ABSTRACT
The horn fly, Haematobia irritans (L.) and face fly, Musca autumnalis DeGeer, are important pests of pastured cattle in the United States. Both species reproduce in cattle dung (cowpats) dropped on pastures. Beneficial insects associated with cowpats in the United States are numerous and several species have been shown to play an important role in the regulation of horn fly and face fly populations during certain times of the year. However, these beneficial species still do not adequately prevent horn fly and face fly populations from reaching unacceptable levels during the fly season. Twenty-nine species of natural enemies of dung-breeding flies have been released in the continental United States to aid in the control of horn flies and face flies. Only nine of the twenty-nine species released thus far have been reported to be established but more are expected to be found during the next few years. The impact of the established species of natural enemies on dungbreeding pests has yet to be adequately documented.
