For a very thorough explanation of how synonyms arise the following publication is essential reading: Blackwelder, R.E., 1967. Taxonomy. John Wiley and Sons, Ltd. New York. i-xiv, 1-698.
Does someone has a scan of Nartshuk E.P. 2003. Key to families of Diptera (Insecta) of the fauna of Russian and adjacent countries. Proceedings of the Zoological Institute Vol. 294: 1-252 for me?