The sight of large, black Carpenter ants scurrying across the floor is a worrying sight for home owners because it might mean that somewhere in the house insects are chewing on wood.

Ten species of Carpenter ants are native to B.C. They are medium to large ants, 6-12 mm long (3/8-1/2 inch); the flying queen ants may be nearly 2 cm long (7/8 inch).

Ants can be distinguished from termites by their narrow wasp-waist and antennae that have an elbow bend in the middle. Termites aren't indented at the waist and their antennae are straight.

Carpenter ants are one of the most beneficial predators in the forest ecosystem. They feed on small insects and honeydew and they scavenge dead insects and decaying material. They are particularly prolific in the moderate climate and high humidity of coastal British Columbia. For brief periods in the spring and early summer the winged Carpenter ants swarm into the air on mating flights. The queens are easy to see as they settle, shed their wings and search for crevices in decaying wood to begin their nest. Very few of them will find an ideal site (usually outdoors) and their presence does not mean that the house is infested.

Carpenter ants make two types of nests. If the queen finds moist, decaying wood, she tunnels into it to begin the main nest. This site must be permanently moist or the eggs and younger larvae cannot survive. Old nests can contain thousands of ants, but it takes several years for a new nest to build up to a few hundred individuals. Main nests are usually outdoors in rotting stumps, trees or in decaying landscape timbers. They can become established in houses where wood in the structure has begun to decay. Although Carpenter ants do not eat wood, they do tunnel into it to make their galleries. Once they establish a nest in damp wood they will eventually damage the structure by tunnel ling from the decaying wood into the sound wood. Carpenter ants also make satellite nests where they care for the older larvae and pupae that tolerate drier conditions. These nests are often in wall voids and eaves, ceilings or under insulation in attics or crawl spaces. Most nests in houses are satellite nests that maintain communication with the main nest.

The two ways to deal with Carpenter ants are:

1. Prevent them from entering in the first place, and
2. Remove infestations that have become established.

The best protection from damaging infestations is to maintain dry conditions with proper construction and maintenance of the house.

• Repair wood damaged by moisture and ventilate damp areas.
• Clean gutters to avoid clogging, which leads to water damage to siding or roof.
• Store firewood on raised platforms, well away from house.
• Prune trees so branches don't touch the house.
• Remove all nearby rotted stumps or logs. Check for rotting landscaping wood.
• Ensure that wood of the siding or structure isn't in contact with soil at any point around the house foundation.

The key to controlling ants is finding the main nest, where the queen is laying eggs. This requires thorough inspections and an effort to follow foraging ants back to their nest. If you see more than 10-12 ants in your house in an evening, it is worth investigating whether their nest is in the house or whether they are on a foraging expedition from outdoors. First, make sure the insects in question are Carpenter ants.

If in doubt, catch some of the largest ones and have them identified. Follow some of the ants until they lead you, back to the nest. Sometimes Carpenter ants are interested in sweet food in the early spring and you may be able to attract some to jam or honey and then follow them homeward. They use the same trails over and over and are most active at night.

During the inspection of the house, thoroughly check the crawl spaces and attics as well as under porches. Look for signs of nesting activity, such as mounds of loose shavings or sawdust beneath a crack in a wall or eave space. Also, listen for rustling sounds in the walls (use a rolled up paper tube to amplify the noise). Carpenter ants particularly like to nest in wall cavities, under siding, between floors and where wood is in contact with soil.

Satellite nests can also be near roof gutters, down spouts and in the ceiling. The control measures given above may not eliminate established ant infestations in high risk houses, such as those surrounded by woods, those on earthen crawl spaces or with decaying timbers in the foundation. In this case, or if you are unable to make the necessary inspections, it is advisable to call a licensed professional pest control service to locate the problem. Choose a service that will conduct a thorough inspection for the main nests and that is willing to discuss with you, in detail, the advantages and disadvantages of various treatments. To prevent the problem from recurring after treatment, replace or repair any damaged timbers and correct moisture problems. If you choose to have the pest control service apply pesticides to the perimeter of the house to prevent future Carpenter ant invasions, it is important to know that the only areas necessary to treat are along the top of the sill from inside the crawl space, and under the bottom edge of the siding on the exterior. Carpenter ants make nests in wood, often the structural wood of your walls. They do not eat the wood, they excavate it. The damage they do is slow but steady. Often the most annoying part of having a carpenter ant problem is the fact that during the winter months, they are meant to be dormant, however the combination of a sunny day and the furnace heating the walls will convince some ants that it’s spring, and they will visit your kitchen, starving. No real treatment can be undertaken at this time, but it is definite evidence of a nest within your walls. That is when you start planning for spring treatment, including the following points:

• Ground cover (even around fences) should be eliminated wherever possible. Carpenter ants feed on this sort of vegetation; also, ground cover hides the path of the ants (between main and satellite nests) from the pest control technician’s eyes. Where ground cover is present, finding a main nest (often in a dead tree stump and may be up to two blocks away) is almost impossible.
• All vegetation in contact with the building and fence should be trimmed back, for the reasons listed above as well as to ensure the effectiveness of an annual outside perimeter spray.
• If ants show up inside between Fall and May, we recommend the use of borax-based liquid ant bait (available at Safeway, London Drugs, etc.) laid out on masking tape, in very small drops, wherever it will not be stepped in by kids or pets (it’s sticky). The ant bait will kill ants, but not the nest, which is still mostly dormant. Treatment during the winter is virtually impossible and is totally useless. Please do not spray anything down any holes you may find, as it can cause the nest to move, with more wood damage ensuing. These winter visits will cease of their own accord.
• At minimum, your treatment next spring and summer should include a perimeter spray (after the vegetation has been cut back) Other, more extensive treatment may be undertaken if useful evidence presents itself.

Above all, be concerned but don’t panic. This is a very common problem and no-one’s house has ever fallen down because of it.

ENTRYWAY for ANTS A. Fence joined to House B. Plumbing outlets C. Lower edge of siding D. Edges of chimney bricks E. Vents F. Gutters G. Window casings H. Door frames I. Vegetation touching house J. Overhead wires

POSSIBLE sites of MAIN NESTS 1. Wood in contact with soil 2. Woodpiles 3. Decaying tree roots 4. Heartwood of live trees 5. Rotting stumps