The following descriptions of new species of black flies are based on material acquired from several sources in the Division of Entomology. The largest collections were made by field parties engaged in the Northern Insect Survey, a project commenced in 1947 and conducted by the Division in co-operation with the National Defence Research Board. Much of the simuliid material accumulated by this survey still remains to he examined and it will be several years before the valuable data on species distribution that it contains can be assembled into a form suitable for publication. Several collections of northern material have also been contributed by officers of the Household and Medical Entomology Unit. The rest of the material is the outcome of rnp own field studies in the Ottawa district, These studies, comnenced in 1949 and still continuing, are on a much smaller scale than the northern work and are designed chiefly to increase my knowledge of the group and to verify or supplement certain aspects of the work done by Twinn (1) in this area.