Why are insects attracted to light at night?

about the episode

If you sit outside for a while in the summer and a lamp or candle is burning somewhere, it often doesn’t take long before the bugs start coming. But why these insects do this, often in completely hysterical flight patterns, has been a mystery for 2,000 years.

Researchers now believe they have solved this mystery, thanks to making a number of high-tech holograms. In preprint they first reject a number of existing theories.

Do insects use light to navigate? no. They could see this from their position relative to the light source, which was constantly changing. Are they keeping away from the heat then? Well no. Because the lamps in the experiments hardly gave off any heat. Are they blind? No, because they fly in patterns and not blindly. Are they trying to find their way out of the darkness, like escaping from a dark cave? No, the researchers say, and then they fly straight at it.

what is it then? According to the researchers, the images show that the insects use light to keep their bodies upright. In nature they use the glowing sky for that. In artificial light, they are just confused. They can fly around the light source and thus always correct their posture. Sometimes it’s so bad, for example when the light comes from below, that they fall or bump uncontrollably.

The theory is not new, but it has not been argued convincingly before, Kamiel Spoelstra, researcher at the Netherlands Institute for Ecology, responds in de Volkskrant.

The hope now is that the findings can help develop artificial light that has a less drastic effect on the insect’s rapidly declining population.

You can find the paper here: Why do flying insects congregate in artificial light?.

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