Northern Prairie Wildlife Research Center
This caterpillar changes colors as it develops and molts. Mid instars are the most brilliantly colored with nine pairs of dorsal yellow spines, the first three pairs with partial to complete black rings; a middorsal yellow spine on A8; two rows of lateral blue spines tipped with white along T1-A8; white-tipped blue spines also occur on the head, at the base of the true legs, and in the anal region; body ranges from green to white-green. Later instars white-green with white spines. This species is common on snowbrush and bitterbrush during July and August.