Host-specific attraction of Pseudacteon flies (Diptera: Phoridae) to fire ant colonies in Brazil

Pseudacteon fly host-specificity tests were conducted in the field in southeastern Brazil with Solenopsis fire ants in the saevissima and geminata complexes. These parasitic flies showed a strong preference for fire ants in the saevissima complex. No Pseudacteon flies were attracted to three Solenopsis geminata (F.) colonies when they were set out in trays, but many flies were quickly attracted to three trays with saevissima complex colonies when they were set out between the S. geminata colonies. Even when both species of ants were placed together side by side, more than 99% of flies hovered over trays with saevissima. complex ants. When all of the saevissima colonies were removed, leaving only the S. geminata colonies available, about 95% of flies flew away. Several flies, however, did transfer to the S. geminata colonies for a few minutes and at least one fly (P. wasmanni) attacked a few S. geminata workers. Altogether 588 parasitized workers were collected from the saevissima complex colonies compared to 12 from the S. geminata colonies. Two hundred-sixty-two flies emerged from the saevissima complex colonies (52% Pseudacteon tricuspis Borgmeier; 39% Pseudacteon litoralis Borgmeier, 4.6% Pseudacteon wasmanni Schmitz, 2.7% Pseudacteon pradei Borgmeier; 0.4% Pseudacteon curvatus Borgmeier). No adult flies emerged from the S. geminata colonies. These results demonstrate that P. tricuspis and P. litoralis are highly specific to saevissima complex fire ants and strongly indicate that they would pose little threat to native fire ants should they be released as biocontrol agents for imported fire ants in the United States.