Red imported fire ant (Solenopsis invicta) forager sizes and granular ant bait grit size selection in the presence of Pseudacteon spp. phorid flies

Pseudacteon spp. phorid flies continue to be released throughout the southern United States in an attempt to control the red imported fire ant (Solenopsis invicta). A recent study determined S. invicta foragers are smaller in size in areas infested with phorid flies as compared to foragers from non-phorid infested areas. Prior to this work, experimental manipulation of S. invicta colony worker sizes has been shown to affect colony performance and additional studies have demonstrated a differential in selection of bait particle sizes based on forager size. The objectives of this study were to determine the effects of phorid presence on S. invicta caste sizes at our field sites, and also to determine if a phorid fly mediated colony shift results in a change of bait size preference by S. invicta. This was accomplished by measuring bait recruitment to, and consumption of, four sizes of bait particles in areas infested with phorids and areas that were not infested, as well as measuring individual foraging ants head widths.