Observation notes: Found on a gaura plant in cool, clear weather. Another much smaller caterpillar is next to it, presumably the same species but perhaps a week younger. At dusk last night (when first spotted), I put a mesh sleeve over the plant to protect them from birds, at which point the caterpillar pictured reared up and waved its front half back and forth, although didn't move from the stem on which it sat. This morning at about 9am, I removed the mesh to photograph and better ID, and the caterpillar didn't move at all.
Verified by: Josiah Gilbert
Verified date: June 06, 2017
Coordinator notes: Actually this is indeed a White-lined Sphinx larva.