A colony of Leptocera caenosa (R.) was self-sustaining for 60 generations in a variety of organically rich media. With a wet larval medium of green grass meal and expanded mica in equal volumes at 17 °C the life cycle was completed (female to female) in an average of 31 days (egg stage, 2 days; larval and pupal periods, 13 days each). Green grass meal was superior to a standard cereal house-fly medium (CSMA) and legume leaf meals; a low coumarin strain of sweet clover was superior to a high coumarin strain. A non-sterile nutrient solution was also successfully used. In one sample of fresh alfalfa meal the pupal period was about 2.5 times longer than that in grass meal, possibly because of the presence of an estrogenic hormone.The species survived a 3-month exposure to 7 °C but not 1.5 °C, indicating that it could not readily survive out-of-doors during the winter in Saskatchewan.