Why Are Insects Attracted To Light?

Anyone who has ever had a bug zapper has seen insects fly right into it. Insects naturally seem to be attracted to light. Why?

Actually, no one knows, but there are several theories.

One is that they aren’t as much attracted to light as they are disoriented by it. Many flying insects use light as a compass. When a light source is distant, like the sun, incoming light rays arrive about parallel to each other, so they expect to receive light at a fixed part of their eyes. Scientists call this “transverse orientation”. So everything looks normal as long as the insect flies in a straight line. But if the light is nearby, like a candle, the angle at which the light strikes the insect’s eye quickly changes even though it’s still flying straight. So the insect tries to adjust and keep a constant angle to the light, which means spiraling right into it.

Or maybe this is all about ultraviolet light, which we can’t see, but insects can. We know many flowers have patches of ultraviolet “color” to help attract pollinators, so insects may be confusing man-made ultraviolet light with a food source.

One more — it could be a matter of sex (isn’t it always?) A light’s infrared radiation may resemble the infrared reflection from moth pheromones – those chemicals used to attract mates.

I realize this isn’t the most pressing scientific mystery, but it is another example of how we can affect our environment.

For more information, see “Why are moths attracted to flame?” at https://earthsky.org/earth/why-are-moths-attracted-to-flame? . The photo came from that site.

Leave A Reply

Your email address will not be published.