Pontia callidice - Peak White
This is a beautiful denizen of the high Alps. It is another restless butterfly, with fairly powerful flight, suitable for the conditions it lives in.
I once spent an inordinate amount of time following one around a parking area, it probably only settled twice in 30 minutes, whereupon it became absolutely invisible. I inevitably spooked it back into flight both times and never managed a butterfly photograph.
The male shown here did behave wonderfully, allowing the only close approach I have ever managed.