Flight activity ofEuxoa ochrogaster(Guenée) was monitored with BL traps for 2 years in Jefferson County, Oregon. Stages of egg development were determined from a random sample of females collected in the traps during the same period. Flight activity started in mid-June and ceased in mid-September, a period of 13–14 weeks with a peak near the end of July or early August. Weekly dissection of females from trap collections showed little or no egg development prior to early August, 4–5 weeks after adult activity began. However, eggs were present in the ovarioles during August and early September which is probably closely correlated with oviposition.