Home Inspections Metro Pittsburgh Area

Alltech Inspection Services - Wood Boring Pests

Carpenter Ants

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There are several species of carpenter ants that may be found infesting homes and other buildings. Normally workers are black or red and black in color and range in size from 3/8 to 1/2 inch. Winged queen ants may be as large as one inch. However, size is not a reliable characteristic to identify carpenter ants. Ants are divided into different castes, i.e. workers, queens, and males. Some ants, including carpenter ants, have polymorphic workers, which means that within one species the workers occur in different sizes. The best method to separate carpenter ants from other ants is by the following characteristics:

  • a waist with one node (petiole)
  • a thorax with an evenly rounded upper surface

There are other ants that appear similar and are occasionally mistaken for carpenter ants. They may have one or two nodes. However, they can be distinguished from carpenter ants by the uneven profile of their thorax. These ants are usually not wood-infesting, so it is important to correctly identify the ants before control is attempted as control strategies vary with different ant species.

Ant or termite: Carpenter ants differ from termites by having dark-colored bodies, narrow waists, elbowed antennae, and if present, hind wings shorter than front wings. Carpenter ants are very common and are frequently seen in the open. Termites are light-colored, have no waist constriction, have straight antennae and, if present, wings are of equal length. Termites are much less common. They avoid light and are rarely seen outside of their colony.

What they eat: Carpenter ants feed on sources of protein and sugar. Outdoors, carpenter ants feed on living and dead insects. They are also very attracted to honeydew, a sweet liquid produced by aphids and scale insects. Aphids and scales feed on trees, shrubs, and other plants. Indoors, carpenter ants feed on meats, as well as syrup, honey, sugar, jelly, and other sweets. Carpenter ants DO NOT eat wood. They remove wood as they create galleries and tunnels. Most foraging is done at night between sunset and midnight during spring and summer months. Sometimes workers travel up to 100 yards from a nest in search of food.

Where they live: Carpenter ants nest in moist wood including rotting trees, tree roots, tree stumps, and logs or boards lying on or buried in the ground. They can also nest in moist or decayed wood inside buildings. Wood decay may be caused by exposure to leaks, condensation, or poor air circulation. Nests have been found behind bathroom tiles; around tubs, sinks, showers, and dishwashers; under roofing, in attic beams, and under subfloor insulation; and in hollow spaces such as doors, curtain rods, and wall voids. Carpenter ants may also nest in foam insulation.

A parent carpenter ant colony sometimes establishes one or more satellite nests in nearby indoor or outdoor sites. Satellite nests are composed of workers, pupae, and mature larvae. A satellite nest does not require moisture because the workers do not tend eggs. For this reason, satellite nests can be found in relatively dry locations, such as insulation, hollow doors, and sound wood. The workers of satellite colonies move between their nest and the parent colony. In late summer, winged queens and males may emerge from pupae transported into satellite colonies. They may appear in structures in late winter and early spring as they swarm from a satellite nest.

During spring it is common to find carpenter ants in homes. It is important to try to determine whether the ants are coming from an outdoor or an indoor nest, although this can be difficult. Their presence is not sufficient evidence to conclude that there is a nest in your home. You may be able to make a more accurate determination based on when you first see carpenter ants. If you find carpenter ants in your home during late winter or early spring, that suggests the ants are coming from a nest in the building. However, if you see activity later in the year, it is less clear if the nest is in the building.

You may also see carpenter ant swarms during spring. Carpenter ants produce large numbers of queens and males during late summer. They emerge from nests the following spring for their nuptial flights. After mating, queens search for suitable sites to begin new nests. Once they land, their wings break off and each queen attempts to construct a new nest.

When carpenter ant nests are indoors, mating swarms become trapped inside. Finding large numbers of winged ants indoors is a sure sign that an indoor nest exists and may give the approximate location of the colony. Finding one to several winged queens does not automatically mean a nest is present indoors. It is more likely the queens have just mated and have entered the home, searching for nesting sites. Wingless queens found walking indoors are new queens that have recently shed their wings but are still searching for nesting sites. They are not an indication of an indoor nest.

