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.