Effects of over-the-counter aerosol products on sociotomy of Monomorium pharaonis (Hymenoptera: Formicidae)

The Pharaoh ant, Monomorium pharaonis (L.), is a widely distributed invasive tramp ant species. Due to their ability to frequently relocate nest sites when disturbed, Pharaoh ants are particularly challenging to manage. This study examined the colony movement patterns of different colony sizes of the Pharaoh ant in response to chemical disturbances caused by varying over-the-counter aerosol insecticide application rates. Three aerosol products, 3 application rates, and 4 colony sizes were tested. Essential oil-based insecticides exhibited a higher probability of inducing budding at all colony sizes when applied at a high rate. In contrast, pyrethroid-based insecticides increased the probability of inducing budding at a low application rate. The number of workers present outside the main nest in the essential oil-based insecticide-treated group decreased with increasing application rate, whereas the number of workers present outside the main nest increased in pyrethroid-based insecticide-treated groups. Furthermore, the density of workers outside the main nest appeared to play a role in influencing the final nest site after budding. The number of worker ant carcasses observed on pyrethroid-treated surfaces was significantly greater than on surfaces treated with the essential oil-based insecticide and controls. The effects of aerosol product type, colony size, and insecticide application rate on Pharaoh ant colony movement are discussed.