The decapitating fly, Pseudacteon tricuspis, has been introduced to the United States for the biocontrol of the exotic red imported fire ant, Solenopsis invicta. In order to understand the population structure of P. tricuspis on a local spatial scale, and relate P. tricuspis abundances to host social form and infection with the fire ant pathogenThelohania solenopsae, a study of P. tricuspis spatio-temporal dynamics was conducted for five consecutive weeks at three locations in Louisiana during the fall of 2005. The spatial analysis software program SADIE (Spatial Analysis of Distance IndicEs) was utilized to analyze the spatial and temporal patterns of fly counts at disturbed S. invicta mounds. No significant spatial associations were found between P. tricuspis counts and host S. invicta colonies infected withT. solenopsae. However, significant clustering of counts occurred when P. tricuspis populations peaked, and were associated with polygyne host colonies. Overall, P. tricuspis counts largely reflected a random temporal distribution, as count patterns were not stable.