Mean bioluminescence time-series data from young (10-day), middle-aged (30-day) and old (50-day) flies in LD/temperature cycles (lights on at 25 °C and lights off at 21 °C). Bioluminescence CPS is plotted as average of raw counts at 60-minute intervals. Data are shown as mean ± SEM with error bars at each time point. 10-day cohort equals black lines and columns, 30-day cohort equals mid-grey lines and columns, and 50-day cohort equals light-grey lines and columns. (A) The 8.0-luc 50-day cohort shows higher PER amplitude and acrophase than 10-day and 30-day (p < 0.001 in all). 30-day is higher than 10-day in acrophase (p = 0.03) but not in amplitude (p = 1.00). (B) The XLG-luc 30-day and 50-day cohorts show lower PER amplitude and acrophase compared to 10-day (p < 0.001 in all), 50-day is lower than 30-day (p < 0.001 in both). (C) The tim-luc 50-day cohort shows lower TIM amplitude and acrophase compared to 10-day and 30-day (p < 0.001 in all), 30-day group is lower than 10-day in acrophase (p < 0.001) but not in amplitude (p = 1.00).