US STOCKS-Wall St dips in volatile trade; oil prices fall further
* Energy sector lower; banks, utilities big losers
* Petsmart to be acquired by private equity consortium
* Indexes off: Dow 0.6 pct, S&P 0.6 pct, Nasdaq 1 pct (Updates to close)
By Caroline Valetkevitch
NEW YORK, Dec 15 (Reuters) - U.S. stocks ended lower in a volatile session on Monday as oil prices extended their selloff, adding to worries about weak global demand.
The losses follow the S&P 500's worst weekly performance since May 2012. The index is now down 3.4 percent since Dec. 8 but is still up 7.6 percent for the year so far.
The S&P 500 energy index bounced between positive and negative territory but ended down 0.7 percent after U.S. crude settled off 3.3 percent at $55.91, hitting fresh 5-1/2 year lows. Both U.S. crude and Brent have fallen roughly 50 percent from highs in June.
"The question of lower global demand ... and how that translates into global economic growth, is a worry for investors," said Bucky Hellwig, senior vice president at BB&T Wealth Management in Birmingham, Alabama.
Utility and financial shares were also among the day's biggest losers, with shares of JPMorgan Chase down 1.5 percent at $59.16. Continuación...