Extrusion of a cellular projection from the apical membrane of an epithelial cell in an imaginal disc-derived wing. Outgrowth initiates approximately 35 hours after puparium formation from the distal side of the cell, and at this stage the cellular extension is termed a prehair. [ http://www.ncbi.nlm.nih.gov/pubmed/11064425 http://www.ncbi.nlm.nih.gov/pubmed/8947551 ]