刺吸式口器昆虫在长期的进化过程中形成特殊的口针结构，用于专门吸食植物韧皮部筛管细胞的汁液成分。以蚜虫为例，它们在取食过程中分泌的胶状唾液和水状唾液将有效的降低植物防御反应，其中水状唾液包含的大量酶类不仅可以帮助蚜虫穿刺植物韧皮部，刺探到筛管细胞，同时也是植物感受蚜虫为害的激发因子，诱导出植物防御反应和相关抗性基因的表达。一般来说，蚜虫通常诱导植物水杨酸(SA)防御途径，但也有证据表明茉莉酸/乙烯(JA/ET)途径也参与了蚜虫诱导植物的防御反应过程，而蚜虫会采取反防御策略避开并适应植物的诱导抗性，使植物forisome蛋白失活，进而持续的在取食位点吸食汁液。由此可见，刺吸式口器昆虫的唾液分泌物将在昆虫与寄主植物互作关系中发挥重要作用。

         In the course of long term coevolution with their host plants, phloemsucking insects have evolved a special stylet that facilitates feeding on phloem sap. Using aphids as an example, we investigated the feeding mechanisms used by phloemsucking insects. Aphids secrete both viscous and watery saliva to reduce the resistance of their host plants during the feeding process. The watery saliva contains a complex mixture of enzymes that not only make it easier for the aphid to penetrate the phloem but which also appear to trigger the plant’s chemical defense mechanisms. Generally, aphids activate the plant’s defenses via the salicylic acid signaling pathway. However, previous research demonstrates that the jasmonic acid and ethylene signaling pathways are also involved in plant defenses against aphids. Aphids have evolved a variety of adaptations to counter plant defenses. For example, aphid feeding activity renders plant forisome protein inactive, thereby allowing aphids to continue feeding on their host plants. Our observations suggest that components of the saliva of phloemsucking insects are likely to play an important role in the interaction between herbivorous insects and their hostplants.