NEW YORK (MarketWatch) -- Energy stocks moved into the red on sustained worries about the economy on Thursday. The NYSE Arca Oil Index (XOI 942.00, -4.57, -0.48%) fell 0.3% to 944. The NYSE Arca Natural Gas Index (XNG 517.95, +0.18, +0.04%) fell fractionally to 518. The Philadelphia Oil Service Index (OSX 173.18, -1.24, -0.71%) dropped 0.7% to 173.
