Sampling and Dynamics ofPseudacteon tricuspis(Diptera: Phoridae) in Louisiana

Abstract

The population dynamics of a fire ant (Solenopsis invicta Buren) parasitoid (Pseudacteon tricuspis Borgmeier) was studied in Louisiana. The objectives of this study were to understand the daily and seasonal population dynamics of P. tricuspis in the context of environmental variables, determine whether P. tricuspis populations were synchronized over local and regional scales, determine the sex ratios and frequency distributions of P. tricuspis at disturbed S. invicta mounds, and determine the minimum sample size and sampling methodology that would provide an estimate of the true relative abundance of P. tricuspis at any location. Daily patterns of relative abundance of P. tricuspis followed a quadratic pattern, with peak fly activity during the afternoon. Seasonally, P. tricuspis relative abundance was variable but tended to positively fluctuate with soil moisture levels. Peak seasonal population abundance occurred during the late summer and fall, whereas population abundance was lowest during the late winter and early spring. Population dynamics of P. tricuspis were found to be synchronized at local and regional scales. Sampling protocols were derived for sampling P. tricuspis populations in Louisiana to account for local spatial heterogeneity in relative population abundance. To obtain an estimate of the true relative population abundance of P. tricuspis, at least 15 S. invicta mounds should be sampled, preferably allocated in groups to different areas at a location to account for spatial population heterogeneity. Phorid fly sampling should be conducted during the afternoons during the summer and fall, when fly abundance is highest.