The tobacco plant synthesizes nicotine to protect itself from herbivores. The female moth broadcasts sex pheromones to attract a mate, while a soldier ant deploys an alarm pheromone to call for help. The carbon dioxide on a mammal's breath beckons hungry ticks and mosquitoes, while a flower's fragrance speaks to the honey bee. Indeed, much of the communication that occurs within and between various species of organisms is done not by sight, sound, or touch, but with chemicals. From mating to parenting, foraging to self-defense, plant and animal activities are accomplished largely by the...