Here is a lesson that we’re going to be taught again and again in the coming years: Most animals are not just animals. They’re also collections of microbes. If you really want to understand the animal, you’re also have to understand the world of microbes inside them. In other words, zoology is ecology.

Consider the western corn rootworm—a beetle that’s a serious pest of corn in the US. The adults have strong preferences for laying eggs in corn fields, so that their underground larvae hatch into a feast of corn roots. This life cycle depends on a continuous year-on-year supply of corn. Farmers can use this dependency against the rootworm, by planting soybean and corn in alternate years. These rotations