Impact of herbivore symbionts on parasitoid foraging behaviour

Parasitoids are insects that lay eggs in other insects, but before this, they have the remarkable task of locating and successfully attacking a suitable individual. Once an egg is laid, many herbivorous hosts carry defensive symbionts that prevent parasitoid development. Some symbioses can act ahead of these defences by reducing parasitoid foraging efficiency, while others may betray their hosts by producing chemical cues that attract parasitoids. In this review, we provide examples of symbionts altering the different steps that adult parasitoids need to take to achieve egg laying. We also discuss how interactions between habitat complexity, plants and herbivores modulate the way symbionts affect parasitoid foraging, and parasitoid evaluation of patch quality based on risk cues derived from parasitoid antagonists such as competing parasitoids and predators.