In almost all cases, carpenter ants seen indoors during winter are an indication that there is an inside nest. One exception is when ants are brought indoors in firewood. Workers from firewood are not able to start nests in homes, nor do they damage wood structures in buildings. Workers may become active during winter if the nest receives sufficient warmth from sunlight, mild outdoor temperatures, or from indoor heat. It is not clear whether just a few workers break dormancy or the entire nest becomes active. When ants are active during winter they will forage at night, searching for moisture. It is common for a home dweller to enter a room early in the morning, turn on the lights, and see ants scurrying for cover. Common places to sight them are cabinets, sinks, dishwashers, rolled-up towels, bathroom tubs, sink and toilet areas, or other places where moisture is abundant. On a bright sunny day, ants may be seen walking randomly through different areas of the house.

It is also possible for a carpenter ant nest to exist in a house during winter but not be noticed. If the nest exists at a site that does not receive sufficient indoor heat or sunshine, e.g. a north-facing outside wall, the ants will remain dormant until spring.

An important method for preventing carpenter ant problems indoors is to eliminate high moisture conditions that are attractive to them. Also, replace any moisture-damaged wood. Be careful that wood or lumber that is stored in a garage or near the house is kept dry and, if possible, elevated to allow air circulation. Store firewood as far away from buildings as possible. Remove tree and shrub stumps and roots. Trim branches that overhang the home.

Finding the Nests: In order to eliminate carpenter ants nesting indoors, you need to locate and destroy their nest. The nest may be located by careful and patient observations of worker ants, especially between sunset and midnight during spring and summer months when carpenter ants are most active. To follow carpenter ants without startling them, use a flashlight with a red film over the lensóants cannot see red light. You can increase your chances of following workers to their nest by setting out food that is attractive to carpenter ants. Place food in areas where you find workers. Many foods are attractive to carpenter ants, including honey or other sweet foods.

During spring carpenter ants are particularly attracted to protein sources, such as tuna packed in water.(not oil.) Set out small pieces of tuna for the ants to take back to their nest. It is easier to follow the ants when they are carrying food. With patience and perseverance, you can follow the ants back to their nest.

Control: The best method to control carpenter ants is to locate and destroy the nest, replace damaged or decayed wood, and, if they exist, eliminate moisture problems. Eliminating a carpenter ant nest is a difficult and challenging task. It is possible for a home dweller to control carpenter ants on their own. However, in most cases, control should be performed by an experienced pest control applicator. They have the experience and a wider array of products to more effectively control a carpenter ant problem. Home dwellers can still play a crucial role in control programs by providing information to a pest control provider, such as when, where, and how many ants were seen.

Indoors: Nests are often concealed in wall voids, ceilings, subfloors, attics, or hollow doors. It is usually necessary for a professional pest control applicator to drill small (about 1/8 inch) holes and apply an insecticidal dust into the nest area. It is best to determine the nestís location as specifically as possible. Control should not be applied randomly through the home. There are no insecticides available to the public that are labeled for this type of application.

How much damage: The damage to wood structures is variable. The longer a colony is present in a structure, the greater the damage that can be done. If structural wood is weakened, carpenter ant damage can be severe.

Baits: If the nest cannot be located, baits may be an effective alternative. Baits work by combining an attractive food source with a slow-acting toxicant. A delayed toxicant is critical because it allows the ants to forage normally for days or even weeks. During that time, ants consume the bait and return to the nest to share the bait with the rest of the colony. In a process known as trophallaxis, one ant regurgitates its stomach contents to another ant. This food sharing behavior enables the bait to be spread throughout the colony before the toxicant takes effect.

There are a few baits available to nonprofessionals for carpenter ant control. Most retail products are liquid or granular formulations containing hydramethylnon, sulfluramid, abamectin, or boric acid. Baits vary a great deal in their effectiveness. Carpenter ants have complex food preferences, and some of the sugar-based baits will not be attractive to the ants long enough to be successful.

The keys to successful baiting are placement and monitoring; a bait cannot be effective if it is never encountered by ants. Place the bait only in areas where activity has been seen or is strongly suspected. After offering the bait, monitor it over 24 hours for feeding activity. Any bait that is ignored should be substituted with another, and any that is consumed should be replenished. Remember that increased ant activity around baits is a good sign. Never apply insecticides on or around baits because this will prevent feeding and render baits useless. Do not spray or dust other areas of the home, especially where carpenter ants are seen, as this can reduce the effectiveness of the bait. Be patientóbaits can take weeks or months to achieve control. Professional pest control personnel are trained in baiting techniques and have access to a wider variety of products than consumers. They are more likely to achieve positive results. Contact a licensed pest control company if you prefer the expertise and experience of a professional.