In summary, we have attempted to define several points that argue for a different species name for the Wolbachia in nematodes. Until the endobacteria in the genus Wolbachia are formally characterized, typed and named according to the Bacteriological Code (Lapage et al., 1992), we believe that there is enough evidence to support naming, for purposes of discussion, the Wolbachia of supergroups C and D after a key host species in each supergroup, e.g. 'Wolbachia volvulus' (Onchocerca volvulus) and 'Wolbachia malayi' (Brugia malayi), respectively. The endobacteria of Mansonella spp., in Wolbachia supergroup F, which have both nematode and arthropod hosts, should remain W. pipientis until more study clarifies their phylogeny. By assigning different names to Wolbachia of the C and D supergroups, their unique biology and phylogeny will be better highlighted and the taxonomy of Wolbachia will be more in line with the biology of these fascinating bacteria.