The present invention provides methods for synergistic control of ectoparasitic arthropods with a synergistically effective amount of a combination of the macrocyclic lactone moxidectin and an arylpyrrole compound. Also provided are methods of protecting animals from infestation and attack by ectoparasites with said combination. The present invention also provides synergistic insecticidal compositions comprising as essential active ingredients the macrocyclic lactone moxidectin and an arylpyrrole compound.