Certain ant species "farm" plant lice, properly known as aphids. There is no exploitation in this process; it is a truly mutualistic relationship. In return for protection from predators, such as ladybirds, the aphids allow the ants to "milk" them for the sugar-rich honeydew released at the ends of their alimentary canals. The ants perform the milking by stroking the aphids with their antennae, which may look as they were tickling them.