EFFECTS OF INGESTED IVERMECTIN ON BODY-MASS AND EXCRETION IN THE DUNGFLY, NEOMYIA-CORNICINA

Adults of Neomyia cornicina (F.) given continuous access to cow dung containing ivermectin at concentrations of 0.5, 0.25 and 0.125 mu g g( -1), the range found in the dung of injected cattle (Sommer et al., 19 92), were monitored every 12 h for changes in mass and excretory rates over a period of 3-5 days. Compared with the control insects, adult f emales that had ingested ivermectin showed disrupted patterns of daily mass change, an increase in dawn mass, and greatly reduced rates of e xcretion. Flies fed continuously with dung containing ivermectin at 0. 25 mu g g(-1) and 0.125 mu g g(-)1 in a regime identical to the above showed significantly increased abdominal mass compared with the contro ls. The observations are discussed in relation to other known effects of ivermectin on insect physiology.