It’s not certain why moths are attracted to lights, however, it is thought that the light confuses the moth’s navigational system.
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Come to the light
If you go out in the dead of night, you might be surprised to see a group of people gathered around a bright light in the middle of the dark. While this may appear like some kind of strange ritual, in fact, this may simply be a group of naturalists out to trap moths.
Moth traps function by having a bright light positioned above a box. The moths are drawn to the light and then are trapped within it. Luckily, the moths can be then captured unharmed, and released without injury, adding to our knowledge of the natural world.
Not all moths are attracted to light; however, there are many species of day-flying moths that do not come to the light, as well as some nighttime flying species. These species cannot be trapped in one of these fancy contraptions, and must instead be captured by other methods.
Why do moths go to the light?
The fact that moths go to the light is something that we are all aware of, and something most of us have observed. Yet, why this might occur, we aren’t so sure. It was once said that moths were attracted to the light, as they were attracted to the light of the moon. However, this theory would have no evolutionary advantage for the moths.
| Behavior | Explanation |
|---|---|
| Positive Phototaxis | Moths exhibit positive phototaxis, which means they are attracted to sources of light. |
| Circling Behavior | Moths often circle around lights, repeatedly approaching and flying away from the light source. |
| Resting near Lights | Some moths may rest near light sources, especially during the nighttime when lights are more visible. |
| Disruption of Navigation | Artificial lights can disrupt the moths’ natural navigation cues, causing them to become disoriented. |
| Aggregations | Moths may gather in large numbers around lights, creating swarms or congregations. |
| Vulnerability to Predators | Moths attracted to lights can become more vulnerable to predation by nocturnal predators. |
The most common theory today is that moths actually use the light of the moon to navigate by. As the moon is a great distance away, moths can keep the moon on the same side of them in order to head in a particular direction, and thereby navigate their way through the night, particularly on long migrations.
However, artificial lights are much closer, meaning that when the moths try to use them to navigate by they slowly spiral into the centre, until eventually, they meet the source of the light. This is not ideal for the moth, preventing them from being able to find food or a mate.
| Theory/Explanation | Description |
|---|---|
| Positive Phototaxis | Moths are naturally attracted to light sources, potentially due to their use of moonlight for navigation. |
| Misdirected Navigation | Moths mistake artificial lights for celestial objects, such as the moon or stars, and navigate towards them. |
| Disruption of Circadian Rhythms | Artificial lights can disrupt the moths’ circadian rhythms, affecting their normal behavioral patterns. |
| Heat and UV Attraction | Moths may be attracted to lights because they emit heat or ultraviolet (UV) radiation, which they perceive as cues. |
| Insect-Eating Predators | Moths may be drawn to lights due to the presence of insect-eating predators, such as bats, near light sources. |
| Cultural Adaptation | Moths may have adapted to natural light sources, but artificial lights can trigger their instinctive behaviors. |
Also read: Moths Reproduction Explained (Larvae, Eggs,…)
Escape route
Some scientists also argue that moths may head towards the light as an escape route from predators. If a moth were to be disturbed, heading up towards the light is more likely to get them out of harm’s way, than heading to the ground.
Sexy lamp
A final theory that has been voiced has been that male moths are mistaking artificial light for females. This is because it has been found that female pheromones, chemicals released to attract a mate, are slightly luminescent for the moths. This theory would mean that our light bulbs look like very big and sexy female moths to the males.
The moth snowstorm
The overuse of lighting within the human environment has had serious repercussions for moth populations. It is believed that moth declines can be partly linked to street lighting. Many moths end up exhausting themselves bashing into lights, resulting in their eventual death.
Moth predators have also learnt to take advantage of the moth’s habitats, with bats and owls known to hang around lights, picking off the moths that are drawn into the light.
Famously, the phrase ‘moth snowstorm’ has been used to describe the appearance of many hundreds and thousands of moths in car headlights in the past. Today you can drive a great distance without seeing hardly any moths. As well as light pollution, this demise of the moths can be linked to loss of habitat and use of pesticides.
Return of the moths
Some scientists and responsible organizations are trying to reverse the negative effects of light on moths. In some particularly experimental towns, red lighting is being used to replace the typical white lighting. White lighting, particularly newer, more energy-efficient LED lights, have been found to be highly attractive to moths, while red lighting does not have the same effect on them.
Other methods of reducing impact are through reducing the light shining upwards and outwards from lamps, by having them angled differently and positioned lower. Lights can also be turned off at hours when few people are likely to be outside, meaning that at least for some of the night nighttime creatures get to have a rest.
True or false
While the theory that moths use the moon to navigate by and therefore are attracted to artificial light may be the best we have so far, there are still those that do not believe it to be the right answer. After all, if moths required the moon to navigate, what do they do on a moonless night? The way that moths approach lights has also been argued to not be quite what would be expected if they had mistaken it for the moon.
Still, until someone provides a better explanation of this phenomenon, the phantom moon may be the best idea we have.
