Accession number(s). All sequences described in this study have been deposited in GenBank. The 16S rRNA gene nucleotide sequences of the bacteria isolated from flies described in this study have been deposited under accession numbers MF370887 to MF370906. Described mcr-1 sequences have been deposited under accession numbers MF069152 and MF598564 to MF598566. Described mcr-2 sequences have been deposited under accession numbers MF580947 and MF580948. Described mcr-3 sequences have been deposited under accession numbers MF598567 to MF598572.