Trap by trap, agricultural inspectors are casting a statewide net in an urgent hunt for a tiny bug with a voracious appetite that is threatening California's multibillion-dollar grape industry. Their prey: the European grapevine moth, an insect that has destroyed some vineyards in Europe, the Middle East and Chile -- and turned up in the Napa Valley in October. It was the first time the pest has been found in the U.S. Nobody's sure how it got here.