Last year, on August 5th, I visited the area of the Moose Pond accompanied by my sons-in-law from Ontario and California, Fred Schueler and Gary Rathbun. Gary noticed a large caterpillar on an alder tree. Just yesterday, when I was organizing my pictures, I encountered a photograph taken at that time. I decided to send it in to E Fauna for an identification and today, I had my answer! It was identified as a Ceanothus Silk Moth (Hyalophora euryalus). The adult moth is very large, 89 to 127 mm, or 31/2 to 5 inches! This larva was about the length of an alder leaf but may have been not yet fully grown. The moth occurs from Baja California to Prince George. It feeds on various trees and bushes.   See: https://en.wikipedia.org/wiki/Hyalophora_euryalus