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Be Prepared For A Home Invasion

The first step to dealing with an infestation is to identify the intruder. Termites are 10 times as destructive as carpenter ants, but termites are far less likely to be the culprits as they are not native to the Prairies. The distinctions in appearance between carpenter and other species of ant are subtle, and ants in wood aren’t necessarily carpenter ants as several other species will move into already damaged wood. Carpenter ants are the largest. They have a thin waist with one node (bump) and a thorax (midsection between head and waist) with an evenly rounded upper surface. Other ants have an uneven appearance to their thorax and may have one or two nodes. To see illustrations, go to DK1015.html.

There are two species: Modoc (all black, although legs may be rusty red) and Vicinus (black head, rusty-red thorax and black abdomen). The largest are the queen and the major workers which can be as long as three-quarters inch (1.8 cm). Reproductive winged males and minor workers can be as small as one-quarter inch (. 6 cm). They are dormant in winter and the queen, winged reproductives and workers can survive up to six months with no food or water, even when the nest is not located in a warm area.


Once identified you need to locate the nest(s). Do not use an insecticide before this, as it will interfere with your search by disrupting scent trails set down by the ants. Trails follow the natural contours of landscape with the least resistance so can disappear under boards, sidewalks and such, which hampers detection. If undisturbed, ants follow the same path between nest and food source. They search for openings (cracks, holes, gaps, vents) and can also enter a home on firewood. The best time to locate trails is between 10 p. m. and 2 a. m. from April to October, and as they cannot see red light, place red cellophane or plastic over a flashlight lens when searching. Put out cardboard smeared liberally with syrup or honey which will encourage a steady stream of ants carrying food back to the nest, making detection easier.

Nests are formed in any void: hollow doors, walls, ceilings, subfloors, attics, crawl spaces, and common sites are around doors, windows, chimneys or any wood exposed to the elements. Sightings inside are relatively rare, but are usually in bathrooms or laundry rooms. They are good at detecting dampness and are particularly prone to entering homes during drought periods.

Carpenter ants don’t eat the wood they chew but instead create galleries for nests and tunnels for travel. Workers pile “frass” made of sawdust, dead insect parts and other debris, outside of nest openings. A soft rustling noise that resembles the sound of light rainfall in walls, ceilings or floors can indicate their presence, but you need a very quiet house to hear this. Even the noise of a running fridge may mask it. The ants travel along wires, pipes, and through their tunnels, destroying insulation so that an exterior wall feels cold.


Hiring a professional exterminator can get expensive and the need for three visits is common. The first is to locate the nest(s), the second to treat, and the third to make sure the treatment was successful. You can reduce the bill by knowing exactly what pest you are up against and locating the nest(s) yourself. Ask questions before hiring. Is there a charge for each visit or does the quoted estimate represent a package of services? What is their policy regarding reinfestation after treatment? Will there be an additional charge if they must return before a certain time? The company should provide information on how to prevent a reoccurrence.

If you decide to do it yourself, carefully read and follow all pesticide instructions. Bait is only useful if ants find it, so first monitor their habits. Gel-style bait is good for placing along your home’s lines of entry – granular bait can go in areas where you know ants are living or travelling. They must eat the bait, return to the nest and regurgitate the poison for other colony members to eat. A delayed toxicant is crucial as it allows this process to spread throughout the colony. Baits vary as to longevity when exposed to the elements and need reapplying anywhere from days to months.

Do not use other faster-acting sprays or dusts. You kill only the ants that leave the nest and this may cause the colony to move, resulting in more damage and requiring more time to locate the new nest. For elimination

purposes, spraying or dusting outside the nest is rarely benefi cial as very little is carried back to the nest. If you unintentionally expose a nest due to renovations, spray directly and heavily with an aerosol product. Opening a nest results in workers immediately attempting relocation, so do not rip apart a suspect area. Treat it first and check to see if your treatment was effective. Only open the area to see if structural repairs are needed once you are certain the ants are dead. Over-the-counter dusts sold at hardware stores are often ineffective on carpenter ants unless injected right into the nest and this is difficult to do without professional equipment. Any spraying or dusting to prevent a reinfestation should wait until you are sure you have eliminated all nests.

All pesticides come with concerns regarding contact with humans and pets. Go to for more information on effective and safe use, plus information on what pesticides are legally permitted.


If the main nest cannot be located, control, not complete elimination, may be your only option. Once you eliminate the nest(s) in your home, use a residual spray along the perimeter of the foundation, edges of siding, windows and door frames. Spraying the ground around your home disrupts scent trails. In crawl spaces, spray the inside of the foundation and sill plates. Reapplication is necessary so check the label to see how often. As a preventive, boric acid is available in gel and injectable paste. It prevents and destroys existing rot without the need to replace the wood and acts as an insecticide.

Carpenter ants are not all bad however. They recycle rotting wood into sawdust, which becomes compost for existing and new plants. They may even provide a valuable service to homeowners who – until they discovered the carpenter ants – never knew they had a rotting wood problem.

– Barb Galbraith and her family no longer share space

with carpenter ants in their farmhouse near

Oakville, Manitoba

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