Host odour composition affects host location efficiency of tsetse (Diptera, Glossinidae)

Abstract. Marked Glossina pallidipes Austen were released downwind of an odour source in the field in Zimbabwe and the percentage recaptured at the source on the same day was measured.In the absence of odour, 1.3% of the marked tsetse released from a box or refuge were recaptured, independent of the distance between release point and odour source.The distance was varied from 10 to 100 m.When natural ox odour or a blend of carbon dioxide, acetone, octenol and phenols was dispensed, untransformed recapture percentages of box-released tsetse decreased from 18% for tsetse released at 10 m to 2% for tsetse released at 100 m.Recapture percentages were significantly higher than in the absence of odour at all release distances for ox odour and for release distances up to 75 m downwind for the artificial odour.When a combination of acetone, octenol and phenols or carbon dioxide on its own was dispensed, recapture percentages decreased from 6% for tsetse released at 10 m to 0% for tsetse released at 100 m.With these odours, recapture percentages were higher than in the absence of odour when tsetse were released at 20 m from the source, but were lower than recaptures in the presence of ox odour or the artificial mixture with carbon dioxide.Recapture percentages of flies spontaneously leaving refuges were higher than those of box-released tsetse.Proximity of source had no effect on the recapture percentage of refuge-leaving tsetse and host-location efficiency was close to 100% when host odour was detected at 30 m or less.The results are discussed in relation to the host location strategy of tsetse.