The obsoletus group of the subgenus Culicoides (Avaritia) is characterized and the four eastern North American species, which were previously included under the names obsoletus (Meigen) and chiopterus (Meigen), are described with keys for identification of males and females, and when known, the larvae and pupae. These four species are alachua n. sp. from Florida; chiopterus (Meigen) not abundant, probably widespread; obsoletus (Meigen) common and widespread; and sanguisuga (Coquillett), the important pest of eastern woodlands. The known distribution and breeding habitats of these species are discussed.