The goal of these experiments was to determine if the increased longevity characteristics of our genetically selected long lived line of Drosophila could be attributed to metabolic differences. The data shows an inverse relationship between life span and temperature for both the long lived (L) and normal (R) strains; however, the higher longevity of the L strain relative to the R strain is not affected by these treatments. Therefore, the genetic factors unique to the L strain do not affect the same processes affected by the temperature treatments. A second set of experiments detected a linear relationship between the MDMR (mean daily metabolic rate) and the ambient adult temperature. However, at each temperature, the MDMR of either strain was statistically equivalent; a finding which demonstrates that an increased life span depends on something other than conservation of calories. A third set of experiments looked at the metabolic efficiency of the two strains and were not able to detect any statistically significant differences. The two strains appear to expend approximately equivalent numbers of calories per day in an approximately equivalent manner. These data are interpreted in the context both of a previously postulated genetic switch mechanism believed responsible for initiating the onset of senescence, and of contemporary reinterpretations of the "rate of living" theory which implicates the essential role of various anti-oxidant defense systems.