I never thought about the flies, but I can tell you when I leave for work in the morning they are all lined up on the siding sunbathing for the day's energy. I worry about the bees stinging me when I take their meal away. We used to have some sort of dung beetle that got to the poop pretty quickly. Those were interesting to watch. I clean up at least daily if not more often in the summer when we are outside often.