Pheromone trap catches of the Nantucket pine tip moth, Rhyacionia frustrana (Comstock), are often much higher during the first generation as compared with later generations, regardless of population density or damage levels. One hypothesis proposed to explain this phenomenon is reduced adult longevity during summer due to high temperatures. In this study, adult male and female moths placed in containers in the field during each generation showed significantly shorter life spans during the summer months compared with spring. Life spans were inversely related to the average number of daily degree-days accumulated during the investigations. In the laboratory, adult male moths under varying temperatures and constant humidity showed life spans similar to those observed in the field. Adult male moths that were provided with a sugar water solution in the laboratory did not have significantly longer life spans than those without. Male and female pupal weights showed little variation between generations and sites, and no observable changes in pupal weights occurred during the overwintering period. Some differences in female pupal weight between generations were found at some sites but these differences were not correlated with differences in adult life span. Temperature appeared to be the predominant factor affecting adult moth life span between generations, although other environmental and physiological factors may be important. An understanding of the lower trap catches for R. frustrana during summer may have important implications for using pheromone traps to predict population levels.