AbstractThe theory of the ‘gasterophiloid origin of the tsetse fliesxy’ advanced by Pollock (1971, 1973) is not warranted by the arguments presented in support of it. The traditional view that warble and bot flies are monophyletic, and that hence the ‘Gasterophilidae’ can be included as a subordinate group of the Oestridaes.l., remains unrefuted. The claim of Popham&Tenabe (1973, 1974) that no rotation occurs in the male postabdomen ofGlossinais er