In this paper four new species of Phlebotomus are described, three from Africa and one from the Malay States, and the differential characters and affinities of seven other known species are described and illustrated. Three specimens, including one of P. minutus, Rond., and two of P. papatasii (Scop.), have been observed to possess supernumerary spines on the superior claspers: a remarkable and apparently hitherto unrecorded phenomenon in this genus. In several instances fresh data are given as to the geographical distribution of these insects, and an endeavour has been made to clear up some confusion with regard to certain closely allied species.