Dispersal and competitive impacts of a third fire ant decapitating fly (Pseudacteon obtusus) established in North Central Florida

► Pseudacteon obtusus is established in Florida and dispersing outward at 8-12 km/yr. ► Pseudacteon curvatus and P. obtusus are excluding the previously abundant Pseudacteon tricuspis. ► P. obtusus competes well with the very abundant P. curvatus, unlike P. tricuspis. ► Despite strong competition, the three flies were positively associated with each other. ► Release of P. obtusus did not measurably increase net parasitoid numbers.