Mourning cloaks (Lepidoptera: Nymphalidae: Nymphalis antiopa) are among the first butterflies to be seen in the spring in North America. Although some individuals migrate south, most overwinter as adults and emerge when temperatures rise. I found this individual on the Greenstone Ridge at Isle Royale National Park on my visit there in May.
Once active the adults feed mostly on tree sap and rotting fruit, then mate and lay their eggs. Larvae emerge in the summer and eat leaves of trees in the birch (Betulaceae), willow (Salicaceae), and elm (Ulmaceae) families. On Isle Royale the abundant paper birch (Betula papyrifera, Betulaceae) and quaking aspen (Populus tremuloides, Salicaceae) were likely host plants.