What are the catepillars that drop from oak trees? They turn into moths. How long do they live?

Question

This happens twice a year, early and late summer. This year was especially bad...thousands of the catepillars...hence thousands of moths. I'm in Marin county, just north of San Francisco. The trees are live oaks. I want to get rid of them but I don't like to use poison. (I will, though)

Answer 1

Silk worms. They are a nuisance but no real threat.