Development of European corn borer larvae on Event 176 Bt corn: influence on survival and fitness

European corn borer larvae, Ostrinia nubilalis (Hubner) (Lepidoptera: Cramb idae) that have completed development on Event 176 Bt corn hybrids have sur vived exposure to sublethal doses of the Cry1Ab Bt toxin or are exploiting plant tissues that do not express the toxin. To evaluate the impact of such exposure, diapausing larvae were collected from Event 176 and conventional hybrids and compared for rates of pupation, parasitism, fitness (pupal wei ght, longevity, and fecundity) and susceptibility to the Cry1Ab toxin. Larv ae completing development on Event 176 corn exhibited approximately 10% hig her survival rates and correspondingly lower parasitism rates than larvae c ompleting development on conventional hybrids. No significant differences w ere detected in pupal weight, fecundity, longevity or susceptibility to the Cry1Ab Bt toxin. These results indicate that survival on Event 176 corn ar e not adversely affect fitness and does not cause increased tolerance to th e Cry1Ab toxin in subsequent generations.