In most terrestrial and aquatic habitats, the vast majority of animals transmitting and receiving communicative signals are arthropods. This book presents the story of how this important group of animals use pheromones, sound, vibration, and light for sexual and social communication. Because of their small to minute body size most arthropods have problems sending and receiving acoustic and optical information, each of which have their own severe constraints. Because of these restraints they have developed chemical signaling which is not similarly limited by scale. Presenting the latest theoretical and experimental findings from studies of signaling, it suggests that close parallels between arthropods and vertebrates reflect a very limited number of solutions to problems in behavior that are available within the confines of physical laws.