Chemical signals mediate all aspects of insects' lives and their ecological interactions. The discipline of chemical ecology seeks to unravel these interactions by identifying and defining the chemicals involved, and documenting how perception of these chemical mediators modifies behavior and ultimately reproductive success. Chapters in this volume consider how plants use chemicals to defend themselves from insect herbivores; the complexity of floral odors that mediate insect pollination; tritrophic interactions of plants, herbivores, and parasitoids and the chemical cues that parasitoids use to find their herbivore hosts; the semiochemically-mediated behaviors of mites; pheromone communication in spiders and cockroaches; the ecological dependency of tiger moths on the chemistry of their host-plants; and the selective forces that shape the pheromone communication channel of moths. The volume presents descriptions of the chemicals involved, the effects of semiochemically-mediated interactions on reproductive success, and the evolutionary pathways that have shaped the chemical ecology of arthropods.