Why Are Bugs Attracted to Light?

Why Are Bugs Attracted to Light?

The truth is that scientists do not know exactly why certain kinds of bugs are so entranced by light that they will regularly fly to their doom just to get closer. There are a few working theories, but at this point, it’s unfortunately impossible to say for certain. 

Unfortunately, science has also yet to get to a point where we can just ask the bugs why they do what they do. It’s all for the best, though. Chances are that their answers wouldn’t be particularly articulate.

We will explore a few of the most prominent scientific theories as to why insects can’t resist lights, but first, we have to establish some key terms.

What Is Phototaxis?

Phototaxis is an organism or creature’s directional reaction to light. For instance, plants or insects like moths move toward sources of light. On the other hand, insects like cockroaches reflexively move away from any and all light. That’s why when you flick on the kitchen lights to get a midnight snack, cockroaches scatter — and both yours and their night is ruined. 

There are two terms that help explain this phenomenon in more depth and how it can relate to various species: positive phototaxis and negative phototaxis.

Positive Phototaxis

Going back to the moth example, we have all seen when these and other insects seem to immediately fly to a nearby light. There is a reason the saying “like a moth to a flame” is so popular, after all. This is an example of positive phototaxis, in which the moths react to light by getting closer to it.

Negative Phototaxis

Opposite to positive phototaxis, we, of course, have negative phototaxis. Cockroaches are an example of the idea of negative phototaxis. The moment a light is turned on, their immediate reaction is to run away and hide. This is likely due to the fact that cockroaches are nocturnal, as well as being shy and nonaggressive.

Not only do they not want to be near light because their internal clock tells them to be awake at night, but also because they are visible to predators in the light.

Bugs Might Mistake Artificial Lights for the Moon or Sun

The first theory explaining why bugs search out artificial light is the most popular, but it still hasn’t been proven for certain. Many scientists believe that bugs could view something as innocuous as a porch light and mistake it for the moon.

If an insect uses the moon or the sun to navigate, its internal compass will be fundamentally thrown off when they see another light source. Since this light source is so much closer than the moon, it is often easier for them to see. They then stay because it either becomes too difficult for their eyes to adjust again to the darkness, or they just don’t think about it too hard.

They Could See Lights as an Escape Route

Another working hypothesis as to why insects act how they do is that lights are one of their best means of escaping a predator. If they were hiding in a plant, bush, or tree, they need to keep a celestial body like the moon or sun in their sights to know how to escape.

When a predator approaches, they can then take off in the direction of the moon or sun to try to get away and save their lives. If they confuse a light for a lunar or solar body, they will fly in that direction instead.

Ultraviolet Light Might Look Similar to Flowers

When we think of bugs attracted to light, many of us will think of moths first and foremost. Certain kinds of moths feed on plant nectar, so they are regularly searching out flowers for them to feed on. They often find these flowers through the ultraviolet light that they give off.

If you have an ultraviolet lamp or even a regular lamp that gives off just a bit of ultraviolet light, a moth might think they have hit the motherload. After that, they will fly toward it, thinking that they’re in for a flower buffet.

Are Bugs More Attracted to Certain Types of Light Than Others?

You might have noticed that if there are a few different kinds of lights outside, one light might have significantly more bugs around it than others.

In all likelihood, this is because the bugs have an easier time seeing certain kinds of life as opposed to others. Here are the lights that bugs can’t get enough of, as well as the ones you can use to keep them at arm’s length.

White Light

White and whitish blue light are among the most well-loved for bugs. If a moth were to ever decorate its home, it would certainly choose this kind of light for each and every room. The moth would also never turn any of the lights off. We are confident that the electric bill for this moth-house would be absurd.

While a “moth-house” might sound like a fun idea for a book you can read to your kids to get them to fall asleep at night, the last thing you want is for your home to turn into one. If you are worried about white porch lights attracting moths and other insects, you can turn it off, use a natural bug repellent like essential oils, or try a light of a different color.

Red and Yellow Light

As opposed to white light, red and yellow light are not as enticing for bugs like moths. Although it can’t be said for certain, it is reasonable to assume that the reason these kinds of bugs are the most attracted to white light is that it’s the most similar to the glow given off by the moon.

Meanwhile, red lights, yellow lights, and other colors on a similar spectrum are less likely to look like the moon. Not only that, but red, yellow, and orange are among the colors that bugs have the most trouble seeing.

Swapping out your porch light for bulbs of a different color might not get rid of all the bugs swarming around your space, but it is likely to make a dent in them. Moths will probably be less attracted to this light source, but different species of bugs might remain undeterred.

Ultraviolet Light

As we mentioned before, if bugs are attracted to white light, they are infatuated with ultraviolet light. Like the true reason that insects flock to light in the first place, we do not know exactly why this is.

Some scientists speculate that flower petals give off ultraviolet light to attract pollinating species (and save water). So, if a bug sees ultraviolet light, it might mistake it for a welcoming flower. 

If a lamp gives off even a small amount of ultraviolet light, that would be enough to get a plethora of moths in a frenzy. Why do they stay near or even in the light after realizing it isn’t a flower? The answer to that is a simple one, at least – moths just don’t get it.

Which Bugs Are Attracted to Light?

While moths are likely the most famous bugs attracted to light, they are far from the only ones. Flies, mayflies, water bugs, spiders, beetles, and mosquitoes can all be attracted to light too.

How To Care for a Bug Bite

If you or your kids find yourselves with an itchy bug bite in need of care, we have an all-natural solution for you. Simply place a MagicPatch Itch Relief Patch over the bite, and let it do its work.

The clever Grid-Relief Technology within each patch creates a microlift in the skin, allowing the lymphatic system to drain more effectively and for itchiness to cease. After you’ve been itching that mosquito bite for days, this patch is the light at the end of the tunnel. 


Phototaxis | Carnegie Science

The secret ultraviolet colours of sunflowers attract pollinators and preserve water | The Conversation

Yellow Light Bulbs Keep Bugs Away | The Spruce

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