Bearish speculation spiked on Herbalife Ltd. (NYSE:HLF - 37.34) in Wednesday's session, with put volume ramping up to roughly 55,000 contracts -- or six times the stock's typical daily put activity. Meanwhile, only about 20,000 calls were traded on HLF during the course of the session.

Front-month expiration is now just two days away, and opportunistic bears used HLF's December-dated options to place their bets against the shares. The most popular strike was far and away the December 35 put, where 11,156 contracts were exchanged. The majority of these puts traded at the ask price, suggesting they were purchased, while implied volatility on this soon-to-expire option surged a whopping 51.3 percentage points. Open interest at this strike rose overnight by 4,889 contracts, suggesting quite a few of these puts were freshly bought to open.

Traders bought those HLF December 35 puts for a volume-weighted average price (VWAP) of $1.21, so the stock needs to fall below breakeven at $33.79 in order for bears to turn a profit. Based on Wednesday's close at $37.34, that's a drop of more than 9.5% -- and, as noted earlier, the shares have just two sessions left to live up to these pessimistic expectations.

After checking out the stock's daily chart, it's easy to see why bears bombarded HLF on Wednesday. The shares plummeted more than 12% by the closing bell, hammered by reports that fund manager William Ackman is actively shorting HLF. The intraday drop was drastic enough to trigger a short-selling halt, leaving put options as the bearish vehicle of choice for traders.

However, HLF was already a popular target for pessimistic players ahead of that massive mid-week drop. Short interest on the stock rose by 36.6% during the past two reporting periods, and now accounts for a substantial 19.5% of the equity's float. At HLF's average daily trading volume, it would take more than eight days for all of these shorted shares to be unwound.