Research Reports: Indoor and Outdoor Foraging Locations of Pharaoh Ants (Hymenoptera: Formicidae) and Control Strategies Using Bait Stations

  • David H. Oi
  • Karen M. Vail
  • David F. Williams
  • Donald N. Bieman


While Pharaoh ants, Monomorium pharaonis (L.), are generally considered indoor pests, we observed these ants foraging at 51.7% of outdoor monitoring sites located on exterior wall surfaces of apartment buildings in contrast to 11.6% of indoor sites. The number of ants per infested monitoring site did not vary significantly with counts averaging from 46 to 118. Commercial bait stations containing a delayed action toxicant placed solely on the exterior walls of buildings, or outdoors, provided a 94% reduction in Pharaoh ant numbers within 1 week in contrast to a 9% reduction in untreated buildings. This was similar to the reductions from buildings treated with bait stations placed both indoors and outdoors. While a total of 3 ants were found indoors in treated apartments, indoor counts from untreated buildings also were low. Initial outdoor ant counts were 2 to 20 times higher than indoor counts, and the significant population reductions were attributed to a reduction in counts from outdoor sites.
Literature Review Articles