It is important to note that of the ants found indoors, only a few species are responsible for the majority of infestations. Identification of the ant helps the technician identify possible sites of the infestation. However, baits can be placed in infested areas while the technician is having the ants identified.

If ants are found in a building, an important first step is to determine whether the ants from a colony located inside or outside the structure.

Indications that a colony is inside are when:

  • ant workers are consistently found inside over a long uninterrupted period
  • nest building is observed inside (Look for wood shavings of carpenter ants, "dumping" of materials by ants, etc.)
  • the colony is located in the upper floor of a building, or
  • inside swarming is observed.

Indications that a colony is outside are when:

  • ants inside can be "trailed" outside
  • ants outside can be seen coming inside
  • nesting sites outside are near the structure with an inside infestation - look for mounds next to the foundation, or trees with large carpenter ant colonies touching an infested portion of the building or
  • ants nest under slabs or swarm inside, but workers do not forage inside.

Whether the colony is inside or outdoors, ants that are known to tend aphids for the sweet liquid ("honeydew") that they produce often seek food inside before this food is available outdoors. After populations of aphids and similar insects increase (in late spring), ants may disappear. They may return in dry weather seeking moisture, but often will not be seen until the next spring. When pest control efforts occur during this period, it is often difficult to tell whether the pest management methods are effective or whether the ants left the building because of other food sources.


Control and Management


  • Get all information possible by talking to the staff.
  • Observe ant worker movement and plot on a diagram if need be. Try to target "hot spots" of the infestation.
  • Use traps baited with a grease and a sugar or syrup or other ingredients like peanut butter and cookie crumbs.

Inside - Inspect holes and cracks where workers enter, old or new moisture stains, food accumulations (such as bird seed or food for classroom pets), activity near appliances (dishwasher and washing machines), near showers, in drawers, adjacent rooms or rooms above and below activity.

Outside - Inspect for workers behind vines, shrubs, other plants near the building, expansion joints, slabs, patio blocks, bricks, boards, plant pots, under and inside wooden columns and pillars, outside door and window frames, window wells, where telephone wires and air-conditioning refrigerant pipes enter building walls, trees that harbor colonies and provide access to buildings by overhanging limbs that touch, water meters and storm drain inspection manholes. Outside of ground-level rooms, inspect plants for aphids being tended by ants.

Habitat and Harborage Reduction

  • Caulk where pipes enter walls and seal masonry cracks. Check utility lines, air conditioning, refrigerant pipes, phone lines, etc.
  • Tighten door and window frames.
  • Repair water leaks.
  • Trim vegetation so it does not touch the building.
  • Remove items stacked close to buildings such as boards, stones, etc. that encourage ant nests; screen openings in hollow pillars, columns and ventilators

Pesticide Application

  • Whenever possible, baits should be used to control ant colonies. Use baits with slow-acting stomach poisons or with insect growth regulators. Baits are excellent in sensitive areas, such as computer rooms. When using baits always remember that students will not leave baits alone if they know where they are located. Do not spray or dust around baits - ants and other insects can detect tiny amounts of repellent chemicals. Never store baits or bait materials where they can be contaminated with any other odors, especially fumes of pesticides.
  • If the nest is located, use the "crack and crevice" treatment method; use dust in wall voids or canned pressurized liquid pesticides fitted with a tube for crack and crevice application. (Tubing can be obtained in long lengths and can be threaded through construction elements to treat areas distant from the pressurized can.)
  • Apply wettable powder or microencapsulated spray formulations where pesticides may be absorbed into porous surfaces.
  • Drill holes where practical into areas such as false floors in sink cabinets, window frames, wall panel grooves and other voids to deliver the pesticide where it is needed.
  • Outdoors, use bait stations designed for outdoor use or insecticide granules labeled for control of ants outside.

Reinspect the facility or contact staff with troublesome ant control problems within one week to 10 days depending on the control strategies. If using insect growth regulators (IGRs), remember that IGRs take longer than dusts to show results. Remember, pesticide treatments can repel ants and make them active in other areas. Colonies with multiple queens may break up into several colonies.


Black Carpenter Ant

The large, black workers range in size from ¼ inch to almost ½ inch. (Carpenter ants are usually entirely black, but some carpenter ants may be reddish-black.) Outside workers can be confused with field ants which do not enter structures. Workers will search for food 30 feet or more from the colony.

