Northern Prairie Wildlife Research Center
Splendid black-brown to gray twig-mimic bedecked with barklike coloration and warting. Color highly variable. Head dorsoventrally flattened, held forward, antennae long. Second thoracic segment thickened with broad subdorsal swellings. First abdominal segment with oblique swelling in front of and below spiracle; second segment with smaller rounded wart in same position. Proleg on sixth segment often with black line that continues onto preceding segment. Dorsum of fourth and fifth abdominal segments with paired knobs; eighth abdominal segment slightly raised. Caterpillar of yellow slant-line (T. crocallata) with U-shaped mark extending upward and about vertex. Food: many deciduous trees, as well as pines and hemlocks. Caterpillar: June to November; 2 generations in North.