A population ofLaspeyresia pomonella(L.) established on apples was compared with one from walnut as to the longevity of moths and oviposition capacity of females in relation to developmental condition of larvae (diapause vs. nondiapause) and to the weight of pupae. Comparisons were made with field collected material and among populations reared from 1st–3rd generations in the laboratory and after 12 generations. There was no difference in longevity between walnut and apple races nor between moths from diapausing and non-diapausing larvae, with the exception that moths from field collected diapausing larvae of the walnut race were short-lived. Variability sharply reduced as the populations adapted to laboratory conditions. Male moths lived longer than females, and isolated moths longer than paired sexes. Longevity was directly related to pupal weight, with a more pronounced response in males. Oviposition was lowest by moths from field collected diapausing larvae. From 57–80% of the populations were lost in the process of adapting to the laboratory, e.g., females from field collections which did not mate. Variability in oviposition was reduced in adaptation to laboratory rearing. Oviposition/female was related to pupal weight in both strains and both strains had equivalent pupal weights. However, laboratory reared moths of the walnut strain oviposited 49 more eggs/moth than the apple strain.If there is no correlation between mating adaptation under laboratory conditions and oviposition capacity, it may be concluded that the walnut strain had a higher reproductive potential than the apple strain.