They've taken over the world.
Seriously, I can't get rid of these guys. I haven't figured out what their eggs look like or where they're coming from. And nothing seems to slow them down. Every time I go out there are more and more and when I try to sneak up on them they fly away. They're especially in love with the squash plants. Geez. [Click pics to get a good look at this guy.]
This site has some great suggestions for getting them under control. I'm going on the offensive next season.
According to them, these beetles retreat and migrate according to the weather. They'll head south when it gets cold.
The problem last year is that it didn't get cold enough and they hung around. Which means they've multiplied through several generations, which is why there are so darn many here now.