The association of strong southerly winds with first spring captures of black cutworm (BCW),Agrotis ipsilon(Hüfnagel), adults in blacklight traps and captures of male BCW in traps baited with 40 μg of synthetic pheromone (3:1 ratio of Z-7-dodecanyl acetate:Z-9-tetradecanyl acetate) indicates that the first flight of BCW moths immigrate to central Iowa. This hypothesis is supported by the fact that all captured first-flight females are mated, a condition often associated with immigrating females. Additionally, a BCW development simulation model demonstrated the potential existence of two separate BCW populations, i.e., (1) immigrants and progeny, and (2) natives and progeny. We attribute low pheromone trap captures of BCW males and blacklight trap captures of mostly unmated females during the autumn flight to reproductive diapause in one or both sexes. We hypothesize further that a reproductive diapause might portend an autumnal southward migratory flight of BCW from Iowa.