Flies have been a nuisance to humans for as long as they have raised crops and bred livestock, causing skin diseases and infections and carrying contagious diseases from one animal to another — or even to humans. Flies are so difficult to control because they are so prolific. Because flies reproduce so rapidly, chemicals have never been successful in controlling fly populations because they can mutate and produce pesticide-resistant offspring. Fly Parasites interrupt these prolific insects’ life cycle, breaking the chain. Each container includes 5,000 eggs.