It's been a little colder than normal here in Berkeley -- and as wet as the weather annals say we have a right to expect -- so ants are looking for warmer, dryer digs. They like it when you give them a little extra encouragement. An open sugar jar or compost container might attract an overnight bug invasion. And so might a smidgen of orange marmalade left over from breakfast.
It took a few hours, but the ants found that little bit of sugar, which had spread out into a nice globule on the stainless steel at the edge of our range top. They gathered around the marmalade like they were at a trough. There weren't a lot of them coming and going; mostly, this group found the good stuff and I think they were forgetting to run back and tell their pals about it.
Unfortunately, I have to acknowledge wildlife was harmed after I made this picture. I got a sponge and wiped up the marmalade and the ants with it. Their cousins are still around, though, scouting out the next feed.