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

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)

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

Other answers:

How can I get my salt water pond to not stink so badly when the water level is low?

How do you care for an orchid?

Plants for my front yard?

Garden lillys how do i look after and tender them?

My tomatoes are stil green , any tips for riping them soon?

what is the effect of sodium chloride on the buddleia shrub?

How can I bring a dead olive tree back to life.?

i have moss on my Japanese maple branches - should I remove it?

I requirement assist identify a plant surrounded by my patio. I reckon it may be a full-size vine or a small shrub. It is brown green