The colony may be found in wood (such as a fallen log, tree hole, stump or a structure wall). When carpenter ant workers dig nest tunnels, they chew out small pieces of wood. Unlike termites, they do not eat the wood; they drop it out of the nest area or pile it in one place. This pile of carpenter ant shavings, called sawdust, is very soft and is made up of pieces like a fine chisel would make. (Gritty construction sawdust in attics or on sills can be left over from construction or repairs and may be mistaken for carpenter ant shavings.) Carpenter ants do not put mud into their tunnels like termites; carpenter ant tunnels have very smooth sides. A nest or colony might harbor several thousand ants. Large colonies of carpenter ants can cause structural damage, but the colony more likely will be found partially in structural wood and partially in void spaces (such as between roof boards, between studs under windows or between subflooring and shower bases).

Black carpenter ant workers forage for sweet foods (such as honeydew from aphids and juices from ripe fruit) and insects. Indoors, they like sweets, meats, fruit juices and moist kitchen refuse


Control and Management

A thorough inspection is critical to successful control of carpenter ants. It is important to discover whether carpenter ants are nesting inside or outside. If ants are nesting inside:

  • their presence usually indicates a moisture problem in the building and
  • they have excavated tunnels (galleries) for harborage in structural wood.

Carpenter ants are often found near a roof leak or other damp wood. In many cases, Carpenter ants make their nests in wood that has been wet and infested by a brown rot fungus. Dark fungus stains on the wood is an indication of the presence of such moisture. Moisture in wood can be caused by :

  • improper attachment of wooden additions, dormers and hollow wooden columns that absorb moisture
  • porch floors, door sills, down spouts or areas where water collects or drains toward the building
  • regular gutter overflow pouring rainwater down the side of the building as well as back onto roof boards and soffits, etc.
  • leaking roof valleys
  • improper flashing, especially around chimneys, vents and skylights
  • improper roofing or holes in the roof
  • window sills directly exposed to rain, or
  • lack of ventilation in any area where moisture accumulates, such as around any leaking plumbing or drains (especially shower drains), unvented attics and crawl spaces, or unvented dishwashers, washing machines, ice machines, etc.

The many nesting sites, foraging entrances and food and moisture sources offer clues for inspection and location of the nest. The area where the majority of ant activity is seen may identify a nest site if entry from the outside can be ruled out. Carpenter ants are more active at night, so inspecting the area with the aid of a flashlight may be helpful.

Habitat and Harborage Reduction

  • Where nests are located inside, remove and replace infested structural wood.
  • Repair or seal areas where moisture dampens wood.
  • Wherever possible, caulk and screen area where ants can enter the building.
  • Ventilate indoor spaces where moisture accumulates, grade soil so water drains away from the building where necessary and repair roofing, guttering etc.
  • Trim trees where branches touch a structure or overhang roofs.

Pesticide Application
Eliminating colonies and nesting sites is a primary way to eliminate carpenter ant infestation.

  • Place baits in areas where foraging ants can discover them. Carpenter ants are more difficult to control with baits than other species. Place baits in areas inaccessible to students.
  • Remember to use enough bait stations to control the colony.
  • Use pesticidal dust or pressurized canned aerosols when nests are found in wall voids. Sprays are less effective.
  • Avoid using flushing agents because hundreds of ants may remain unaffected and can relocate the colony in a matter of hours or less to trunks, storage boxes, furniture drawers and other voids.
  • Aphids or other honeydew producing insects should be treated with pesticides, such as oils or soaps, that will not eliminate beneficial predators and parasites.
  • If a tree with rotted areas is present, one should contact a professional who can determine if it should be removed.

Carpenter ant infestations often cannot be controlled in one visit. Thorough inspection is needed to make management effective. Monthly inspections also assure that necessary repairs have been made.


Pavement Ant

The Pavement ant is brown or black and about 1/8 inch long. Pavement ants nest outside under rocks, at the edge of pavement, door stoops and patios. They commonly move their colonies inside between the foundation and sill plate. Outside, pavement ants tend honeydew-producing insects and feed on other insects and seeds.

Pavement ants store debris in certain areas of the colony or nest. When this area is needed to enlarge the nest, workers remove materials such as sand, seed coats, dead insect parts and sawdust from the building construction and dump them outside the colony. Colonies located on foundation walls drop debris over the side in a pile on the basement floor.


Control and Management


  • Inspect along the sill plate in the basement and around heat ducts and baseboards in areas where ant workers are active.
  • Look for foraging in the kitchen; such activity may indicate a nest in the basement below or just outside.
  • Outside, look for tiny mounds next to the building near windows and doors or nest openings under stones.

Habitat and Harborage Reduction

  • If ants are a chronic problem in the building, remove stones that shelter ant colonies.
  • Improve indoor sanitation, including the elimination of moist garbage in dry weather.
  • Caulk observed ant entrance points.

