Responses of Glossina morsitans morsitans Westwood and G. pallidipes Austen (Diptera: Glossinidae) to the skin secretions of oxen.

In Zimbabwe, catches of Glossina morsitans morsitans Westwood and G.pallidipes Austen at odour baited traps were increased in the presence of residues of a solution of the skin secretions of oxen (hereafter sebum) by 80% and 29% respectively, and catches at F3 traps were significantly increased when sebum was presented on adjacent screens. Testing of fractions of sebum revealed active components(s) in the phenolic and non-acidic fractions but not in the acidic fraction. Furthermore, the activity of the phenolic fraction could not be explained by the presence of the known phenolic tsetse attractants. The effect of sebum was to attract more flies to the target rather than to induce a landing response in a higher proportion of attracted flies. Whether or not tarsal contact responses are involved remains conjectural. However, targets that were electrified over only one quarter of the surface caught more than one quarter the catch of targets electrified over all the surface both with and without sebum, indicating that many tsetse habitually alight more than once on baited targets. Data on the catches of other Diptera are also presented