The S&P 500 closed slightly lower on Monday. Investors, meanwhile, focused on some notable insider trades.

When insiders sell shares, it indicates their concern in the company’s prospects or that they view the stock as being overpriced. Either way, this signals an opportunity to go short on the stock. Insider sales should not be taken as the only indicator for making an investment or trading decision. At best, it can lend conviction to a selling decision.