Why Do Flies Hover Round Lights?

Flies hover around lights because to insects, a bright light source is seen as an emergency beacon. When in doubt, they will instinctively head for the light, which is generally higher than their current danger-filled position. Moving towards the dark would be seen as a move downward, which can be even worse than not moving at all. Light for some insects could be viewed in the same way as air bubbles pointing the way up to the surface for other creatures.