The Mourning Cloak is a large butterfly native to North America. (Also native to temperate Europe & Asia). They prefer to feed on tree sap, especially that of oaks. They walk down the trunk to the sap and feed head downward. They will also feed on rotting fruit, and only occasionally on flower nectar.
North America - central Mexico. Woodlands. Flight: June-July. Host Plants: Black Willow (Salix nigra) but also other willow species, as well as poplar, elm, birch, and hackberry. Older caterpillars wander about and may be found on plants that they do not eat.