The tobacco budworm, Heliothis virescens (F.), is thought to be a pest that migrates each year from warmer southern latitudes to colder areas where it cannot survive cold temperatures during the winter. Although northwestern Mississippi is south of 40° N latitude, which is recognized as the upper boundary for overwintering survival of the insect, it is commonly believed that increasing abundance during the spring in this area is because of migration of moths from the south. In this study we used a 10-year set of captures of tobacco budworm male moths from pheromone traps and air temperatures from the area, as well as data on development of tobacco budworm in incubators at a range of constant temperatures. Results indicated that moths that produced eggs before the 258^th day of the year have time to accumulate the necessary degree days to produce the last generation of that year, while moths that produced eggs between days 258 and 277 give raise to the first spring generation. Moths re productively active after day 277 will not, under the hypothesis of no larval overwintering survival, produce a generation the following year in northwestern Mississippi. Moths reproductively active between days 80 and 124 will produce the generation observed between days 136 and 162; there is a gap between generations, and this gap will separate generations all year. Because we observed generations overlapping in the data from the pheromone traps, there is a possibility that larval overwintering survival might explain the dynamics of the insect in this area.