Species of horse flies resembling Tabanus affinis Kby. and its allies with hairy eyes and red sides are among the abundant but taxonomically troublesome, North American Tabanidae, especially in the boreal regions. McDunnough (1921) did much to clarify the status of females of the most prevalent species, but omitted discussion of the scarcer males. Information on a few additional species and the availability of males of all species treated by him, make further discussion propitious at this time.