THE EFFECT OF DIET ON LONGEVITY IN CALLIPHORA ERYTHROCEPHALA MEIG

Life tables were constructed for three lines of C. erythrocephala Meig., under different dietary conditions. All the survival curves obtained from these tables followed the typically rectangular shape of an ageing population, except for males and females which had been reared from underfed larvae and subsequently given a sugar/water diet only. Whilst all flies could survive quite well on sugar/water only, the addition of protein (liver) to the diet significantly increased longevity in all cases. However, a liver/water diet only was found to be little better than water alone. Protein added to a sugar/water diet at the 60 per cent survival level increased longevity significantly (P < 0.001), although its action was not immediately apparent, and in about 30 per cent of the flies there was no improvement in survival. Liver added to a sugar/water diet at the 20 per cent survival level did not significantly alter the life span of survivors. These results are considered as supporting the threshold idea of ageing proposed by Maynard Smith (1962).