Abstract
High mortality was observed in tsetse flies, Glossina morsitans morsitans, that had had a single blood meal on rabbits which had previously been administered tetracycline complex salts. The death of the flies was apparently effected by the killing of the fly symbionts and the destruction of the mycetomes of the gut. It is suggested that tetracycline complex salts in the food or drink of livestock may be tried for the control of tsetse flies.