* Hartford shares hit all-time low, close at $9.62

* Cost of insuring Hartford debt rises

* Prudential stock drops 18 percent

(Recasts, adds new information on costs to insure Hartford debt, updates share prices)

By Lilla Zuill

NEW YORK (Reuters) - Shares of Hartford Financial Services Group Inc (HIG.N: Quote, Profile, Research) plunged nearly 52 percent on Thursday, a day after the property and life insurer posted a much larger than expected quarterly loss, stoking concerns it may need to raise even more capital to survive.

The share decline brought Hartford's market value down to $2.9 billion, not much more than the $2.5 billion that German insurer Allianz SE (ALVG.DE: Quote, Profile, Research) agreed to inject into the company earlier this month.

Chief Executive Ramani Ayer told investors late Wednesday that the third quarter was the worst in the insurer's 198-year-old history. Hartford lost money mainly from bad investments in financial companies.

"I honestly missed the degree to which markets have cratered," Ayer said late Wednesday.