ERR1/ERR2 mutants progress normally through embryogenesis and first instar development, but die abruptly during the later half of the second larval instar with no obvious morphological defects. Mutants are severely metabolically compromised, with a 2-fold decrease in ATP levels relative to control larvae. Normal glycogen concentrations and elevated circulating trehalose concentrations are observed in these animals. TAG levels are decreased in these mutants. Variations in the levels of other metabolites is observed compared to control animals.