Does light attract flies? Yes, if the light is bright enough for them to see it. Flies can see very well in the dark (they generate their own light sources). It’s not clear why they are attracted to light, but one theory is that there are different types of cones in their eyes that react to different wavelengths of light. For example, people perceive green and yellow wavelengths as bright whereas red ones appear dimmer; this extends beyond human vision an into the ultraviolet range (i.e., insects do not need any additional assistance seeing UV-A or UV-B lights).