Subject: My yard had no worms, then suddenly it did. Where did they come from?

My new neighborhood was built on top of heavy clay soil with no 
vegetation to speak of. I could find no earthworms at all. I amended the 
soil, planted stuff. A few years later I started finding earthworms. Where 
did they come from, especially since all my neighbors had the same 
absence of worms? Do they migrate large distances? Thanks. I couldn't 
find an answer to this in your database, except to learn that they don't just 
form out of nothing.

Re: My yard had no worms, then suddenly it did. Where did they come from?