A few years ago, right at the start of Summer, all of a sudden I had a ton of flies in my garage. I bleached, scrubbed and pressure washed every inch of the garage but couldn't get rid of the flies. Finally, I tried the old pennies and water in a zip-lock bag trick, and after a couple of days, the flies were gone. Was it just a coincidence, or did the zip-lock bag trick actually work? If it did work, why?