Diurnal patterns of ovipositional activity in two Pseudacteon parasitoids (Diptera: Phoridae) in Alabama L.C. “Fudd” Graham and Vicky E. Bertagnolli Department of Entomology and Plant Pathology 301 Funchess Hall ▪ Auburn University, Auburn, Alabama The first release of P. tricuspis was in Macon County in 1999 and the first release of P. curvatus was in Talladega County in The flies have spread over 50 km and 24 km, respectively, from each site. Ants used in the study were collected from the vicinity of these original release sites just prior to field data collection. Ants from four mounds per site were returned to the lab and were separated from the soil so clean colonies could be used for the field data collection. Mounds were placed into individual 52 x 40 x 13 cm trays lined with Fluon®. Upon arrival at the field site, air and soil thermometers were placed near the collection site. The four trays of ants were placed in shady areas of the release sites approximately 8 m apart. The four trays containing ants were agitated by shaking the tray. This was done to induce pheromone release by the ants in order to attract phorid flies. Thirty minutes after agitation, phorid flies were aspirated out of their tray using a double chambered aspirator unit until no flies could be observed in the tray. The flies were transferred from the aspirator to a small plastic holding container via a hole in the lid. CO 2 was introduced into the holding container to induce fly knock down. Upon knock down, the lid was removed from the container and flies were counted. After fly count, the container was placed in the shade to allow for fly recovery. The tray was again shaken to agitate the ants and collection moved to the next box. The collection process is repeated every 30 minutes until flies cease coming to the trays. Air temperature, soil temperature and humidity were also recorded every 30 minutes. Materials & Methods Two species of phorid fly are currently established Alabama. Pseudacteon tricuspis is established at five sites on populations of the red imported fire ant, Solenopsis invicta, and Pseudacteon curvatus is established at four sites on populations of a hybrid fire ant (S. Invicta x Solenopsis richteri). In South America, several species of Pseudacteon are often found at the same site and exhibit at least three behaviors that help explain how resources are partitioned (Porter 1997). Species attack different size fire ant workers (Morrison et al. 1997), select different periods of diurnal activity (Pesquero et al. 1996) or attack fire ants engaged in different activities (Orr et al. 1997). Phorids that have been introduced into fire ant populations in Alabama have no competition from other phorid species. We documented the diurnal activity of the two species of phorid fly that have been introduced into Alabama and that, currently, have no competition from other phorid species that attack fire ants. Results Fig 1. Daily activity patterns of P. tricuspis on six collection dates in Macon County Alabama. Fig 2. Mean daily activity patterns of P. tricuspis in Macon County Alabama. Fig 3. Daily activity patterns of P. curvatus on six collection dates in Talladega County Alabama. Fig 4. Mean daily activity patterns of P. curvatus in Talladega County Alabama. Mean daily activity patterns for P. tricuspis were similar to those found by Pesquero et al. (1996) in Brazil, with mean peak activity occurring during mid-day. In Brazil, activity was greatly reduced 12 hours following sunrise. However, P. tricuspis were still active in Alabama at this time (ca. 6 p.m.), extending ovipositional activity into hours when Pseudacteon litoralis is usually active in Brazil (Pesquero et al. 1996). Peak activity for P. curvatus occurred later in the afternoon 10–11 hours following sunrise, but moderate activity was observed from four to twelve hours past sunrise. Dates on graphs in Figs. 1 & 3 where collection of phorids is zero sometime during the day are dates when rain showers occurred during the collection period and phorids could not be collected because trays had to be covered. Introduction References Morrison, S. W., S. D. Porter and L. E. Gilbert Sex ratio variation as a function of host size in Pseudacteon flies (Diptera: Phoridae), parasitoids of Solenopsis fire ants (Hymenoptera: Formicidae). Biol. J. Linn. Soc. 66: Orr, M. W., S. H. Seike and L. E. Gilbert Foraging ecology and patterns of diversification in dipteran parasitoids of fire ants in south Brazil. Ecol. Entomol. 22: Pesquero, M. A., S. Campiolo, H. G. Fowler and S. D. Porter Diurnal patterns of ovipositional activity in two Pseudacteon fly parasitoids (Diptera: Phoridae) of Solenopsis fire ants (Hymenoptera: Formicidae). Porter, S. D Biology and behavior of Pseudacteon decapitating flies (Diptera: Phoridae) that parasitize Solenopsis fire ants (Hymenoptera: Formicidae). Fla. Entomol. 81: