This huge cat at 51.5 mm was crossing the trail up to Garnet Peak, elevation about 5000'. I assume it is a mature cat.

It is somewhat similar to Hemileuca electra caterpillar http://bugguide.net/node/view/351710, but it is much larger, heavier and the hairs are much smaller and tighter. Possibly it is a later instar? Or a different species? My San Diego County moth list includes two other Hemileucas, nevadensis and eglanterina,two Saturnia's that seem smaller, and Hyalophora euryalus. I'm grateful for any help.