Why are moths attracted to artificial light?

BBC Wildlife writer Henry Gee investigates an enduring wildlife mystery.


Mother Shipton moth © Stephen Farhall


That light attracts moths is proverbial. “Drawn like a moth to a flame” we say of people with irresistible urges to check out something risky. Except that not all moth species are drawn to artificial light, and for those that are nobody really knows why.

The general explanation is that the moths use a bright, distant light – the moon, say – as a navigation beacon, always flying transversely to it. However, artificial lights are closer than the moon, so the moths gradually spiral in to their doom.

But is that answer correct? Some experts have suggested that certain artificial lights resemble the frequencies of light emitted by the sex pheromones of female moths. Or that light attracts moths to settle down – after all, sunshine is a prompt for night-flying moths to call it a night. Or that very bright light simply disorients them.

Nobody knows for certain. It could be that each theory is true for different moths. After all, there are 160,000 known species with their own behaviour: the challenge is to tell the difference between moths and myths.

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