Why Are Some Moths Attracted by Lights?
Moths are attracted to lights at night because they mistake them for the light of the moon which they use as a means of navigation. These other lights confuse the moths and make them lose their sense of direction.
In trying to keep the artificial light at the same angle as the moons they circle it and come closer. Collectors use this behavior to trap moths with a special electric bulb which gives off light rich in ultra-violet rays. The insects are extremely responsive to these rays. But they cannot see red or yellow. So by using a red light you can watch them feeding at night without disturbing them.
It’s an important question for entomologists and other ecologists, who often collect moths using ‘light traps’. Of the hundreds of thousands of moth species, many don’t gather around lights. We tend to notice those that do, especially when they self-immolate. Even these differ: some spiral inwards, others head straight, but then orbit. The time of night and moth’s gender also make a difference.
Alternatively, moths may head skywards towards natural light, to escape predators or before high-altitude voyages. Once close to a bright light, moths probably become blinded, disorientated or confused by optical illusions (called ‘Mach bands’) that seem to show safe darker areas near the light’s edge.