Determination of the site in the cell of an imaginal disc-derived wing at which a prehair initiates outgrowth. Restriction of prehair initiation to the distalmost part of a cell is essential to ensure that each wing epithelial cell produces one adult hair that points distally. [ http://www.ncbi.nlm.nih.gov/pubmed/8947551 https://www.worldcat.org/search?q=bn%3A0815340729 ]