Metabolic rate affects adult life span independently of developmental rate in parasitoid wasps

Developmental time and body size correlate with lifespan in a wide range of taxa, although not in insect parasitoids. When the rate of development is independent of adult metabolic rate, adult lifespan is free to adapt to the adult environment. We suggest that interspecific variation in intrinsic adult metabolic rates, differences in allocation of lipids to longevity, and reproduction and differences in the ability to use carbohydrates as an adult should all result in variation of adult lifespan, independent of development time. To test these ideas, we measured metabolic rate, lipid content and egg load at eclosion, developmental time, and lifespan of females with and without carbohydrate food in five species of Asobara, which represent parasitoids of Drosophila. No relationship between development time and adult longevity was found. As predicted, metabolic rates varied between species and appeared to trade off with adult longevity. We found no clear link between initial egg load and the longevity of a species, suggesting that lipid allocation may be less important in determining adult lifespan. The results obtained indicate that differences in metabolic rate have an important effect on adult lifespan, without affecting developmental rate in parasitoids.