Agriculture officials are working hard to stop the spread of screwworms that are threatening endangered key deer in Monroe County. Officials showed reporters boxes that each hold 76,000 sterile male flies. Once released, their job is to trick females into thinking they have mated. Because the male flies are sterile, the females stop breeding and do not lay new eggs."We do this rain or shine for as long as it takes to eradicate this," John Welch, from the U.S. Department of Agriculture, said.Officials said the eggs produce the flesh-eating parasite, which has killed 117 key deer in Monroe County.The parasite attacks animals through open wounds and feeds on its flesh.