The cocoon is oval, about 40 mm long and 22-24 mm in diameter, and white when first constructed. Color is somewhat variable but is commonly reddish brown. Near the margin of each wing there is a black line with a light border outside. The head is reddish brown and the body yellowish green or apple green. Each body segment bears six yellowish to orange tubercles armed with bristles.
Spiracles are red to orange.
Along the side of each of abdominal segments 2-7, there is a conspicuous slanted to nearly vertical yellow line. The last abdominal segment bears purplish-brown horizontal lines that form a V design at the rear. In the Auburn vicinity, new adults usually emerge in late July and early August and begin a second generation. Second-generation larvae complete development by fall and construct cocoons in which they overwinter as pupae. Among the oaks, sawtooth is a frequent host.