Data on adults reared in the laboratory from eggs and larvae collected from cotton fields indicated that changes in seasonal species composition inHeliothisoccurred during the period from 1963 to 1979 in the delta of Mississippi. In the mid-60s, the population was predominantlyH. zea(Boddie). In 1969, it changed to a predominantlyH. virescens(F.) population and continued essentially as anH. virescenspopulation through the 70s. In 1979, the population changed again to become a predominantlyH. zeapopulation. Adults reared from both eggs and larvae followed this pattern. The data also indicated that in most years a higher percentage of the adults reared from eggs than from larvae wereH. virescens.