Willows, including weeping willow, cottonwood and alder.
Young larvae feed in groups on the undersides of the leaves.
After a few days of aggregated feeding they separate and feed alone. They typically skeletonize the leaves and when the damaged leaf dries, it tatters in the wind, breaking off and leaving only the main vein. Adults also feed on the leaves. First generation damage can be serious on ornamental willows but is not of much concern on wild trees. Later generations seem to cause very little damage.