ABSTRACT
An investigation into the possible development of insecticide resistance in tsetse flies was carried out by comparing the susceptibility to topical applications of endosulfan and dieldrin between two populations of Glossina pallidipes Austen in Kenya; one from the Lambwe Valley, where there has been a long history of spraying operations, and the other from Nkruman which has never been sprayed. Dosage-mortality regression lines and LD data showed that wild-caught, non-teneral males and females from Lambwe were significantly more tolerant of both insecticides than their counterparts from Nkruman, with the exception of males dosed with dieldrin. The differences were insufficiently great, however, to be incontestable evidence for the development of resistance in the Lambwe strain, although there were no obvious sources of variability between strains adequate to account for the differences in susceptibility.
