How do black bears respond to deer flies & horse flies?

This black bear is trying to slap a deer fly (in the white circle). Deer flies and horse flies bite hard. Bears shake their heads when these flies bite their faces or ears. In early summer when bears have short new fur, these flies can reach the skin and bite nearly anywhere. Black bears often try to catch them by slapping them like this or biting them out of the air before the flies can bite. They know they have to move fast to catch them. When a researcher offered a horse fly in his fingers, the usually slow-moving bear moved lightning fast to get the big fly before it could get away, using its lips and tongue with precise accuracy.