Ants are one of the most successful groups of insects. They are social insects that live in colonies, which are usually located in the ground, but may enter buildings for shelter and/or food. Ants feed on practically every kind of food, but those entering homes are looking for sweets and/or protein containing substances.

About 700 species of ants occur in the United States. Of these, only about two dozen species commonly infest homes.

Pest ants are usually divided into two groups based on their typical nesting preferences, either wall nesting or ground nesting ants. The biology and habits of each species are different, so a detailed knowledge of these for each species is necessary for effective control.

The five most common wall-nesting ants are the carpenter ant, crazy ant, odorous house ant, Pharaoh ant, and the thief ant. The most commonly encountered ground-nesting ants are the Argentine ant, pavement ant, little black ant, velvety tree ant, and the fire ants.

House Ants

A wide variety of species are found throughout North America. Most feed on organic matter and are especially attracted by sweet foods. Colonies hibernate in the soil or in garden trash.

Carpenter Ant

The black carpenter ant, Camponotus pennsylvanicus (DeGreer) is a native
species and the common species in the east. These ants get their common name from their habit of hollowing out galleries in pieces of wood for nesting purposes. The nesting habit can result in structural damage. The tunnels they excavate in wood are clean, almost sandpapered in appearance, unlike termite tunnels. Carpenter ants are found throughout the United States.

The workers are about ¼ to ½ inch long and completely black except the top of the abdomen with long, pale yellowish hairs pressed against its surface. Other species will have various combinations of red and black, or completely red or brown. Although carpenter ants do not sting, their bites can be quite painful, especially when they inject formic acid into the wound.

The only external indication of infestation other than the presence of workers and/or swarmers is the appearance of small openings or windows on the surface of the wood. Through these, the workers expel debris, which consists of sawdust like shavings and/or fragments of insulation and insect body parts.

The first step in control is to determine if the ants present are merely foraging inside or if there is a nest inside. The best indication of a nest is the presence of sawdust piles containing insect body parts. Another indication is the sound produced as the workers remove wood to expand the nest. Outside check around the building's perimeter for foraging trails, especially in the direction of trees and shrubs; easiest to locate between sunset and sunrise when the ants are most active.

The second step is to locate any inside nests. Look for sawdust piles with insect body parts. Listen for ant sounds mentioned above; listening devices are helpful. Gently tap and listen for sound changes; nest cavities give a hollow or dull ring. Carpenter ants have a network of trails they follow throughout a structure and often use the tops of electrical wires and water
pipes. A moisture meter can be helpful in locating areas of higher moisture in which the ants prefer to locate their initial nests.

The third step is to determine if the inside colony is a parent or satellite colony. Detection of a trail directs one to the parent colony. For effective control, it is imperative to locate and eliminate the parent colony.

Once the colony or colonies are located, they should be treated directly with an appropriately labeled pesticide. Inside this may involve drilling wall voids and applying dust and/or drilling wood members and pressure injection. Barrier treatment is effective in preventing entry, with wettable or microencapsulated formulations working best. All branches of trees and shrubs in contact with the building must be trimmed back. Be sure to check where electrical and water lines enter the building and caulk any gaps.

Little Black Ant

This monomorphic ant gets its name from its very small size and jet black coloration. It is a native species and is found throughout the United States, especially in the eastern half.

Inside the nests are located in woodwork, decaying wood, and masonry. They feed on grease, oil, meats, fruits, vegetable materials such as corn mean, and sweets. While outside, they nest under stones/rocks, in rotting logs, in lawns, or in open areas. The workers feed on other insects, honeydew and plant secretions. They forage in trails, which can commonly be seen on foundation walls and along sidewalks outside.

Location of nest(s) and it treatment with a residual is ideal for control. Try following the ants back from the food source. Dusting the voids of outside ground floor walls and infested interior walls along with barrier treatment is effective.

Odorous House Ant

The pungent, "rotten coconut like" odor given off when this monomorphic brown to black ant is crushed gives it its name. It is a native species and is found throughout the United States.

Colonies may be composed of several hundred to 100,000 ants. There are usually many queens in a colony. These ants do swarm from May to mid July. The workers and queens live for several years. Individuals from different colonies are not hostile to one another and workers normally move along trails.

