Another day of very heavy volume in the ETFs. 2.4 million puts traded in the SPYders (SPY) alone. 5.6 million puts and 3.3 million calls traded across all the exchange-traded funds, or more than 2X the recent average daily. The action started early with a block of 94K SPY May 110 puts traded at the 71-cent asking price. With SPY down $4.18 to $112.64, this contract now fetches more than $2 and is the most actively traded options contract, having traded more than 340000X Thursday. Other ETFs seeing 2X or more average daily volume include DIAMONDS (DIA), SPDR Gold Trust (GLD), iShares Emerging Markets Fund (EEM0, SPDR Retail Trust (XRT), Proshares Ultra Short S&P 500 (SDS), and the iShares MSCI EAFA Fund (EFA)