Blacklight traps were placed in soybean fields in 3 central Iowa counties during late April and early May 1975. Traps were tended every third day, with the number and sex of the collected green cloverworm adults recorded. Females were dissected to determine the number of times each had mated and were classified according to their reproductive status.Green cloverworms showed a distinct seasonal variation in mating and reproductive status. Seasonal variation culminates in nonfecund females during autumn.Male green cloverworms were collected in greater numbers in blacklight traps than were females. The sex ratio was weighted toward males when the population numbers were at high levels.