We live on the outskirts of Prescott, Arizona, in the forest, and at a slightly higher elevation than the town itself (around 6000 feet high). Anyway, my son found this caterpillar, and we were wondering what it is. I am providing you with two views, hopefully it will be helpful. Thanks!
Our first inclination would be that this was a Cecropia Moth Caterpillar, but you are west of the typical range. A western species in the same genus is the Ceanothus Silkmoth, Hyalophora euryalus. We searched online for a photo of the caterpillar, and found a site that substantiates our suspicions.
Columbia Silk Moth
(04/23/2007) Glover Silkmoth
While visiting your website, I came across one of the caterpillars you identified as Ceanothus Silkmoth. I thought the photo resembled the Glover Silkmoth, are they the same? I live in southern Arizona. I found a glover silkmoth and then began to raise them last year. Here are some photos of the Glover Silkmoths that I raised, one as a caterpillar and one of a male that recently hatched.
Glover’s Silk Moth, Hyalophora columbia gloveri, is a subspecies of the Columbia Silk Moth, Hyalophora columbia, which is found in Arizona. The Columbia Silk Moth is closely related the the Ceanothus Silk Moth, Hyalophora euryalus, which is not found in Arizona. Our identification of that caterpillar was based incorrectly on its range, cince the Ceanothus Silk Moth is found west of the Sierra Nevada Mountains and the Columbia Silk Moth ranging to the east. Thank you for sending us both the caterpillar and adult photo and correcting our earlier error.