Why are moths attracted to light?

A moth circling a lightbulb.

Nobody really knows for sure, but moths 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.

Answered by Phillip Rispin, Curatorial assistant of Etymology at The Manchester Museum.