part of prothoracic segment larval prothoracic segment larval segmental nerve prothoracic nerve larval prothoracic segmental nerve Larval segmental nerve of the prothoracic segment. Similar to the A1-A7 nerves, it has two roots, anterior and posterior, both formed from neurons of the same segment as the nerve (Campos-Ortega and Hartenstein, 1997). Proximally it shares a glial sheath with the intersegmental nerve before branching from it at the border between the prothorax and mesothorax (Campos-Ortega and Hartenstein, 1997). It receives sensory fibers from the ventral monoscolopidial chordotonal organ, Keilin organ and vc1 sensillum (Campos-Ortega and Hartenstein, 1997). It gives off a thick branch to the ventral intersegmental muscle, while its main branch continues to the ventral transverse musculature, the ventral Kolbchen and the vc2 sensillum (Campos-Ortega and Hartenstein, 1997). prothoracic posterior fascicle SN fly_anatomy.ontology VFB:FBbt_00002085 FBbt:00002085