Generally, stalls are cleaned often enough to prevent fly development in the stalls. We often see adult flies in stalls, as they like to come in out of the elements and are drawn to the opportunities to feed themselves. Fly breeding more often takes place outdoors in areas where we cannot clean as well and where decaying organic material will be around long enough to support development. However, if stalls are lined with heavy mats that cannot easily be cleaned under, you may want to add a small pinch of Fly Predators to a corner of the stall when distributing.