Secretion of Two Types of Saliva by an Aphid

Abstract

NEARLY all phytophagous Hemiptera, including aphids, secrete a salivary material which coagulates rapidly on ejection to form a ‘stylet-sheath’ enclosing the path of the stylets in food materials and even in agar gel¹ and liquids². It has been reported³ that some Heteroptera secrete in addition a separate watery and water-soluble saliva which is emitted and sucked back both on the surface of substrates and within them. However, opinions differ on whether jassids secrete one type of saliva from which water-soluble substances diffuse before it gels⁴ or two distinct types of saliva⁵; and among the Homoptera generally, only a sheath-forming secretion has hitherto been demonstrated conclusively.