The rearing of Drosophila fruit flies at a temperature 5–7°C lower than the standard level until day 13 (or day 22) of the imaginal period enabled an increase of the individual insect lifespan. The positive effect of the longest exposure was evident in all age groups. This effect was due to prolongation of the initial period of the individuals’ lives and the subsequent delay of the onset of later developmental stages. The observed phenomenon may result in delayed development of aging-related pathology and a significant increase in the object’s maximal lifespan. The effect was independent of sample size (in samples of 100 to 1200 flies) and the interval between the experiments. All individuals of the cohort are assumed to contribute to the phenomenon.