Host specificity of fire ant decapitating flies (Diptera: Phoridae) in laboratory oviposition tests

Host specificities of 3 species of Pseudacteon decapitating flies (P. litoralis Borgmeier, P. tricuspis Borgmeier, P. wasmanni Schmitz) were tested in quarantine facilities in Gainesville, FL. Female flies from Brazil were placed into test trays containing either red imported fire ants, Solenopsis invicta Buren: tropical fire ants, Solenopsis germinata Forel; or native ants from 6 other genera Crematogaster, Pheidole, Aphaenogaster, Neivamyrmex, Forelius, Camponotus). Tests lasted 60-90 min. The 3 species of flies tested were all at least 15 times more likely to attack their natural host S. invicta, than they were to attack the native fire ant, S. geminata. More than 200 larvae resulted from numerous attacks on S. invicta workers. No larvae resulted from the few possible attacks on S. germinata or the other species of ants that were tested. We induced several P. tricuspis to attack a few S. geminata workers by mixing these workers in with freeze-killed S. invicta workers. One adult fly emerged from these attacks, demonstrating that P. tricuspis can develop in S. geminata workers. This indicates that the field release of P. tricuspis poses some risk to native fire ants; however, the extremely low rates of attack on S. geminata in the laboratory and in the field indicate that this risk would be minimal. The argument is made that this small risk is acceptable because, among other things, native fire ants are under much more risk from expanding populations of imported fire ants than they would be from imported Pseudacteon flies.