Physiological and morphological parameters that affect survival were measured at the individual level in adults of the lesser mealworm Alphitobius diaperinus kept at 6 °C and 10 °C. Survival differed significantly among individuals and sexes and at different temperatures. At 6 °C, pervasive effects of cold, i.e. chill injuries, were too strong to allow survival, whereas the duration of survival was significantly influenced by the adult body size at 10 °C; initial fresh mass was positively correlated with survival in both sexes. The management of energy reserves was also significantly different among individuals. Weight loss was significantly slower in both males and females that had the longest longevity and kept at 10 °C when compared to males and females that had shortest longevity (3.05±0.47 μg/mg fresh weight/day and 2.71±0.60 μg/mg fresh weight/day, respectively, vs 5.68±3.77 and 9.01±9.39 μg/mg fresh weight/day). The largest insects lost weight at a constant but slower rate than the smallest ones. Prolonged exposures at 10 °C enforced inactivity and led to depletion of the energy reserves in both males and females through low food availability. The water ratio was significantly decreased over time: both males and females that had the longest longevity had significantly lower water ratio than males and females that had the shortest longevity.