First, we discuss the functionality of oral secretions of herbivores in the defense of plants, since plant damages are resulted from both herbivore mouthpart chawing ( or piercing) and oral secretions. 因为植食性昆虫取食造成的植物损伤是与昆虫口腔分泌物共同作用的结果,所以首先阐述口腔分泌物在防御反应中的作用。