Polymerase chain reaction amplifications of genomic DNA in 17 individuals of bisexual and parthenogenetic populations of three subspecies of Bacillus rossius (Insecta Phasmatodea) revealed that the species still harbours the whole variability of the ancestral Bag320 satellite family, since monomers of all non-hybrid Bacillus taxa plus private sequences occur in it. Bag320 monomers had not been rescued as a major satellite component in B. rossius, but possibly represent the remnant of a set of diverging sequences present in the Bacillus ancestor. Following the library hypothesis, these monomer variants have been differently amplified along the evolutionary pathways leading to present taxa in agreement with the mitochondrial phylogeny of the genus. The putative converted tracts observed are explained as the results of past gene conversion events.