Caterpillar secretions and induced plant responses

Plants employ both direct inducible defenses (those that directly affect the physiology of the herbivore) and indirect induced defenses (defenses that attract or enhance the effectiveness of natural enemies of herbivores). During the last two decades, there has been a proliferation of studies showing that the oral secretions and saliva of herbivores play important roles in mediating inducible responses. Much of the study has centered on lepidopteran larvae (i.e., moths and butterflies) - no doubt due to their economic importance as agricultural pests, but also due to the relative ease of working with their secretions. In this chapter, I will not attempt a comprehensive review on the subject, but instead will focus this discussion on the secretions of larval Lepidoptera.