| Endoparasitoid phorid flies, Pseudacteon spp. (Dipte: Phoridae) are important biological control agents of imported fire ants Solenopsis invicta , and S. richteri (Hymenoptera: Formicidae). The impact on phorid particularly insect growth regulators, used in controlling imported fire ants has yet to be explored. Red imported fire ants parasitized by Pseudacteon tricuspis were exposed to methoprene and pyriproxyfen, the active ingredients used in some fire ant baits. These chemicals are insect growth regulators (IGRs), which affect the reproductive capabilities of the colony, but have no acute toxicity to fire ant workers. An experiment tested the effects of the two IGRs on the phorid fly larva at two time intervals (days 6 and 10 post-parasitism) when the larva was present in the thorax and head of the adult ant host, respectively. The mean proportion of emerged P. tricuspis from methoprene and pyriproxyfen treatments was significantly reduced relative to the control. Timing of exposure to the IGRs (days post-parasitism) did not have a significant impact on the emergence of the phorid fly. From 1995 to 2009, four Pseudacteon spp. were released in the U.S. with three species, P. curvatus, P. tricuspis, and P. obtusus released in Arkansas. To determine Pseudacteon establishment and expansion, sticky traps were used to monitor phorid fly species at and near 10 release sites, in counties bordering neighboring states, and along regional transects. Pseudacteon flies were captured in 16 Arkansas counties: Ashley, Chicot, Clark, Desha, Drew, Hempstead, Howard, Little River, Montgomery, Nevada, Perry, Phillips, Pike, Polk, Sevier, and Union. P. curvatus was found in areas far from release sites, suggesting dispersal from neighboring states. The range of P. tricuspis evidently also expanded from its initial release sites in southern Arkansas. |
