Required for the formation of intervein tissue of the wing. Acts in a dosage-dependent manner to suppress wing vein formation and promote development of intervein cells. Might play a role in the proper formation and maintenance of the trachea. After germ band retraction, high levels of zygotic expression are observed in a distinct subset of peripheral tracheal cells distributed throughout the embryo and low levels in somatic muscle. Expressed in the future intervein tissue of the wing imaginal disk from the third instar larvae until eclosion of the adult fly (at protein level). Expressed both maternally and zygotically.