Predation by the macrochelid mite, Macrocheles peregrinus Krantz, on the immatures of two dung-breeding flies, the Australian buffalo fly, Haematobia irritans exigua De Meijere, and the African buffalo fly, Haematobia thirouxi potans (Bezzi), was examined experimentally in the laboratory. Two systems were employed: i) 250 ml chambers containing a 50 ml dung mass artificially infested with known numbers of fly eggs and ii) 10 L chambers containing 1 L dung pads on which female flies had deposited known numbers of eggs. Predation caused significant levels of mortality in both fly species in both experimental systems. The suitability of the two fly species as prey for the mite was compared in two series of experiments using the smaller chambers. In one, 2, 4, 8, or 16 mites were added to dung masses each infested with 20 eggs. In the other, 8 mites were added to dung masses infested with 20 eggs at intervals before, during and after egg hatch. Neither test revealed significant consistent differences in the predatory effectiveness of the mite on the two fly species. It was concluded that with regard to predation by M. peregrinus, H. thirouxi potans was a satisfactory model for H. irritans exigua. The mite attacked the egg of H. irritans exigua in all stages of development and attacked newly hatched larvae of both fly species. Most larvae were secure from attack 24 h after hatching from the egg. In most experiments, even those at high predator density, many immature flies escaped unharmed.

Predacious mites, particularly those in the family Macrochelidae, are considered to have potential for biological control of dung-breeding flies (Axtell 1981, Tyndale-Biscoe and Wallace 1981, Wallace et al. 1979). Many species of mite are phoretic on dung beetles (Krantz 1978). The relative paucity of the phoretic mite fauna associated with native and introduced dung beetles in Australia led to a decision to select and introduce one African species, Macrocheles peregrinus Krantz, to Australia, with a view to increasing the level of mortality among the immatures of the buffalo fly Haematobia irritans exigua De Meijere (Bornemissza 1976, Krantz 1981, Wallace and Holm 1983, Waterhouse 1974). The mite is now established, widespread, and is abundant in many regions of northern Australia (Wallace and Holm 1983). M. peregrinus was selected principally because of its wide geographic distribution in Africa, its relative abundance and the wide range of dung beetle species upon which it is phoretic, including most of the introduced African dung beetles so far established in northern Australia.

Biological control of the dung breeding cattle pest, the buffalo fly, H. irritans exigua, is one major objective of the CSIRO Australia dung beetle program (Waterhouse 1974). The search for biological control organisms has been conducted primarily in regions of southern Africa that historically have supported substantial bovine populations, where the species diversity of the dung fauna is much greater than that in Australia (Bornemissza 1976, 1979; Doube 1985) and that have a climate similar to the areas occupied by the buffalo fly in Australia. Identification and selection of species with the potential to augment the biological control already acting in Australia will be facilitated by an analysis of the biological control potential of the dung fauna from both continents. H. irritans exigua does not occur in southern Africa (Zumpt 1973), but its ecological and biological counterpart is the African buffalo fly Haematobia thirouxi potans (Bezzi). This is being used as a model species to identify agents from the African fauna with the potential for biological control of dung-breeding Haematobia flies (Fay and Doube 1983).

If H. thirouxi potans is to be used for identification of predators with the potential for control of the immatures of H. irritans exigua, it is necessary that the predators respond similarly to both fly species. Here we present data on the predatory performance of the mite M. peregrinus on the immature stages of both species of buffalo fly and demonstrate that this predator responded similarly to each prey species.