Feeding is invoked in some way in almost all the encounters and associations between different species. The choice of food is immense: plants grow in a multitude of forms, from seaweeds to cactuses and from grasses to forest trees: animal prey is available from tiny krill in the oceans to antelopes on the plains. As almost every species is accessible to another with the right feeding strategy, there is a continual evolutionary jostling between eater...