An Editorial Expression of Concern was posted on 14 September 2017 (http://science.sciencemag.org/content/357/6357/1248.1), once the editors were informed of errors in the labeling and description of the control experiments described in figs. S1 and S2. In particular, in fig. S1, carmine should have been kermesic acid, and in the caption of fig. S2, carmine should have been carminic acid. After discussions with the authors and minor revisions to the manuscript and supplementary materials, including corrections to a few other minor errors in the text that do not affect the conclusions of the paper, the editors are now confident in the results. The Editorial Expression of Concern has therefore been removed from the PDF of the paper. The paper and supplementary materials have been corrected online.