Plants and animals co-exist on sometimes precarious terms in the struggle to survive, and one creature’s food is another’s destruction. This program looks first at ants. Leaf-cutter ants can denude whole trees, whose leaf fragments they cart away to their hills and turn into compost; this provides food for mushrooms, which in turn feed the ants, who carry mushroom filaments with them when they emerge and thus help the mushroom to propagate—which is useful to the ants because the mushroom produces an antidote to the protective ant-poisons produced by the tree. But there are stranger alliances—ants that protect trees from other insects in return, as it were, for exclusive nesting rights; butterflies camouflaged to look like leaves so that they can feed and lay their eggs where heredity dictates; flowers that produce imitations of butterfly eggs to fool real butterflies into finding other places to deposit their eggs; flowers that grow in gardens cultivated by ants. (28 minutes)