As shown in Figure 6, communication among three plants via VOCs was found here for the first time. This plant communication occurred especially when the second receiver plants were exposed to T. urticae-induced volatiles emitted from VOCos-receiver plants for 1 day. These results clearly suggest that VOCos-receiver plants have two potential means for the priming of defense responses, i.e., by interacting with herbivores’ enemies and with neighboring conspecific plants by releasing a VOC blend. Although we do not know the ecological consequences of such multi-plant communi- cation, plants may have evolved this system that allows plants to emit and respond to volatile cues in order to sustain their population built up of genetically identical plants. This view is supported by recent findings indicating that communication is more effective between branches that are genetically identical than between branches that are genetically different [31]. Nevertheless, it was reported that resistance-inducing volatiles of lima bean move over distances at which most leaves that can receive the signal still belong to the same plant [25]. Therefore, VOC signals that are responsible for communication between individuals are also required for coordination among branches within a single plant [7,24,32]. Future studies should provide considerable insight into the factors that enable a volatile communication system in individual plants and their population.