Abstract: The two non-pollinating fig wasps on Ficus hispida L.， Philotrypesis pilosa and P. sp.，might share the latest common ancestor. Host plant recognition using olfactory system by fig wasps may act as a strict pre-mating isolation mechanism. We investigated the introns of the atypical olfactory receptor gene Or83b-like，which is remarkably conserved among many insects and can be used to unveil speciation and the direction of differentiation in closely related species. The PCR results showed that the nucleotide identity in the coding regions and the identity of the deduced amino sequences between the two fig wasps were 98.2% and 99.03%，respectively，and that of the introns 84.5% on average. The high identity further confirms the close relationship between the two fig wasps. However，inter- and intra-individual length-variant heterozygotes in some introns in P. sp. were observed， but not in P. pilosa. It is so inferred that P. pilosa might have become stable as a species，while P. sp. may be still in the process of speciation.

Key words: Hymenoptera, non-pollinating fig wasp, Or83b-like gene, intron, length-variant heterozygotes (LVHs), evolution