Walnut caterpillar

Woodlands, forest edges, and landscapes containing walnut, hickory, pecan, or butternut trees, especially in eastern North America.

Larvae feed gregariously on the leaves of walnut-family trees and may cause noticeable defoliation. Adults do not feed extensively and primarily reproduce.

Caterpillars cluster on foliage by day and may rear their front and rear ends when disturbed. They eventually descend to the ground, burrow into soil or leaf litter to pupate, and produce multiple generations in warm regions.

They are not venomous and generally pose no direct danger to people, though their hairs can occasionally irritate sensitive skin. They support birds and other predators, but heavy infestations can stress or defoliate host trees.