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United States Department of Agriculture

Agricultural Research Service

Title: Host-Specific Attraction of Pseudacteon Flies (Diptera: Phoridae) to Fire Ant Colonies in Brazil

Author
item Porter, Sanford

Submitted to: Florida Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 1, 1998
Publication Date: N/A

Interpretive Summary: Host specificity is an important issue that needs to be resolved before the introduction of exotic biocontrol agents to control imported fire ants; consequently, a USDA scientist from the ARS Center for Medical, Agricultural and Veterinary Entomology in Gainesville, Florida, tested the host specificity of parasitic phorid flies at field sites in southeastern Brazil with fire ants in the saevissima and geminata complexes. The host suitability of these two fire ant complexes is an important biocontrol question because all native fire ants in the United States are in the geminata complex while both of the imported fire ants in the United States are in the saevissima comlex. These flies showed a strong preference for fire ants in the saevissima complex. No Pseudacteon flies were attracted to Solenopsis geminata colonies when they were set out in trays by themselves. Even when both species of ants were placed together side by side, more than 99% of flies were found over trays with saevissima complex ants. Altogether, 262 flies emerged from the saevissima complex colonies, while no adult flies emerged from the S. geminata colonies. These results demonstrated that at least two most common species are hightly specific to saevissima complex fire ants and will pose little threat to native fire ants when they are released as biocontrol agents for imported fire ants in the United States.

Technical Abstract: 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 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 were 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 ceased activity. 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 (50% Pseudacteon tricuspis, 39% Pseudacteon litoralis, 2.7% Pseudacteon pradei, 1.5% Pseudacteon wasmanni, 0.3% Pseudacteon curvatus). 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.

Last Modified: 9/10/2014
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