EFFECT OF AVERMECTIN RESIDUES IN SHEEP DUNG ON MATING OF THE AUSTRALIAN SHEEP BLOWFLY LUCILIA-CUPRINA

Male and female Lucilia cuprina adults were separated after emergence and then fed either dung excreted from sheep after an oral treatment w ith ivermectin (Ivomec(R)) or non-treated sheep dung. Fresh dung (non- treated or ivermectin-treated) was collected daily and fed to adults f or 6 days after drenching. After this feeding period, males and female s from each feeding treatment were paired and all aspects of mating be haviour recorded. Feeding on avermectin residues by adults had a signi ficant effect on two components of mating: (1) males fed on ivermectin -treated dung directed less mating attempts at females compared with m ales fed on non-treated dung; (2) mating duration by males fed on iver mectin-treated dung was longer compared with males fed on non-treated dung. There was no significant difference in the level of sexual recep tivity (percentage mating) between females fed on either ivermectin-tr eated dung or non-treated dung, although subsequent oviposition by fem ales fed ivermectin-treated dung was significantly delayed. Both femal e and male mortality was significantly greater when feeding on ivermec tin-treated dung compared with non-treated dung. The effects on mating , when coupled with the deleterious effects on ovarian development and adult mortality, demonstrate the potential for avermectin usage in a control strategy against L. cuprina.