The biting midge Culicoides variipennis (Coquillett) was the most common biting fly collected attacking cattle in Colorado in 1976; it comprised 62% of the collections and 6 species of mosquitoes totaled 33%. Concurrent New Jersey light trap collections supported the predominance of C. variipennis; it comprised 63% of the female biting flies collected for the species shown to attack cattle in this study.