Pharaoh ant distribution and population monitoring

Public Health Significance of Urban Pests 181

6.3. Exposure and risk assessment, with risk based on geographical location

6.3.1. Pharaoh ant distribution and population monitoring

Colony proliferation by budding, with and without the presence of mature queens and the suitability of small harbourages as nest sites, has contributed greatly to the worldwide spread of Pharaoh ants via commerce. This spread probably occurred before and after the original description by Linnaeus in 1758 of a Pharaoh ant specimen collected in Egypt. Pharaoh ant infestations are documented throughout Europe and North America Edwards, 1986. In tropical and subtropical climates, infestations can extend outdoors; in temperate areas, heated buildings and man-made heat sinks permit winter survival and even colony growth Kohn Vlˇcek, 1986; Vail, 1996. Colonies can have intercon- nected nest sites, and movement to suitable habitats, as environments change, permits the ants to become established in new sites. The movement of infested articles, packa- ging and luggage can also initiate infestations in buildings Smith, 1965. Buildings with a high turnover or exchange of occupants, or shared services such as laundry and equip- ment, such as hospitals and hotels, may have a higher risk of infestation Edwards Baker, 1981. Monitoring populations of Pharaoh ants includes visual counts of trailing ants or counts of the number of trails present. Because Pharaoh ants are omnivorous, a variety of food lures such as raw liver, jelly, peanut butter, honey and sugar solutions have been used to locate and quantify their presence, generally for research studies Edwards Clarke, 1978; Haack, 1991; Oi et al., 1994. In laboratory testing, Williams 1990b reported lard and several types of honey as being most accepted by Pharaoh ants. In general, a food lure is placed at various intervals on the interior and exterior of a building and near a suspected harbourage, and near food and water sources. After 2–24 hours depending on foraging activity, lures are examined for Pharaoh ants, with the lure location and num- ber of ants recorded.

6.3.2. Fire ant geographic range and potential expansion