The New World screwworm fly is threatening the $113 billion U. S. cattle industry for the first time in more than a half century, with an infestation from its flesh-eating larvae confirmed in south Texas. The infestation was discovered in a single 3-week-old calf in La Pryor, Texas, about 100 miles (161 kilometers) southwest of San Antonio and 50 miles (80 kilometers) from the U. S. -Mexico border. Federal and state officials had been working to keep the parasite from reaching Texas, home to 1...