By David Russell, reporter at OptionMonster.Aflac ( AFL) surged after second-quarter results topped analysts' forecasts , prompting at least one big trader to write insurance on the stock. OptionMONSTER's tracking systems detected heavy selling of the November 35 puts. The options were priced at $2.50 to $2.65 and volume totaled 5,144 contracts, almost four times open interest. Most of the activity occurred in a single minute, indicating activity by an institutional investor. Aflac rose 6.7% Thursday to $37.81 and is up 22% in the last month. The supplemental insurance company would have to fall below roughly $32.50 for the put seller to lose money on the position. Other investors purchased calls to express a bullish sentiment toward the stock. The August 39 calls changed hands 2,031 times, rallying from 45 cents to a high of $1.20. The August 38 calls traded for 55 cents to $1.73. Volume exceeded open interest in both strikes. Overall options activity in Aflac was more than three times average on the session.