Why Are Moths Attracted to Light? Here Is the Science Behind It All

Moth at the table

We've all heard the expression before; the one that goes, 'like a moth to the flame.' But why are moths attracted to light in the first place? If you live somewhere with a high insect population, you'll know that it's not just moths, either.

In order to answer this 'why are moths attracted to light' question, it helps to know how they and other insects like them perceive the natural world.

Why Are Moths Attracted to Light?

Moths are part of a category of beings that are classified as phototactic. This means how they relate to light affects how and where they move. Insects that are positively phototactic actively seek out light.

Moths are an example of this. Other insects, like cockroaches or earthworms, are negatively phototactic, which means that they actively avoid light. Scientists have no way of knowing for certain what causes these drives, but there are some interesting theories that may explain the answer.

These theories have to do with a given insect's abilities and instincts. It could be what they must do to navigate their surroundings with the meager eyesight evolution has afforded them.

It could also be related to how they've interacted with light so that they can survive and not be eaten by larger predators. There are even more far flung theories. Some believe that because of a moth's particular kind of eyesight, it can see the light wavelengths of the nectar it eats.

According to this theory, it confuses a bright light with an abundant food source. There's even the theory that the moths believe a fire's light is a female moth, which they fatally try to mate with.

Through the Eyes of a Moth

So how do moths see the world? And what would cause them to be so attracted to something so simple? Why are moths attracted to light, no matter what kind it is?

It helps to understand that the eyes of all nocturnal beings are fundamentally different than the eyes of creatures who live by day.

In the case of the moth, the light source they're usually reacting to is the light of the moon. Moths don't actually like to fly in no light whatsoever.

Drawn to the Next Meal


One of the most simple ways to think about it is this: if there's a large water source nearby, it reflects the light of the moon most of the time the moon is out. The presence of a water source probably means that there is an adequate amount of plant life nearby for a moth to feed on.

Moths may sip on flower and plant nectar, eat rotting fruit or dung, or eat tree sap and other pollen. So it could be that the moths present at your campfire think that they're about to embark upon a feast.

Glowing Nectar


Moths love the light

Image by A_Werdan from Pixabay

But what if being able to explain 'why are moths attracted to light?' involves the food source itself? There is another theory that moths can actually see the level of light in a plant via the ability to read how much light the plant is emitting on the UV spectrum.

Why might this be the case? We already know that moths can detect if a plant is giving off high levels of CO2, which may indicate the presence of more nectar.

The Thrill of the Chase


And what gives credence to the theory that moths mistake light for the chance to mate? Well for this we have Philip Callahan to thank. He worked for the U.S. Department of Agriculture in the 1970s and discovered something about how both candles and female moths radiate.

Apparently, he learned, lit candles emit an infrared light spectrum that is highly similar to the pheromone that female moths emit. In this way, it would appear that the moth is actively trying to 'mate' with an open flame. This scenario of course ultimately causes the moth in question to die.

The Most Likely Explanation

The previous mating theory, as plausible as it may be, does not explain why moths are even more attracted to brighter or 'whiter' lights. Which brings us to the most likely answer to 'why are moths attracted to light?'

Light, the Moth's True North


Before the invention of the compass, sailors used celestial bodies and the rising or setting sun to help them orient their vessels. Utilizing the north star, or 'Polaris' allowed sailors to orient themselves at night because of the star's position in the sky.

It's been suggested that moths use the moon as a similar 'north star.' The moon is a much brighter light source. However, since the moth's eyesight is so rudimentary, it may focus on an even brighter immediate light source like a lamp or a fire.

For a Moon Compass


Moths and moon light

Image by Florian Kurz from Pixabay

The moon itself is the closest celestial body we can see in the night sky. This could be especially useful to the moth and could answer the question 'why are moths attracted to light?'

This theory suggests that moths move via 'transverse orientation.' This means that a moth might maintain a fixed angle with the light of the moon so that they can fly in a straight line. 

In this case, a different or artificial light may be brighter than the moon, but to the moth it could be mistaken for the moon since they're programmed to fly in reaction to the brightest light.

Surface Moons


Moon light surface moths

Image by PIRO4D from Pixabay

Because of an alternate light's position on the surface of the earth, the moth may be surprised to find that they've reached their navigation beacon; something unusual to them. Whatever causes this drive, though, overcomes the other drives the moths may have to do other things, which is why you see moths landing on camping lanterns or flying into bug zappers. This theory though, would probably only apply to migratory moths, as smaller moths have no reason to travel great distances.

How Humans Relate to the Plight of the Moth

Moth on the screen

Image by John Cassano from Pixabay

No matter how you answer the question why are moths attracted to light, the way people have been mystified by the sight of the moth's attraction to light is in itself worth thinking about. The image of a moth flying into a flame is now part of the collective human consciousness. 

"Judge the moth by the beauty of the candle." - Rumi

Several stories have been written in an homage to the occurrence as well as a great deal of poetry. We'll feature a couple of these examples here so you have a more holistic understanding of moths and flames.

Virginia Woolf's Take


This rumination on moths and death takes the form of a short essay called 'The Death of the Moth.' It's a quick read, only a few pages, and is Woolf's attempt to play out the struggles of day-to-day life across the seasons.

"Moths are just butterflies with their makeup taken off." - Anon

She stresses that human beings are very similar to the moth, especially in how we relate to death. She further illustrates that, no matter how hard humans struggle to stay alive, death is an inevitable force that will come for everyone eventually.

Watching a moth struggle and then ultimately die on her window sill eventually brings her ideas full circle.

Annie Dillard's Take


A far more dramatic tale involving fire, Annie Dillard's 'The Death of a Moth,' is a piece that challenges death's finality, even if the challenge is brief. She writes from her own perspective.

Moth: "I gave you my life."

Flame: "I allowed you to kiss me."

- Hazrat Inayat Khan

At this point in her life, she's living alone and has a fascination with the simple elements of the natural world. After describing seeing disembodied moth wings in strange places, she paints a scene of her own, while reading by candlelight one night.

She describes a female moth's death by a candle's flame in striking detail. This includes the fast burn of the wings and the slow burn of the main body.

She ends up coming away from the experience with a newfound respect for the moth itself. She relates the moth's death to the death of other things in the human experience. The beautiful way the moth glows even in its own destruction might suggest beauty in the pain of loss people experience.

The moth glows brightly and beautifully, even though its own action caused it to die. In this same way, the endings and little deaths that can happen, though painful, could be beautiful in how they cause people to grow.

Conclusion

Moth on the wooden flatform

Image by Andreas Lischka from Pixabay

So what kind of light are you attracted to in your life?

And how does knowing some of the reasons that moths might be attracted to light change how you look at these winged creatures?

We hope you've come away from away from this investigation understanding both the scientific mechanisms that may be at play and how humans relate to these phenomena emotionally.

Be sure to continue to research on your own if you're still curious, or take a look at the many short stories related to moths if you'd like to take a deeper exploration.

And the next time you experience 'being a moth to a flame' you'll know what's happening.

Featured Image: Image by Jordan Davis from Pixabay

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