Biology of the red-backed cutworm, Euxoa ochrogaster (Guenée), was studied in the laboratory to provide new knowledge and for comparison with other cutworm species. The eggs possessed a moderately severe diapause that was terminated more quickly at 5 °C than at higher and lower temperatures. Intensity was related to temperatures of incubation. The eggs were fairly resistant to desiccation. The duration of development of embryos, larvae, and pupae varied inversely with temperature. A diurnal rhythm occurred in emergence of moths from pupae and during oviposition; more than 60% emerged and 85% or more eggs were laid during the night period. Moths mated in the dark. Multiple matings were common, ranging from one to seven and averaging two or three. Egg development at emergence was rudimentary but it accelerated with age after emergence. The preoviposition period in the laboratory averaged 8 days. The mean oviposition per female was 411 and ranged from 251 to 705. Maximum longevity of both sexes was approximately 20 days.