Can. Ent. 103: 1323-1335 (1971) The phylogenetic relationships between species groups and subgenera in the Forcipornyiinae are presented for the first time, from a consideration primarily of male genitalic structures and comparative morphology of all stages. A dendrogram showing the phylogenetic relationships within the subfamily and a figure showing the evolutionary trends in claspette development in the subfamily are given. The genitalia of Atrichopogon are considered as plesiomorphic and the genus a possible living prototype of all Ceratopogonidae.