Found in Oakhurst CA in the Sierra National Forest. White flea-like grasshopper with feathered tail .
Your insect is the nymph stage or young of one of the planthoppers. In the nymph stage it is hard to tell which one it is as they tend to all look alike. Once you see an adult then we know for sure.
Planthoppers feed on juices from shoots and leaves of plants, mostly trees and shrubs. The nymphs are known by the waxy filaments that stick out the back end. These nymphs (nor the adults ) do not feed enough to be pests.
They do look like wooly aphids, but are thicker bodied and have that long waxy tail.