Rate of development for larvae and pupae of orange tortix, Argyrotaenia citrana (Fernald), reared on artifical diet medium under field conditions varied significantly between winter/spring and summer experiments. Mean developmental requirements for male and female larvae and pupae were 481, 531, 178, and 168 degree-days (DD-5 degree C), respectively. In laboratory experiments, nitrogen content of various food sources significantly influenced survivorship and developmental rates of larvae. Estimated emergence of adults from several field sites in Oregon and Washington in 1983, 1984, and 1985 occurred 300-700 DD from 1 January. The 50% cumulative emergence ranged from 470 to 500b DD for males and from 520 to 560 DD for females. Cumulative emergence of an overwintering population heavily parasitized by the braconid Apanteles aristoteliae Viereck, was accelerated ca. 75 DD in 1983. Two peaks in weekly catch in pheromone traps occurred in caneberry fields with overwintering populations. The first coincided with peak male emergence, the second occurred after 750 DD and varied in magnitude relative to the first peak. In fields not harboring an overwintering population, catch reached a maximum during the second peak-time period, suggesting that immigration of males into these sites was influencing catch.