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In this study the influence of four systemic acting macrocyclic lactones on cattle-dung-inhabiting insects (Coleoptera and Dipera) was tested in summer 2000 in Berlin. Four groups of cattle were treated with the recommended doses of moxidectin, ivermectin, doramectin and eprinomectin in pour-on-formulations. One group of cattle remained nontreated as control. Dung from these groups was collected before treatment and 2, 5, 10, 15 and 20 days after treatment. Dung pats of equal size and volume were formed and placed on pasture. 0, 3, 7, 14, 21, 35, 49 and 63 days after deposition samples were taken and put in a plastic box to let the insects emerge. All Coleoptera and Diptera emerging within 28 days were collected and identified. The results of this study show that none of the macrocyclic lactones has an influence on the number of Coleoptera emerging from the dung pats. But residues of all four substances in dung pats from day 5 after treatment seem to reduce the emigration of Diptera. The varying dipterian family composition depends on the days pats were deposited on pasture. In general it was observed that the colonisation of dung pats by insects depends to a large extent on climatic and other environmental factors.