I live in the rural Midwest and in the last week our house has been invaded by a mass of 1-2" thin worms. They look like worms but upon close inspection, they actually have small antennae and legs.

They started out congregating on the cement stoop by our back door and up the door frame. Then I started finding them in our basement. Now today I'm finding them in our house.

First off, I'd like to know what they are and where they came from. Secondly, I'd like to know how to get rid of them. Preferably, I'd like to do something organic but if that's not possible, I'll gladly resort to chemical. I just want them gone!