1. Caged females of Rhyacionia buoliana attract males only during a limited period in the early evening. Outside this time no flying males could be observed. 2. Even when abdominal extracts of females are offered during a period of 24 hours, flight activity of males occurs only between late afternoon and beginning darkness. 3. Males could be attracted by abdominal extracts before females released scent and before the general male flight started. 4. On clear evenings extracts placed on aisles attracted males later than those in plantations. This difference in timing is explained by differences in light intensity between the two areas.