AbstractThe phylogeny of the cryptic species complex of wasps in the genusNasoniawas inferred by analysis of nucleotide sequences of an rDNA internal transcribed spacer (ITS2) and the D2 region of 28S rDNA. Phylogenetic analysis showed thatN. vitripennisdescended from a theoretical common ancestor with that of a lineage that diverged intoN. longicornisandN. giraulti.Differences in the ITS2 regions clearly distinguished two strains ofN. giraulti.Another member of theDibrachysGroup,Trichomalopsis dubius, was placed outside of theNasoniacomplex. The D2 region had a base substitution rate =2 times slower than the ITS2 region and was used to resolve the phylogenetic affiliation of an eulophid,Melittobia digitata, to the pteromalids. Tree topology of theNasoniacomplex was congruent with the phylogeny of a cluster ofWolbachiabacteria which infect these insects. The possible role of these bacteria in driving speciation is discussed.