San Pedro River Valley, SE of San Manuel, Pinal County, Arizona, USA August 11, 2011 Size: approx 4 cm
I believe this is a Staghorn Cholla Moth Larva - Hodges#9308 (Euscirrhopterus cosyra); many adult moths also present in the evening, on a Jumping Cholla Cactus; elev. 2800 feet