Predation on the horn fly by two European species of Philonthus

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