The aim of this study was to isolate the full-length cDNA sequences of an unusually highly conserved olfactory receptor (orthologue to the Drosophila melanogaster DOR83b) from the antennae of Spodoptera exigua and S.litura by using reverse transcription-polymerase chain reaction (RT-PCR) and rapid amplification of cDNA ends (RACE) methods.Bioinformatics methods were used to further analyze the cDNA sequences and putative amino acid sequences.The two full-length cDNA sequences from olfactory receptor (OR) of male S.exigua and S.litura were named as SexiOR2 and SlitOR2,respectively.SexiOR2 and SlitOR2 consisted of nucleotide sequence of 1906 and 2 483 bp,respectively,and both with deduced amino acid sequences of 473 residues.The sequence analysis indicated that the deduced amino acid sequences of the cDNA shared the high homologies with OR83b orthologue chemoreceptor sequences from previously reported moths,implying that the cDNA sequences were of OR83b orthologue chemoreceptor genes.