The caterpillar is also known as Masked Birch Caterpillar, for one of its host species, birch. It also feeds on alder, which is where I found it in Larose Forest. This is quite a small caterpillar, and during the day it seeks shelter in a folded over leaf. When I spotted it, it was in a silken shelter on top of a leaf. As I tried to photograph it, it crawled out of the shelter. To see the adult (moth) it becomes: http://www.pbase.com/laroseforest/image/108713729