Ants are found everywhere and, like termites, bees, and wasps, are social insects that live in colonies consisting of thousands of individuals. Because they are so numerous, pest management companies rate ants as the number one insect problem they encounter in residences.
Carpenter ants are the most important structural insect pest in many areas of the Pacific Northwest (PNW) because of their habit of constructing nests inside dwellings. They are particularly common in the spring. Homes near forested lands tend to have more carpenter ant activity than do those in suburban or urban areas. Large black ants - often carpenter ants - may frequently be found throughout a house, both inside and out, as well as in surrounding areas. Color is not a reliable identifying characteristic: in the PNW there are several species of carpenter ants that vary from black, to red and black. Carpenter ants vary in size within each species. The most common carpenter ant infesting structures is Camponotus modoc, a black ant with red-brown legs.
Carpenter ants commonly nest in standing trees (living or dead), stumps, logs, or on the forest floor. Worker ants from a large "parent" colony, found outside, will frequently move into a dwelling as a "satellite" colony. Workers, often in the thousands, appear in different size classes: majors, medias, and minors. Major workers are called soldiers of the nest, while minor workers mostly expand the nest and collect food. Communication and travel between the colonies are maintained, and the satellite colony may contain larvae, pupae, and winged reproductives. Only parent colonies contain the functional queen, eggs, and early instar larvae.
Each spring, carpenter ant nests release large numbers of winged females and males. Do not be too alarmed by this phenomenon; most of the inseminated queens die before they can start new nests. The queens mate with winged males and quickly shed their wings; thus, you rarely see ants with wings after the swarm.
Carpenter ants do not eat wood, they only nest in it. They eat protein (dead insects) and sweets, especially aphid honeydew, collected from outdoors. Because carpenter ants can build nests in sound, dry wood as well as in wall voids, crawl spaces, and within foam and other insulation, they are capable of causing structural damage and must be taken seriously.
There are several ways to detect a carpenter ant nest. You may find sawdust piles near ant entryways. The sawdust is kicked out as digging proceeds. You may observe ants trailing into or out of the dwelling, perhaps through a crack or under the siding (this, by itself, does not locate the nest, it only indicates the presence of one or more nests somewhere inside). You also may hear scraping sounds made by worker ants as they enlarge the nest inside a wall or rustlings of the winged reproductives (the house must be very quiet). Finally, nests often are uncovered during remodeling/construction.
In early spring, before aphids and other food is abundant, workers may forage indoors for water, often in kitchens and bathrooms. Common but overlooked passageways into a house are routing holes for telephone, TV, and electrical cables, especially if the cables pass near trees that harbor aphids.
Control of carpenter ants is best left to competent pest management professionals. They have the experience and the tools necessary to locate nests and apply pesticide products effectively and safely. Drilling wall voids, applying materials inside, underneath and in attic spaces may not be necessary to control carpenter ants, as exterior perimeter treatment with non-repellent materials will control them. If performed during the high foraging season, pesticide is transferred among ants, ultimately eliminating the nest in the structure. When carpenter ants are seen inside during winter, it is best to vacuum them up and wait until the spring foraging season to initiate treatments. Certain bait formulations containing indoxacarb or thiamethoxam have been used successfully against carpenter ants. However, carpenter ants can be finicky eaters, so baits are not always effective. Carpenter ant insecticides for use in wall voids or as a perimeter treatment include bifenthrin, boric acid, cyfluthrin, cypermethrin, deltamethrin, fipronil, and permethrin.
Moisture ant queens are often mistaken for queen carpenter ants but are lighter in color and smaller. Moisture ant workers are yellow to dark brown and all the same size. Moisture ants are frequently associated with rotting wood in houses. The colony usually starts in decayed wood (often in cellulose debris within crawl spaces) and workers then bring moisture into the structure, thereby increasing damage. When you find these ants, it should alert you to search for a wood decay problem in or under the building. Removing infested wood and controlling moisture eliminates most moisture ant problems.
These ants are an indication of wood decay problems in or under the building. Removing infested wood and controlling moisture eliminates most moisture ant problems.
Velvety tree ant
Velvety tree ants get their name from a glistening abdomen comprised of dense, fine hairs. Two species may infest structures: the red and black California velvety tree ant (red thorax, black head and abdomen) and a second, entirely dark brown species. The size ranges from 0.13 to 0.25 inch (3-6 mm) long, depending on which of the two species is encountered. Workers, when crushed, give off a distinct odor similar to that of an odorous house ant.
Velvety tree ant infestations resemble those of carpenter ants. They are capable of mining wood, only to a lesser extent. They also infest foam insulation. The nests are usually located outside a structure. A colony of these ants may have many queens and numerous nest sites. Velvety tree ants form trails into buildings for nesting purposes, but typically are not seen around human or pet food. They primarily feed on honeydew and insects.
Living and decayed portions of trees and branches should be removed from around the house. Treatments similar to those used for carpenter ants have been effective for velvety tree ant infestations.