I used to have ants all over the place, especially the kitchen, because we always leave food around. About a month ago they disappeared. We could reliably attract several hundred ants in 20 minutes by opening a meat-lovers pizza on the counter. Oddly, they didn’t touch the veggie-lovers pizza right next to it. (Pretty good controlled experiment for a Y!Ahoo, huh?) But now we don’t a single ant on either pizza. The weather didn’t change appreciably. I’ve heard that in urban areas ants build massive underground colonies. Since the houses are so close together, is it possible that one of my neighbors killed all of my ants in the process of killing his own?