How do homopterans use their mouthparts to feed on plant sap?

Homopterans are specialized plant feeders that utilize a highly adapted, piercing-sucking mouthpart structure to extract sap from their hosts. The feeding mechanism is centered on an elongate, segmented beak known as the proboscis, which acts as a protective sheath for four threadlike stylets: two mandibles and two maxillae.1

When feeding, the insect inserts these stylets into the plant tissue. The mandibles are responsible for the initial piercing of the plant, while the two inner maxillae fit together to create a specialized sucking tube. This tube contains two distinct channels: one for the intake of plant sap and another for the secretion of saliva. By using this dual-channel system, homopterans can efficiently draw nutrients from the plant while simultaneously managing the chemical environment of the feeding site. Because they often ingest more sap than they require, they frequently excrete the excess as a sugary substance known as honeydew.12