A Smelly Conflict: The Role of Olfactory Information in the Interaction of Insect Herbivores and Their Natural Enemies

ABSTRACT Chemical communication is one of the most fundamental ways in which insects interact with their environment. Many herbivores rely on olfactory cues such as plant volatiles to locate natural‐enemy‐free spaces for feeding or ovipositing; conversely, predatory and parasitic natural enemies detect herbivores by chemical cues from damaged plants or from the herbivores themselves. The role olfactory cues play in mediating insect behaviors as well as the molecular and neuronal mechanisms by which these infochemicals are perceived have been investigated in a wide range of insects. However, the questions of how certain infochemicals shape the interactions between herbivores and their natural enemies, and whether herbivores and their enemies might converge onto a similar olfactory perception space have not been answered. Here, we aim to address these questions on infochemical‐based herbivore‐natural‐enemy interactions by reviewing the chemical, molecular and neuronal basis of olfaction in herbivores and their natural enemies, with a focus on the behavioral defense strategy of insect herbivores against their natural enemies. Based on the reviewed findings, we suggest that herbivores and their natural enemies converge towards using specific olfactory cues. This olfactory specificity might help herbivores to avoid natural enemies and acquire host‐plant resources, but it also allows specialist natural enemies to home in on certain volatile cues for finding their insect victims.