About 190 million screw flies later, South Florida appears to be free of the flesh-eating pest that threatened to wipe out the planet’s last remaining herd of tiny Key deer. The U.S. Department of Agriculture will release its final sterile fly to combat an infestation confirmed in September, which marked the first outbreak in the continental U.S. in three decades. About 135 deaths in a herd numbering just 875 were blamed on the insect — formally known as the New World screwworm fly — although the numbers could be higher since the herd is spread across such a wide area that also includes remote back country. the USDA’s Animal and Plant Health Inspection Service chief veterinarian called the massive effort a success, despite the flies getting a head start.