My husband and I have been using the fly predators around our barn for years. It is recommended that you buy them in three different batches at a month or so apart, but we've always bought just one batch in the spring and that takes care of our fly problems in and around the barn. You really can hardly even see them. They're no bigger than gnats, but once you put them out you notice that the fly population really diminishes and they can be used in many more places than just around a barn. Dog lots are a popular place to use them. Or anywhere that seems to be a breeding ground for flies.
