The salivary secretions of a plant-sucking bug, Oncopeltus fasciatus (Dall.) (Heteroptera: Lygaeidae)—I : The types of secretion and their roles during feeding

Abstract

Oncopeltus secretes two types of saliva: sheath-material, which coagulates rapidly and forms a linging to the path of the stylets when the insect feeds on natural food materials; and a watery and water-soluble saliva, which is secreted and sucked back again both on the surfaces of substrates and within them. Dysdercus fasciatus Sign. (Pyrrhocoridae) secretes both types of saliva in a similar manner. In agar gels containing sucrose or homogenized peanut, Oncopeltus deposits watery saliva, some of which is sucked back several minutes after secretion. During this process, substances are leached from the medium and starch grains are broken down by an amylase. The course of feeding in both natural and artificial media is described. It is suggested that, once feeding has begun, the secretion of watery saliva is inhibited by the flow of liquids up the food-canal; that stylet-activity is inhibited by the presence of acceptable substances in these liquids, but cessation of the inhibition can be brought about by sensory adaptation; and that the secretion of sheath-material is elicited by resistance to the passage of the stylets, but the rate of flow is uncontrolled and only a limited amount can be secreted continuously. The functions of the salivary secretions are considered, with reference to the feeding of the phytophagous Hemiptera generally.