Moths and Light

Back at the very beginning of things, the Creator of All worked for a long time making the plants and animals. It was hard work! Creator was tired! But the job wasn't finished yet, because every kind of animal came to learn where they should live, and what they should eat.

“You monkeys are good climbers. You can live in the trees eating fruits and nuts,” said Creator. “You big cattle, deer, elk, sheep: you need plenty of food. You can live on the plains and eat grass. You fish,” Creator sighed, “you can live in the water and eat anything that fits your mouth,” and so forth. (When you tell this story, insert other animals and habitats as you wish.) There were so many animals!

Then the moths and butterflies came. “What shall we eat?” they asked. Creator patiently replied, “I have assigned different plants for your young ones to eat. You must be careful to lay your eggs there, so the caterpillars will have the correct food. But when you become winged adults, I want you to drink the nectar of flowers. Any kind you like, I have created so many! Help yourselves!”

But instead of being grateful, the butterflies looked jealously at the moths. “Can't you divide up the flowers so that we get our share, and don't have to dodge those fat fuzzy moths when we're drinking?”

Creator frowned at the selfish butterflies, and had an idea. “I have made some of the flowers bloom only in the daytime, some only at night. So I can assign one group of you to feed during the day, and the others to drink at night. What do you think of that?”

The butterflies were delighted. “Of course we'll get daylight! That way everyone can admire our beautifully colored wings and slim bodies as we flit among the flowers in the sunshine. Let those dull-winged moths fly at night. Who cares about colors when there's just moonlight and starlight?”

The moths tried to object. “We like light too! We need to be able to find our flowers!”

Creator was tired and just wanted to resolve this. “Moths, I will give you very sensitive eyes, so that you can use Moonlight for direction. You will be able to see even when there's only starlight, and I will give many of your night-blooming flowers white petals, so that they're easy to find even in dim light. I will make them deep-throated, and give you very long tongues (proboscis) so that only you can drink from them. And I will give them beautiful perfumes, that you can sense with your feathery antennae, so that you can find them even in darkness!”

The moths thought it over. Sensitive eyes? Special deep, perfumed flowers only for them? They decided to let the gaudy butterflies have the day shift. Moths would rule the night!

And so it has been, for the most part. There are some moths who feed on colorful flowers during the day (Sphinx moths hover at my zinnias) but most of them fly at night. And they still love light, even if they hardly require it to find their flowers.


Moths are not the only night-flying insects affected by light. Ants, flies, mayflies, even migrating hoards of grasshoppers are attracted to ALAN (artificial light at night). They can circle around our street lamps until they die of exhaustion – or are gobbled by bats or other nocturnal predators. The glint of city lights on wet streets confuses mayflies into laying their eggs on the pavement, instead of in river water. Fireflies can't signal for mates when their own cold light is swamped by our electrical variety.

LED streetlights are favored by cities because they use far less power than incandescent or sodium vapor lamps, but their bluish light seems more attractive to insects. Perhaps they mimic the cool Moon and star light which many night-fliers use for orientation. On a Moonless night, artificial sky glow in 20% of Earth's cities is brighter than the stars!

Researchers in Hungary, Brazil, Netherlands as well as many U.S. sites, blame artificial lights for part of the “insect apocalypse” as worldwide numbers of insects fall by as much as 80%. What's a bug to do?

Because of insects' importance as pollinators, recyclers, and members of the food chain, cities and national parks are experimenting with ways to lessen the insect impact of our ALAN while keeping the human benefits.

Color and location are important. In Hungary, mayflies stay safe when bridges' bluish lights are mounted low near the water, while the street lights are dim and yellowish. Grand Teton National Park finds that dim reddish streetlights attract fewer insects – and let visitors see the stars. For our own outdoor lighting, we can seek yellow “bug lights,” which are now available in compact fluorescent and LED form.

Night-flying moths, flies, mayflies, ants, and grasshoppers are well adapted to low levels of cool light. Let's leave them to it!



Story sources:

To my surprise, I couldn't find any folktales explaining why moths are attracted to light. I made up this story borrowing the image of a tired Creator from a Japanese folktale (which doesn't mention butterflies or moths). The notion of rivalry between the two kinds of Lepidoptera was inspired by “Cynthia the Caterpillar,” an original story by Judith Black

Fact sources:

"Fatal attraction to light at night pummels insects:" Elizabeth Pennisi. SCIENCE magazine May 7, 2021 (Vol 372 No 6542), pp 556-7.