I'm not sure why a black butterfly would be called a 'White' Admiral - it must have to do with the white stripes on its wings.
This crisply attired beauty is extremely skittish and hard to take a picture of - unless it's busy with some puddling or getting the salts from a newly made hypertufa creation. The males especially are attracted to wet soil, carrion, rotting fruit and sap.
The black wings accented with broad white bands make this stand out among all others - there are few other really black butterflies.
Willows and birches are the host plants for the caterpillars which are quite grotesque, with a hump behind its head, and an unappetizing greenish yellow colour. Presumably, this is to resemble bird droppings, making it uninteresting.