1920 males and females of Glossina palpalis gambiensis were fed 3 times on a Zebu treated with Flumethrin Pour-on. This resulted in a significant increase of the mortality and abortion rate of the flies. The fly-specific effects of Flumethrin Pour-on were time-dependent: Clear effects on the performance of the flies were observed during the first 20 days after treatment of the Zebu; an initial 90% "knock down" effect decreased to 40% during the first 15 days.