Why are Insects attracted to light?

Why are Insects attracted to light?

Insects attracted to light because they think it is the Sun, 

or is it just that they use them as travelling reference points? 

Nobody really knows for sure, but moths/Insects are thought to use the moon as a point of reference to travel in a straight line. This might help to explain why more moths seem to be attracted to artificial lights on nights when there is no moon. If moths are drawn in very close to a bright light source they may become dazzled, due to their eyes being unable to adjust quickly enough to the sudden brightness, so will circle the light instead of flying away from it.