Hi Tim,
Just had a quick look in my book, and from your picture, i would say you are right with your "Cabbage White" conclusion.
They show a picture in my book that looks the same as your "critter" and it quotes them as "Velvety".
You are quoted as saying, "I am a lover of nature, it goes with the job"
Do you mind me asking, what do you do????
cheers stupo.