Fluid-Feeding Mouthparts

The mouthparts of most specialized fluid-feeding insects consist of more or less elongated components forming a proboscis. Functional types of mouthparts evolved as adaptations to particular food sources. Characteristic feeding techniques are used which are based on a combination of capillarity and a pressure gradient created by sucking pumps. Biting-sucking mandibles occur in some predaceous insect larvae and are used for extraoral digestion. Lapping mouthparts evolved in nectar-feeding insects; such proboscises are characterized by a loose food canal and setose, pro- and retractable structures at the tip which take up fluids mainly by capillarity. In contrast, piercing-sucking proboscises have pointed components to penetrate the host’s epidermis. The elongated components are firmly interlocked to form a tight food canal and a salivary duct. Piercing-sucking proboscises ingest fluid along a pressure gradient and occur in plant sap-sucking insects, blood feeders, and predaceous species. Sponging proboscises are rather short and retractable. Their soft and cushion-shaped apical components take up liquids from open fluid sources. Siphoning proboscises are particularly long and primarily adapted for nectar drinking. Such sucking mouthparts ingest fluid into the food canal predominantly by a pressure gradient.