This study was conducted to assess the reproductive potential of first- and second-generationRhopobota naevana(Hübner) females collected from a commercial cranberry farm and reared on field-collected foliage under controlled conditions. Between 90 and 95% of eggs laid by first-generation females hatched within 2 wk of oviposition, whereas most (80–95%) eggs laid by second-generation females entered diapause. In 1990, when cranberry plants were heavily fertilized with nitrogen, total fecundity of the two generations was similar. In 1991, when a minimal amount of nitrogen fertilizer was applied to the plants, first-generation females were more fecund than second-generation females, and diapause eggs laid by second-generation females were larger than nondiapause eggs laid by first-generation females. Ovarian maturation proceeded more slowly in the second generation than in the first. Duration of pupal stage, adult stage, and emergence period were longer in the second generation than in the first. Male pupae weighed less than female pupae, and males emerged slightly before females. Results suggest that first-generation fireworm females allocate resources gathered during larval feeding to production of as many eggs as possible, whereas second-generation females produce fewer, larger eggs. However, second-generation females fed nitrogen-rich foliage may be able to produce more eggs than usual.