From what i have read the human eye cannot see UV reflective light on materials.We can only see UV reactive light on materials.When we shine a black light on materials and see them glow,this is UV reactive.
UV reflective do not glow.When UV light hit them it is reflected and becomes more visable to certain predators that are capable of seeing UV light.
Most feathers and many materials are UV reflective to some point.They work best in deeper water when colors fade.The UV light is reflected off the flies and are more visable to the fish than a fly that simply disappears in the dark..