Carbohydrate metabolism in flight muscle of the tsetse fly ( Glossina) and the blowfly ( Sarcophaga)

1. 1. Estimations of the glycogen content of blowflies and tsetse flies confirmed earlier observations that only minute amounts of carbohydrates could be detected in the latter, although considerable amounts are present in the former. 2. 2. The activities of enzymes involved in carbohydrate breakdown in the supernatant fraction of homogenates of flight muscle of both insects have been determined. In the case of trehalase, phosphorylase, phosphoglucomutase, glucosephosphate isomerase, phosphofructokinase and aldolase, activities were found to be considerably greater in blowfly than in tsetse fly muscle. 3. 3. Considerable trehalase activity was detected in the mitochondrial fraction of blowfly flight muscle, but none was detected in the case of the tsetse. 4. 4. No glucose-6-phosphatase or fructose-1,6-diphosphatase could be detected in either insect. 5. 5. Succinic dehydrogenase activity in the mitochondria was found to be similar in the two insects. 6. 6. The findings outlined above are consistent with the hypothesis that the energy required for tsetse flight is derived from different metabolites than in the case of most other Diptera.