Western tussock moths everywhere

We have two big coast oaks in the yard, and there are lots more in the streets. Every one of them has thousands of western tussock moth caterpillars, many of them descending on the fine filament they spin. This one came in on the newspaper delivered to the front gate ..  

(Updated to fix the moth id; this is not an oak moth caterpillar, despite being on the oak tree .. )