Pesticide Application

  • Place baits in areas where foraging ants can discover them. Always place baits in areas that are inaccessible to students.
  • If baits do not eliminate the colony, apply dusts or sprays in cracks and crevices of baseboard molding where activity is noticed. Continue to search for the nest.
  • Treat cracks around kitchen sinks and cabinets.
  • Treat cracks along foundation walls, under sill plates and cracks near heat ducts.
  • Be careful not to contaminate heat or air-conditioning ducts.
  • Treat cracks in slab foundations as well as the base of outside door jambs.


  • If baits applied inside fail to control the colony, treat nests.
  • Treat cracks and entry points.

Follow-up is usually not needed, but where control is unsuccessful, an intense inspection is required.


Odorous House Ant

The odorous house ant is brownish-gray in color and around 1/8 inch long. The body of the odorous house ant is relatively soft and can be easily crushed. When this occurs, a foul odor is released. Outdoor nests are shallow and are located under stones and boards. Inside, a colony can nest in many types of cavities. The workers trail each other. Outside they actively tend honeydew-producing insects and take flower nectar. Inside, workers seem to prefer sweets.


Control and Management


  • Begin by investigating locations where ant activity is observed.
  • Always inspect outside close to the location of inside activity. Look under stones and boards for colony openings and activity.
  • Do not use sprays with pyrethrins (which irritate but may not kill), causing the colony to split itself and relocate, as with the pharaoh ant.

Habitat and Harborage Reduction

  • Remove stones and boards harboring odorous house ant colonies.

Pesticide Application

  • Bait stations with a long active period are effective, but should not be contaminated by sprays or dusts that may be repellent. Place an adequate number in or near harborage. Always place baits in areas inaccessible to students.
  • If baits do not eliminate the colony, use dusts or residual sprays applied in cracks and crevices in the area of entering worker trails. Ant colonies should be sought outside as well as inside, unless its location inside prevents its reaching the outside.
  • Control populations of honeydew-producing insects on plants near the building. Use pesticides registered for insects on plants. To maintain predator and parasites of these plant insects, use low-toxicity pesticides such as insecticide soaps and oils.

Impress the staff with the need to control honeydew insects on plants and to eliminate nest harborage near structures.


Pharaoh Ant

The pharaoh ant is a tiny ant, dull-yellowish to light-orange in color and not much more than 1/16 inch long. Ants prefer warmer buildings and warm areas (80-85° F.) in buildings for nesting. These ants are active year-round in large buildings. Nesting sites include wall voids, cracks in woodwork, stacks of paper, envelopes, harborage in desk drawers, etc. It is common to find many colonies in one building and, perhaps, several in one room. Colonies have multiple queens and increase by dividing: one portion of the colony going with each queen. No swarms have been recorded, so new infestations are apparently transferred by moving infested objects.

Pharaoh ants trail each other and are attracted to grease, meats, insects and sweets. These harborage and food preferences bring it to coffee areas, kitchens, paper and other supply storage, office equipment, medical storage, laboratory benches and many kinds of biological cultures.


Control and Management


  • Inspect where sanitation needs improvement.
  • Ants are found where food is available, particularly sugars: where coffee is made, lunches eaten and in desks where snacks are stored.
  • Inspect storage room spills, laboratory media, unwashed cups, areas near vending machines and kitchens.
  • Pharaoh ants are easily baited. Use small, nontoxic disposable peanut butter baited cups to demonstrate where ants are seen (such as desk drawers and opened food boxes).
  • Look at sources of water. These ants are attracted to dripping faucets; they drown in plant water bottles and coffee water held overnight. Floating ants are frequently the first sign that these ants are present.

Habitat and Harborage Reduction

  • Reduce stored supplies.
  • Clean, rearrange and rotate supplies to expose nests.
  • Clean food areas before the end of the work day and empty water containers that stand overnight.

Pesticide Application

  • Spraying can cause pharaoh ant colonies to break up into several smaller colonies and spread the infestation; baits are the most effective way to control these ants. Several baits are available for pharaoh ant control. Place a bait station where every positive monitoring trap was located. Always place baits in areas that are inaccessible to students.
  • Set commercial bait stations. One that uses a stomach poison well accepted by ants and a grain-based bait that includes ground insects are specifically manufactured for pharaoh ant control.
  • Use a commercial bait of mint apple jelly and boric acid. Inject small dabs of the material into cracks and crevices where ants are observed.

Reinspect by monitoring bait cups. When sprays or dusts are used, or when colonies are disturbed by inspection or habitat alteration, colonies may move or split.


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