Inside, these ants usually construct their nests in wall voids especially around hot water pipes and heaters, in crevices around sinks, cupboards, etc. These ants prefer sweets but also eat foods with high protein content and grease such as meats and cheese.

Outside, they are often found in the nest of larger ants, in exposed soil, but mostly under objects. Workers feed on insects, seek honeydew and plant secretions, and even feed on seeds. They are extremely fond of honeydew and attend such honeydew excreting insects as plantlice (aphids), scale insects, mealybugs, etc. They are most likely to enter buildings when their honeydew supply is reduced such as during rainy weather or with leaf fall in the autumn.
For control, location of the nest(s) is crucial and can often be accomplished by following the trail of foraging workers back from the food source. Use of boric acid dust in voids of outside ground floor walls and infested interior walls along with barrier treatment is effective.

Pavement Ant

This monomorphic light brown to black ant gets its name from commonly locating its nest in or under cracks in pavement. Pavement ants were introduced from Europe by the early colonists. They are found in most of the eastern half of the United States.

Colonies are moderately large to large, averaging 3 to 4,000 ants and several queens. Winged reproductives appear outside primarily in June and July, but may emerge anytime inside including during the winter months. Workers have been shown to be an intermediate host of the poultry tapeworms.

Inside, pavement ants will occasionally nest in walls, in insulation, and under floors. The most likely place is in ground level masonry walls of the foundation and especially near some heat source in the winter. They often follow pipes, which come through slabs for access to upper floors of buildings.

Outside, these ants typically nest under stones, in cracks in pavement, and next to buildings. They enter buildings through cracks in the slab and walls, slab expansion joints, and the natural openings of buildings. Although not aggressive, workers can bite and sting.

These ants feed on almost anything including insects, honeydew, seeds, plant sap and household foods such as meats, nuts, cheese, honey and bread, but show a preference for meats and grease. They forage in trails, and for distances of up to 30 feet.

Location of the nest(s) and its treatment with a residual is ideal for control; try following ants back from the food source. Dust in the voids of outside ground floor walls, treatment of cracks in the slab with a residual, and barrier treatment is effective for control. The direct injection with an appropriately labeled high-pressure aerosol into the entrance/exit opening in the crack or expansion of a concrete floor is extremely effective.

Pharaoh Ant

The name Pharaoh ant, Monomorium pharaonis (Linnaeus), resulted from the mistaken belief that this ant was one of the plagues of Egypt in the time of the Pharaohs. Pharaoh ants are thought to be native to the African region. This ant is found throughout the United States. Pharaoh ants have been strongly implicated in the spread of various disease pathogens.

The workers are monomorphic, usually pale, varying from yellowish to reddish, with the abdomen often darker. Their colonies tend to be large with workers numbering in the thousands to several hundred thousand. There are usually several hundred reproductive females present in such a colony. Although winged reproductive females are produced, there are no flights of swarmers and mating takes place within the nest. New nests can be formed by "budding" with as few as 5 workers, 10 pre-adults, and one queen migrating from the original colony.

These ants are of particular importance in hospitals where they will enter wounds, enter in use IV bottles, seek moisture from the mouths of sleeping infants, etc. More than a dozen pathogenic bacteria have been found in Pharaoh ants collected in hospitals.

Inside, Pharaoh ants nest in warm, humid areas near sources of food and/or water. Nests are usually located in inaccessible areas such as wall voids, behind baseboards, in furniture, under floors, and between linens. The workers range widely from the nest in search of food and water, and establish trails to those resources. They commonly use electrical wires as a highway system to travel through walls and between floors.

Outside, these ants seem to be of little importance. In the temperate areas of the United States, they usually cannot survive outdoors year around.

They have a wide preference in food, ranging from syrups to fruits, pies, meats and dead insects. They use carbohydrates primarily for maintenance whereas, protein is primarily required for larval development and egg production by the queens.

Be cautioned that the typical use of liquid or dust pesticides actually makes the situation worse by causing the colony to fracture into several colonies.

Baiting is usually the only method of effective control. Use one bait station per line of ants. Locate it as close to the line of ants as possible without disturbing them.