A stand of fully mature Quaking aspens (Populus tremuloides) add a majestic touch to the south fork of Bishop Creek in the Sierra Nevada range. This tall, fast growing tree typically reaches an average height of 80 feet, propogating through root sprouts as clonal colonies. Each colony therefore is its own clone, and any particular colony is viewed as a single ecological organism. Diebacks of these trees has been attributed to wildfire suppression and grazing, both of which seem to interfere with the root resprouting.

This is a Tussock Moth caterpillar, but I'm not sure which one. There are quite a few Tussock Moth species, including the banded, spotted and milkweed. I have a feeling this is the Milkweed Tussoc Moth (Euchaetes egle). If so, it only eats Milkweed, in the process absorbing cardiac glycosides that are retained through the adult stage. In other words it becomes poisonous to birds and other predators, and the bright colors and fierce look remind them of this.