SURVIVAL AND REPRODUCTION OF MUSCA VETUSTISSIMA WALKER (DIPTERA: MUSCIDAE) AND A SCARABAEINE DUNG BEETLE IN DUNG OF CATTLE TREATED WITH AVERMECTIN B1

Dung was collected 1, 2, 4, 8 and 11 weeks after cattle were treated in the prescribed manner for nematode control in the spring with either an injection of 200 μg kg^‐1 of avermectin B1 or a drench of levamisole hydrochloride. The avermectin B1 treatment affected survival of the bushfly, Musca vetustissima Walker, and breeding of the introduced dung beetle, Onthophagus binodis Thunberg. No bush flies survived from egg to adult in dung collected from animals treated with avermectin B1 2 weeks earlier, but survival rates returned to normal 8 weeks after treatment. Adult survival of O. binodis was not affected in dung of cattle treated with avermectin B1 but oviposition was reduced and immature survival was zero in dung from animals treated one week previously, returning to normal 8 weeks after treatment. Dung from cattle treated with avermectin B1 in summer and autumn would influence beetles little because most are not breeding then, but in spring when beetles are breeding the risk of harmful effects could be reduced by using an alternative treatment such as levamisole hydrochloride.