How are heteropterans different from homopterans in the placement of their beaks?

The placement and mobility of the beak are key anatomical differences between heteropterans and homopterans.

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 or dorsoventral portion of the head.12

These differences are further supported by structural variations in the head and thorax: in heteropterans, a hard bridge called the gula separates the mouthparts from the prothorax. In homopterans, the gula is typically small, membranous, or absent, which allows the base of the mouthparts to abut or even fuse directly to the prothorax.3