We describe here the cDNA sequence and mRNA expression of a novel family of the antioxidant protein, peroxiredoxin, from the firefly, Pyracoetia ruin. The 555 bp cDNA sequence codes for a 185 amino acid protein with a calculated molecular mass of approximately 21 kDa. The deduced protein of P. rufa peroxiredoxin gene contains two conserved cysteine residues. Alignment of the deduced protein of P. rufa peroxiredoxin gene showed 71.1% protein sequenceidentity to known insect Drosophila melanogaster peroxiredoxin. Northern blot analysis revealed that the P. rufa peroxiredoxin is specifically expressed in the fat body of P. rufa larvae.