part of continuous with adult head adult tracheal section adult labial tracheal branch It could correspond to pharyngeal branch. fly_anatomy.ontology FBbt:00003097 labial trachea Trachea of the adult head that results from the ventral tapering of the postgenal air sac. It extends down into the proboscis, with the maxillary palpus trachea splitting from it, and terminates in the labial muscles. adult maxillary palp tracheal branch postgenal air sac tracheal branch