The chromosomal locations of genes encoding these two CsIV proteins, i.e., P44 and P12, were also consistent with the symbiogenesis hypothesis. In fact, the ORF encoding P44 is not found in proviral DNA. It is notable that no ORFs encoding orthologs of P44 or other structural proteins such as MCPs are found in any of the other three ichnovirus genomes sequenced -TrIV, GfIV, HfIV [8, 14] . Therefore, this indicates that the orthologs of ichnovirus MCPs and other virion structural proteins are also probably located in the genomes of these wasps, i.e., not in proviral DNA. In contrast to this, we found that the gene encoding the CsIV ortholog of SfAV1a ORF061 is located within the proviral DNA. Whether ortholog proteins are similarly involved in the TrIV, GfIV and HfIV biology, their genes are not found in proviral DNA, since no matches were detected in their viral genomes. The phylogenetic analysis performed previously on P44 and the SfAV1a ORF061 orthologs [15] indicated that they have an ancestor close to that of the ascoviruses and iridoviruses.