Attempts to measure the influence of dung beetles (Coleoptera: Scarabaeidae) on the field mortality of the bush fly Musca vetustissima Walker (Diptera: Muscidae) in south-eastern Australia

The immature stages of Musca vetustissima Wlk. in dung pads in south-eastern Australia suffered a high mortality through the actions of a complex array of dung organisms, including dung beetles (scarabaeids), predatory beetles (hydrophilids and histerids) and predatory mites ( Macrocheles glaber (Mull.)). At times of high dung beetle numbers, it was possible to demonstrate a relationship between fly mortality and dung beetle numbers. Single-species dung beetle populations appeared to be as effective as multiple-species populations in reducing fly numbers, except that some benefit was derived from a combination of day- and night-flying species. When dung beetle numbers were low, their influence could not be measured because of the high mortalities already caused by the other dung fauna. It is suggested that in those circumstances any mortality caused by the dung beetles may simply have become substituted for an existing mortality caused by other fauna without adding to the total mortality.