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 favourite book and tea. Flipping over the pages and sipping your drink, 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, 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 behaviour 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.

You can see this, especially during the 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 say that it is any movement 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 light sources, including cockroaches and earthworms.

Why Are Bugs Attracted to Light?

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

1. Internal Navigation Systems

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

As part of evolution, these bugs have evolved mainly using natural light sources such as the stars and moon. Through positive phototaxis, these bugs moved around by aligning themselves at a certain angle concerning the light source. Such is a behaviour called transverse orientation.

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. 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.

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

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

3. UV Light

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

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 proposed the theory that male moths mistake light sources for female moths. He proposed that the pheromones give off infrared light with similar frequencies to the light 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 this idea might seem flawed.

Another loophole in this theory is that bugs are more attracted to UV light than infrared. It seems odd that they would even consider moving towards infrared.

That, too, for mating purposes when they are not even attracted to that frequency? It honestly 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?


Many observations have been made, and theories explain why bugs are 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 to guide 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. We honestly still have to do a lot of research to conclude. As for now, please wait for the bugs to go away as they wish while you sip your tea and read your book.

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