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Night Lights

July 1, 2021

Fireflies are among the more pleasant features of a summer evening. Children chase them across the yard, and adults just enjoy their beautiful flashes.

But our own nightlights could be chasing them away. Recent work has found that artificial lights can interfere with the flashes, which are part of the mating ritual. That means fewer of these twinkling lights for future generations of children to chase.

In fact, research is showing that artificial light is a problem for all insects — not to mention professional astronomers and casual skywatchers. A study in Peru, for example, showed that insects were attracted to outdoor LEDs in droves. That made them easier for predators to catch, kept them from catching their own meals, and tired them out. The study did show that LEDs warmed with amber filters attracted fewer insects.

For fireflies in North America, though, amber had the opposite result. Scientists studied a species that’s common in the eastern U.S. and Canada. They exposed courting fireflies to different colors and intensities of light. And they found that amber light cut down on the “flashiness” of males and the response by females more than any other color.

And yet another study looked at fireflies in a forest in Brazil. It found that artificial lights were a bigger threat than habitat destruction or encroaching cities.

So for the insect kingdom, it seems, there’s no such thing as a good artificial nightlight.

Script by Damond Benningfield

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