Stellar mass versus oxygen abundance (upper panels) and the residual oxygen abundance (lower panels) as calculated from the best-fit M-Z relation for the field sub-sample (solid black line). The sample is divided between field, non-Virgo galaxies (left panels, solid blue circles) and those galaxies residing in the Virgo cluster (middle panels, open red circles). Mean metallicities in bins of fixed stellar mass (right panels) show no systematic difference between the field galaxies (blue squares) and Virgo cluster members (red triangles). Error bars show the 1-σ scatter in each bin.