Upper panel: dust-to-gas mass ratios against metallicity for Virgo SFDs. Here we plot the oxygen abundance obtained from N2 e O3N2 indices for the whole sample. Solid line indicates a linear scaling of the Milky Way and metallicity, dotted and dashed lines correspond to a factor of 5 and 10 difference from MW, respectively. Lower panel: comparison data for KINGFISH and DGS samples. Here the metallicity of Virgo SFDs was derived using the R₂₃ ratio only for 13 objects with [OII]λ3727 line measurements available in the literature. A broken power-law fit (orange line) with a break at [12 + log  (O/H) ] _break = 8.36 and low-metallicity slope α = 2.23, is overlaid to the data. The dotted line shows the linear scaling of the dust-to-gas ratio of the Milky Way with metallicity.