25.08.2020

Do you know why moths are attracted by light?

licht.de explains the appeal of light for nocturnal insects

Quickly airing the room in summer evenings without turning off the light can attract myriads of insects. Specially moths soon enter a spiralling path around the light. But why is that so?

Nocturnal insects like moths us the moon for their orientation. Keeping themselves in a certain angle to it helps them fly straight. This technique works because the heavenly light source is very far away. Artificial luminaires are closer and consequently during the insects´ flight their angle changes constantly. The permanent course correction ends in a spiral which takes the moth dangerously close to the light source and eventually makes it collide with it. Scientists call this explanation navigation theory – for it has not been finally clarified in detail yet.

Also the color of light affects the insects´ approach. Warm white light of LED attract less animals than for example mercury high-pressure lamps which nowadays are rarely used. Learn more in issue licht.wissen 20 “Sustainable Lighting”.

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