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How do homopterans differ from heteropterans in the position of their beaks?

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homopteran Newly emerged adult cicada (*Neotibicen pruinosus*).

The primary distinction between homopterans and heteropterans regarding their mouthparts lies in the origin and mobility of the beak.

In heteropterans, the beak arises from the front of the head and is movable. Conversely, in homopterans, the beak is fastened rigidly to the head, cannot be moved, and appears to arise from the ventral margin or the dorsoventral portion of the head.12

Furthermore, the structural integration of these mouthparts differs significantly between the two groups. In homopterans, the gula—a structure that typically separates the mouthparts from the prothorax—is small, membranous, or absent. This reduction allows the base of the homopteran mouthparts to abut or even fuse to the prothorax, a functional specialization not found in heteropterans, which possess a hard, distinct gula.3