Why do many galls have conspicuous colours? An alternative hypothesis revisited

Abstract

It has been proposed that the colour of many plant galls evolved as an aposematic signal to protect the contained gall-maker from attack by chewing herbivores. But the evidence would suggest the more likely hypothesis is that the colour is caused by the galler inducing the gall to senesce early, thus releasing nutrients from the dying tissues of the gall to the benefit of the gall-maker. External agents, like chewing herbivores or natural enemies of the gall-maker, may subsequently learn to use these colours as signals.