As the saying goes, there are many possible reasons for an insider to sell a stock, but only one reason to buy -- they expect to make money. So let's look at two noteworthy recent insider buys.

At Quidel, a filing with the SEC revealed that on Monday, CEO Douglas C. Bryant purchased 5,000 shares of QDEL, for a cost of $165.30 each, for a total investment of $826,500. Quidel is trading up about 1.1% on the day Tuesday. Before this latest buy, Bryant purchased QDEL at 3 other times during the past year, for a total investment of $2.85M at an average of $189.82 per share.

And at Beyond Air, there was insider buying on Thursday, by Director Robert Carey who purchased 15,000 shares at a cost of $6.67 each, for a trade totaling $100,050. Beyond Air is trading down about 8.1% on the day Tuesday. Bargain hunters can pick up XAIR even cheaper than Carey did, with the stock trading as low as $6.03 in trading on Tuesday which is 9.6% below Carey's purchase price.

For MarketNewsVideo.com, I'm Sayoko Murase.