Pharaoh ants, (Monomorium pharaonis), are small yellow ants about 1/16" long. They are easily confused with thief ants. To distinguish the two, it is necessary to look at the antennae. Pharaoh ants have twelve segments with a three-segmented club on the end, while thief ants have ten segments with a two-segmented club.
Pharoah ants are native to tropical Africa but are now distributed throughout the world. They are usually associated with heated buildings since they cannot survive outside year round in the majority of the United States. These ants will nest in any dark void in a structure as well as in folded bags or newspapers. In the subtropical United States they will nest outside in leaf litter, piles of bricks, potted plants, or under roof shingles.
Pharaoh ant colonies can become quite large, often containing as many as 300,000 workers with several queens. New colonies are formed by budding, when some of the workers, brood, and a few queens move to a new location. In warm areas where they can survive outdoors they will move from building to building.
Pharaoh ant management is more dependant on locating areas of ant activity than eliminating the colony, since they are so large and can spread so easily. Place jelly baits on 1" squares of paper or tape and place in damp, dark areas. These ants move along electrical wires, so an inspection should include areas where wires enter walls or appliances, as well as behind switchplates and outlets.
Pharoah ants will also nest in and around appliances such as refrigerators or stoves that have food or water around them. A useful tool for the management of this ant is to make a map of the site and mark locations where ants and their colonies are found. This will help to identify new areas of activity over time.
Sanitation is essential for Pharaoh ant management, since elimination of food sources will make them more receptive to insecticide baits. Residual insecticides should not be used for Pharaoh ant management. They can repel ants, forcing more colonies to form through budding while killing only a small number of ants.
During the first two to four weeks of the program, place baits containing an insect growth regulator and a food attractant inside a soda straw throughout the area of infestation. These should be located along edges and in corners where ants are most likely to encounter them. Placing baits inside straws will keep them fresh and away from people and domestic animals.
Replace these with boric acid/food attractant baits. One food bait is three parts honey: two parts peanut butter: one part mint apple jelly : one part egg yolk baby food. Commercial baits are also available. Exterior treatments may be necessary in subtropical areas of the United States or during the warmer months in northern areas.
Remember that both insect growth regulators and boric acid are EPA- registered pesticides, so your regional National Park Service Integrated Pest Management coordinator should be consulted before using these materials.
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