Why Are Bugs Attracted to Light

Why Are Bugs Attracted to Light: The Different Explanations

Imagine sitting outside comfortably on a warm summer evening with your favorite book and a cup of tea. Flipping over the pages and sipping your drink and you suddenly spot loads of bugs hovering over the porch light! But wait, why are bugs attracted to light?

What is more interesting is that as the bugs move towards the light, it is a self-destructive venture. It might seem strange to you but buzzing around the light often causes their demise.

To make you understand it better, we will explain why this happens. We will also discuss phototaxis, which is the movement of bugs toward sources of artificial lights or even candles.

What Is Phototaxis?

If you are observant, then you probably have noticed the behavior of bugs around the light. Be it your porch light, street light, or even a flame, you will see dozens of them just moving around that source of light frantically.

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You can see this especially during the dark nights of the summer season. As mentioned, the real twist in the story, though, is that this light is harmful to them, and this can be explained by phototaxis.

To define phototaxis, we can simply say that it is any movement that organisms make in response to light. You can further categorize it into negative and positive phototaxis.

All positively phototactic organisms run towards sources of light; for example, moths and flies.  On the contrary, negatively phototactic organisms run away from sources of light, and they include cockroaches and earthworms.

Why Are Bugs Attracted to Light?

Many theories and research have been made to target this issue, but most of them are somewhat just presumptions. None of the scientists have been able to pinpoint one single explanation for this queer behavior. With that in mind, we will list down a few of them for you so that you can understand this strange phenomenon better.

1. Internal Navigation Systems

Bugs have internal navigation systems, and according to some entomologists, these unnatural sources of light hamper the insect’s navigation systems.

As part of evolution, these bugs have mostly evolved by using natural sources of light such as the stars and moon. Through positive phototaxis, these bugs used to move around by aligning themselves at a certain angle with respect to the light source. Such is a behavior called transverse orientation.

On that note, no matter how much the bugs move around, the angle remains the same for the most part since the moon is so far away. What happens when there are unnatural sources of light is that these bugs try to maintain their alignment. In an attempt to do so, you will find these bugs hovering around the light source in circles.

The circumstances are somewhat annoying for these poor bugs. It is so because around light sources that are artificial, the angle keeps changing. Thus, the alignment also has to be set repeatedly.

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2. Directions

Some scientists believe that bugs use lights as a source of direction. Instead of moving around in the dark, the bugs can use lights to guide them around.

A source of light basically serves to indicate that the path is clear. It also gives directions to the bugs to avoid any hindrances that they might encounter in the dark. Hence, to have a clear pathway to move around, these bugs might be attracted to light sources.

3. UV Light

Scientists believe that flowers reflect UV light. At the same time, some sources of light might also emit varying amounts of UV light. What happens is that these bugs have mistaken the light as a source for food!

As a result, you see these poor bugs moving around a porch light or street light in search of food just because the bugs can sense UV light.

4. Female Moths or Light Source?

An entomologist named Philip Callahan put forward the theory that male moths mistake light sources for female moths. He proposed that the pheromones give off infrared light that has similar frequencies like the light given off from unnatural light sources. So, male moths make a self-destructive nosedive into the light source while attempting to mate all this time.

Here is something to note, though. Previously, this scientist also discovered that this light given off by female moths is weakly luminescent, so all-in-all, this idea might seem flawed.

Another loophole in this theory is that bugs are more attracted to UV light as compared to infrared, as mentioned above. As such, it seems kind of odd that they would even consider moving towards infrared.

That too, for mating purposes when they are not even attracted to that frequency? Truly sounds like a bizarre idea.

5. Full Moon vs. New Moon

Another observation made by scientists is that these bugs tend to be attracted to lights more during the new moon week. On the contrary, during the week of the full moon, bugs are attracted less to unnatural light sources.

This observation gave rise to a new theory that the bugs are moving toward the moon. However, it soon became vague because if the bugs kept moving towards the moon, then how would they be able to carry out their life cycles?


There are many observations made and theories put forward to explain as to why are bugs attracted to light. However, as described above, it can be concluded that most of the theories are not only confusing but also absurd. Most of them have loopholes or are contradictory to the other facts stated by science.

Nonetheless, we can still, to a certain extent, take into account that maybe bugs use light sources for guiding them. Just so these bugs can move around freely and without any obstacle in their ways.

Since this issue proves to be very tough to address scientifically, there is no definite answer to it. We truly still have to do a lot of research in order to conclude. As for now, just wait for the bugs to go away as they wish, while you sip your tea and read your book.

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