Question: Why are flies so hard to swat?

Tatiana Trantidou answered on 17 Jun 2015:

This is because flies have developed an amazingly effective defence mechanism when they are in danger. In less than one hundredth of a second, the fly’s tiny brain calculates the location of the threat (the flyswatter probably), comes up with an escape plan and places its legs and wings in an optimal position to get out of the way in the opposite direction. All these happen so quickly, that scientists required three high-speed cameras to capture it.