This morning I went into my bathroom and there were ants wandering around. They hadn't formed a line yet, but there were maybe a dozen, moving around and exploring. I didn't see them in any other rooms; I couldn't find where they were coming from but I think it was probably under the floor.
I squished as many as I could see (and took the bathroom rug out and threw it in the wash), but when I came back, more had come; there were about the same number as the first time.
I squished them again; more came again.
Then I had a bright idea: I turned my Roomba loose in the bathroom and closed the door.
The next time I went in? No ants, living or dead.
I was pretty pleased with myself, until I saw the black widow spider in my shower, at which point I decided yeah maybe it is time to call an exterminator.