One thing about evolution — you never know what’s going to influence it. Take the European corn borer, for instance. Researchers have just made a strong case that a certain aspect of its behavior has evolved because of human harvesting of corn. The corn borer, Ostrinia nubilalis, is a pest caterpillar that spends spring and summer feeding on its host corn stalk before spinning a cocoon for the winter. It is almost identical to a related species, O. scapulalis — in fact, until recently the two were thought to be one. But O. scapulalis’s host plant is not corn, but a weed known as mugwort. In a paper in The Proceedings of the Royal Society B: Biological Sciences, Vincent Calcagno, a biologist now at McGill University, and colleagues show that, behaviorally, that makes all the difference in the world. For mugwort is neither harvested nor grazed, while corn has been harvested for centuries.