traffic occurs after sunset and continues throughout the night.

The parent colony is often located in a tree stump, stacked wood within 100 metres of the house or wood and stumps buried in the yard when the house was constructed. Decorative wood landscape ties brought in to enhance the beauty of a yard or driveway may also be the source of a parent colony. The colony does not produce reproductives (winged males and queens) until it is from three to six years old and contains about 2,000 workers. The natural food for these ants consists of insects and other arthropods and sweet exudates from aphids and insects. They are also attracted to other sweet material such as decaying fruits.

Reproductive carpenter ants (winged males and females) leave the nest as early as January if the nest is in a heated structure. Those living outside in logs and stumps will not swarm until about early May. The fertilized queens must then find wet wood to establish a new nest, and the cycle starts over again. The new queen could live 15 years or more and lay 70,000 fertilized eggs.


Getting Rid of Carpenter Ants

Finding carpenter ant nests requires a lot of time and patience, a job that is best left up to the professional. With years of experience, a professional will know where these nests are likely to be and will look for evidence of frass (the junk thrown out of nests). This is often caught up in spider webs in attics, crawl spaces, basements under decks and around the exterior perimeter under the soffits and below the siding. Sometimes the frass excavated by the ants from the structure will be noticeable, but not always.

Following ants outside the nest is the best indication of its location, but ants will often follow channels hidden from the hot sun, rain and your vision. Less than 10% of the population will ever leave the nests, so at times there are very few to follow. Knowing whether the ant you are following is heading for food, or has already eaten and is heading back to the nest is an indicator that some very experienced professionals are capable of seeing.

Listen for them. If your hearing is good and the home is very quiet, you may be able to hear the rustling and chewing noise they make. A medical stethoscope is useful but the sound of a refrigerator or even a clock can confuse the inexperienced ear.

pest29How to Find the Main Nests

In some locations it would be impossible to find all the main nests among the trees, logs, stumps, buried wood and roots. Even if these nests are found, removing them can be a monumental task. All satellite nests remain in contact with the main nest. Workers can be seen carrying mature larvae from the overcrowded queen’s home to new or established satellites of the colony. If you find the main nest, try to remove it physically. If you put toxic products into it, they may leach into the ground water and contaminate water supplies or fish habitat some distance away.

If you cannot remove the nest, try to eliminate any favorable conditions that encourage them to move toward the home. Tree branches, fences, garden hoses, structural wood touching the soil, landscape ties and utility wires all provide an easy route for them to follow. A very fine dusting of diatomaceous earth around the perimeter base of the home will discourage all insects from crossing it to gain entry. This is short-term and should be repeated frequently in the spring, summer and fall.