A few countries recycle manure by feeding it to larvae of the house fly (Musca domestica, adult shown here) and then using the larvae as an ingredient of animal feed. Because they can spread pathogens, however, house flies have been avoided most everywhere else. The black soldier fly (Hermetia illucens), on the other hand, is not a disease threat and so is widely approved as a recycling agent. The U.S. Food and Drug Administration approved its use in 2018. But the house fly deserves the same status as a tool for recycling animal waste, some researchers say. (Photo by Chelsea D. Miranda, Ph.D.)