There exists an incredibly cool insect whose habits I must share. It's called the green ant (or green tree ant). They make these cool complicated nests in trees out of branches and leaves, and they eat pretty much any caterpillar or other bug that happens across their path. But that's not the cool part.
There is also a kind of butterfly called a Lycaenid which, when it is a larva, produces a kind of honeydew from a gland on it's butt. This sweet fluid is rich in nutrients and the vicious green ants love it. The caterpillar also has two little glands that produce a soothing pheromone that chills out the ants and reminds them that this is a food-producer, not food. So the ants don't eat the caterpillar, they drink the honeydew-- and they protect the caterpillar from predators. They make him a little nest on the edge of their colony in the tree, and they make sure he gets enough to eat, and then when he's ready to turn into a butterfly, they continue to guard the pupa and they let the butterfly crawl out of the nest and fly off without hurting it.
Basically? The ants have dairy cattlepillars. How awesome is that?