We came back to a host of ants trouping into the house--a troubling problem, until you figure out where they're coming from.
But I found them! In my compost heap. I turned over the soil and they were everywhere, transporting their little white eggs to safety in a flurry of activity. So there goes my untreated compost, because I doused them with "organic" bug spray. I don't think I'd believe that "organic" thing in the U.S., but I definitely don't here. Supposedly it breaks down after a while, so we won't get two heads if I grow kale in that soil later.
The problem is that the ants mean business here. They just take over the whole garden until I go after their nest. My adding to the compost is, in effect, just feeding time for the ant colony.
Sometimes (when you see thousands and thousands of ants swarming, for example) a good bug spray feels like the way to go--even if one is fundamentally opposed to chemical sprays as a rule.