Field trials to examine overwintering potential ofPlathypena scabra(F.) in central Iowa were conducted with moths and pupae in the winter of 1968–1969, and with moths only in the winters of 1971–1972 and 1972–1973. No survival was ever obtaincd in field cages containing the insects. Cabinet trials were conducted with pupae at temperatures of −17.8, −3.9, 4.4, 12.8, and 26.7°C. At −17.8°C, 100% mortality occurred in 7 days. Pupae tested at −3.9°C had 100% survival after 8 days, 40% survival after 13 days, and 0% survival after 33 days. Pupae at 4.4°C survived 45 days without mortality, but all were dead after 90 days. A 12.8°C constant temperature lengthened the pupal stadium to 28.1 days and caused 20% mortality. Mortality at 26.7°C was only 6.7%, and the mean pupal stadium was 8.4 days.Supercooling-point determinations indicated that the larva was significantly more susceptible to cold temperatures, that the prepupa and adult were similar in response, and that the pupa was significantly less susceptible to cold temperatures than other stages.Temperature data were collected during the winter of 1971–1972 to determine the actual temperatures present in probable overwintering sites under litter. Supercooling data indicated that the larva was the least likely, and the pupa the most likely overwintering stage. Cabinet trials indicated, however, that the pupa could not survive the temperatures present during 1971–1972. The adult was shown in several winter studies not to survive. The conclusion is drawn, therefore, that it is unlikely that the larval, prepupal, pupal, or adult stages of the green c1ovenworm can overwinter in central-Iowa litter habitats.