Bearish speculation is heating up on ON Semiconductor Corp. (NASDAQ:ONNN - 6.81), as traders increasingly opt for puts over calls on the chip stock. During the past five days, there have been 1,637 puts and 100 calls bought to open on the International Securities Exchange (ISE) and Chicago Board Options Exchange (CBOE), netting ONNN a put/call volume ratio of 16.37.

In fact, ONNN now sports a 10-day put/call volume ratio of 2.35 on the ISE, CBOE, and NASDAQ OMX PHLX (PHLX). This ratio ranks above 93% of other such readings taken during the last year, suggesting speculative players have bought to open puts over calls at a faster pace only 7% of the time.

Checking out the charts, ONNN has shed 11.8% of its value so far in 2012, and a recent rally attempt was thwarted by the stock's 200-day moving average. This benchmark trendline previously provided support for the shares, but could now switch roles to serve as resistance. Given this uninspiring price action, it's not too surprising to see traders shifting toward the bearish camp for ONNN.