These two were cavorting on the side of our house.
From Butterflies & Moths of North America
Hackberry Butterflies fly in a fast and erratic manner, and rest upside down on tree trunks. Males perch on tall objects in sunny areas to watch for females. Eggs are laid in clusters, and the young caterpillars feed communally. Caterpillars overwinter in groups gathered inside dead rolled leaves.
Caterpillar hosts are various hackberries and sugarberry.
Adult food include sap, rotting fruit, dung, carrion. They will take moisture at wet spots along roads and streams.
The habitat of Hackberry Emperors is wide - along wooded streams, forest glades and river edges, wooded roadsides, towns.
They reside in most of the eastern United States, central Plains states, and the southwest mountains; northern Mexico.