BIOLOGICAL CONTROL Distribution and Abundance of Natural Parasitoid (Hymenoptera: Pteromalidae) Populations of House Flies and Stable Flies (Diptera: Muscidae) at the University of Florida Dairy Research Unit

From September 2001 through September 2002, house fl y and stable fl y pupae were collected weekly from three fl y habitats at the University of Florida Research dairy in northcentral Florida and evaluated for parasitism. Varying parasitism percentages were observed throughout the study but they were not affected by temperature, precipitation or fl y abundance. Of the 6,222 house fl y pupae and 1,660 stable fl y pupae that produced either a host fl y or a parasitoid, 26.9% and 26.7% were parasitized, respectively. Ten parasitoid species were recovered, with the genus Spalangia accounting for 85.7% of the total; the most common parasitoids attacking house fl y and stable fl y pupae were Spalangia endius Walker (33.9% and 27.3%), S. cameroni Perkins (27.9% and 40.6%), and S. nigroaenea Curtis (21.0% and 24.8%), respectively. Other parasitoids included one specimen of S. erythromera Förster and four specimens of Phygadeuon fumator Gravenhörst (Ichneumonidae). The percentage parasitism of pupae collected from bunker silos was higher than that of pupae from calf pens and open pastures. Spalangia cameroni was consistently recovered through the entire year. Spalangia nigroaenea was predominant in July, August, and September. Spalangia endius was most active from October to May with a peak of relative abundance in January.