[March Pest Profile]

Pharaoh ant

Scientific Name: Monomorium pharaonis (Linnaeus)
Order/Family: Hymenoptera/Formicidae 

Description
Pharaoh ants are very small; workers are about 1/16-inch long. They range from yellow to light brown. The thorax lacks spines, and the petiole has two nodes. These ants can be distinguished from thief ants because they have a three-segmented club at the end of the antenna.

Biology
These ants do not swarm; females mate in the nest, and new colonies are formed by “budding.” This means part of the main colony moves en masse to a new location. There may be hundreds of thousands of ants in a colony. A female produces 350 to 400 eggs in her lifetime. The entire life cycle is completed in 38 to 45 days at room temperature. Indoors these ants develop year round. Workers live for approximately nine to 10 weeks, and queens live four to 12 months.

Habits
Pharaoh ants are widely distributed throughout the United States. They can nest outdoors, and they are major problems in homes and institutions such as hospitals, hotels or apartment complexes. They nest in warm, hard-to-reach locations in walls, subfloor areas, wall sockets, attics and behind baseboards. Pharaoh ants eat insects but prefer meats or greases. They also feed on sugar syrup, fruit juices, jellies and cakes. These ants are an especially important pest in hospitals where they have been found infesting the dressings on patients’ wounds, feeding on secretions from newborns, in IV tubes, etc.

Control
Because they nest in such a wide variety of locations, Pharaoh ants are very difficult to control. Since they do not necessarily follow specific trails to food sources, they are difficult to trace to their nests; however, it is useful to look near sources of water and food.

A successful Pharaoh ant control program involves intensive baiting using baits that contain insect growth regulators or slow-acting and non-repellent toxicants. Baits should be placed in areas where ants are active. Baits should be placed behind outlets, switch plates, areas where wires pass through walls and in cracks and crevices, along straight lines, such as the edge of baseboards. If the ants are avoiding the bait, another bait formulation should be used. Baits should be replaced as necessary. Several follow-up visits may be needed each month until control is achieved. Elimination of Pharaoh ants from a structure might require a year or more of vigilant baiting.
Residual applications of insecticides should not be used to control Pharaoh ants. These applications effect less than 5 percent of the workers in a colony, stress the colony and cause the colony to split, leading to colonization of new areas with very little reduction in the existing population. It is important that this is explained to customers who might feel compelled to take things into their own hands.