PIERIDAE
   
Pieris marginalis
This butterfly has been the subject of frequent 
  fluctuation of taxonomic opinion, with frequent changes of generic, specific 
  and English names. An extreme lumper would recognize just one species of wide 
  Holarctic distribution, under the name Pieris napi. A splitter would 
  regard the Nearctic and Palaearctic butterflies as distinct and would recognize 
  several North American species and subspecies. I follow current thinking in 
  calling the species on Vancouver Island Pieris marginalis. So many English 
  names have been used that it is perhaps best to stick to the scientific name. 
  The upperside of the butterfly is immaculate, even to the wingtips. The veins 
  on the underside may be more or less delineated with dark scales, or, as in 
  the butterfly photographed, not at all. Several foodplants in the family Brassicaceae 
  (Cruciferae) have been recorded. On Southern Vancouver Island I have found it 
  and reared it on Hesperis matronalis.