a1 Tsetse and Trypanosomiasis Control Branch, Department of Veterinary Services, P.O. Box 8283, Causeway, Harare, Zimbabwe
a2 Tropical Development and Research Institute, 56–62 Grays Inn Road, London, WC1X 8LU, UK
In the Zambezi Valley of Zimbabwe, the numbers of Glossina morsitans morsitans Westwood and G. pallidipes Austen electrocuted on grids placed across their flight paths as they arrived at various natural and synthetic odour sources demonstrated that ox odour comprises two broad fractions of attractants. One fraction can be trapped by a charcoal filter and, in part, consists of 1-octen-3-ol. A more volatile fraction passes through the filter and, in part, consists of carbon dioxide and acetone. Levels of acetone and 1-octen-3-ol in ox odour varied considerably, up to maxima of 24 mg/h and 0·025 mg/h, respectively. Catches were roughly doubled when octenol at 0·5 mg/h was added to ox odour, but declined when the dose was increased to 50–500 mg/h. A synthetic odour consisting of 2 litres of carbon dioxide/mm, 5 mg of acetone/h and 0·05 mg of 1-octen-3-ol/h, was nearly as effective as ox odour for G. m. morsitans but only half as effective as ox odour for G. pallidipes. Increases to the doses of each attractant in the synthetic odour increased the catches, to roughly double those with ox odour. Data for other Diptera are also presented.
(Received July 06 1984)