The construction and use of several sizes of cages for experiments or colony rearing of the large milkweed bug, Oncopeltus fasciatus (Dallas), are described. Large adults are produced by a mean sunflower seed consumption of about 60 mg per bug, of which 1/3 is retained as dry body weight, and smaller adults by limiting consumption to about 30 mg per bug. Water consumption is of the order of 20% of live body weight per day at 30°C. Adults can be stored at 14°C for 3 months without food and for at least 5 months with an aqueous (SYE) solution of 50% (w/w) sucrose and 1.25% yeast extract, absorbed in polyester fleece. Survivors, restored to 30 °C with seed, produce enough viable eggs to maintain the colony; egg production is larger if the cold-storage period is shorter, but still lower than that of unstored colonies. First-stage nymphs can be stored for 2 months at 14°C on SYE; mortality is high but survivors grow and reproduce at 30°C on seed. Larger nymphs, like eggs, do not tolerate prolonged cold-storage. During 14°C storage there is little or no seed-feeding, mating, or egg production, but nymphs can still molt at least once. The sucrose intake rate is ca. 20—30 mg/g-day at 30°C but only % as great at 14°C. The rearing system described minimizes labor and various potential problems; frequent servicing is required only during the egg-production stage.