When Vasilis Rodovitis rips open his brown paper bag in a sunny persimmon orchard just outside Naousa, in Greece, I half expect groceries to spill out. Instead, a barely there gray cloud emerges. For half a week, the bag was home to some 4,000 Mediterranean fruit flies (Ceratitis capitata). The thumbnail-sized flies, which the scientists here simply call "Medfly," quickly disappear into the orchard.