Detailed methods used for stock colony preparation, emigration assessment with density dependence checking, field study sites and comparison of the timescale at which the evolution experiments were done and the timescale at which the natural environment is changing from A sink host allows a specialist herbivore to persist in a seasonal source

This ESM contains the detailed description of (1): the approach used to establish the stock colony; (2): detailed experimental setup for measuring emigration as dispersal via wind; (3): the effect of density on the probability of dispersal; (4): a map of sampling localities during field surveys; (5): the comparison between the timescale at which the evolution experiments were done and the timescale at which the natural environment is changing.