plants are clever, and over the course of evolution they’ve learned that simply killing a pest outright is not necessarily the smartest strategy. Since a lethal pesticide would quickly select for resistant members of the pest population, rendering it ineffective, plants have evolved subtler and more devious strategies: chemicals that instead mess with the minds of animals, confusing or disorienting them or ruining their appetite—something that caffeine, mescaline, and morphine all reliably do.
