On arriving at Nsazi Island on Victoria Nyanza in July 1918 to carry out some experiments with Glossina palpalis and rinderpest, I was at once struck by a marked diminution in the numbers of the fly on this and the neighbouring islands. Since the days of the first Commission of the Royal Society, the small island of Kimmi, about three-quarters of a mile N.E. of Nsazi, has been noted for the numbers of its tsetse. I had with me some of the original Mpumu fly boys and others who had worked on these islands with Fiske and Carpenter from 1911 to 1916. Their evidence on such matters is reliable, as they receive a bonus for their catches. They were all unanimous that the fly on Kimmi, Nsazi, and Tavu Islands had decreased very markedly in numbers. My own observations confirmed this in each case.