Techniques and equipment are described for feeding, in the laboratory, Cnephia invenusta (Walker), Simulium innocens Shewell, and S. rugglesi Nicholson & Mickel collected from exposed birds at the Seney National Wildlife Refuge, Seney, Michigan, and C. ornithophilia Davies, Peterson, & Wood, S. euryadminiculum Davies, and S. rugglesi reared from larvae at the Seney Refuge (S. rugglesi) and the Patuxent Wildlife Research Center, Laurel, Maryland. In 4 feeding experiments with C. invenusta on Pekin ducklings, 109 fed of 194 flies exposed; in 2 experiments with S. innocens on a mallard duckling and an Emden gosling, 35 fed of 65 flies exposed; in 12 experiments with S. rugglesi on mallard ducklings and Canada goose goslings, 465 fed of 1215 flies exposed; in 40 experiments with C. ornithophilia on Khaki Campbell, mallard, and Pekin ducklings and yearling Canada and Emden goslings, 950 fed of 1713 flies exposed; and, in 2 experiments with S. euryadminiculum on Pekin ducklings, 27 fed of 46 flies exposed. Feeding time varied from 2.10 to 15 minutes. C. ornithophilia, S. innocens, and S. rugglesi fed on Khaki Campbell, mallard, and Pekin ducklings and yearling Canada geese infected with Leucocytozoon simondi Mathis & Leger were held 4-7 days after the blood meal. The flies were triturated in physiological saline and deactivated calf serum and inoculated intravenously and intraperitoneally in parasite-free Pekin, Khaki Campbell, and mallard ducklings and Canada goose goslings. Birds became infected with L. simondi 9-14 days after being inoculated with C. ornithophilia; 4-7 days after being inoculated with S. innocens; and 9 days after being inoculated with S. rugglesi. Starved, laboratory-fed C. ornithophilia fed first on L. simondiinfected Khaki Campbell and Pekin ducklings, held 4-7 days at room temperature, then fed for the 2nd time on parasite-free Pekin ducklings, transmitted the infection by their bite. The birds showed young parasites in the peripheral blood 10 and 11 days following the 2nd feeding.