PREDATION ON THE HORN FLY (DIPTERA, MUSCIDAE) BY TWO EUROPEAN SPECIESOF PHILONTHUS (COLEOPTERA, STAPHYLINIDAE)

Two European species of Staphylinidae, Philonthus agilis (Gravenhorst) and P. concinnus (Gravenhorst), were evaluated in the laboratory as p redators on immature stages of the horn fly, Haematobia irritans (L.). Both species were more effective as predators on the egg stage, but t here also was substantial predation on the larval and pupal stages. Th ere were no significant differences between the two species in predati on on any prey life stage. Reductions in adult horn fly emergence caus ed by predation by these two exotic species were similar to reductions caused by two commonly occurring indigenous staphylinid species of si milar size. Increasing the predator-prey ratio greater than 1:25 had n o significant effect on numbers of prey consumed by either predated sp ecies.