Moths Guided by Lights

Have you ever sat down on a porch in the evening times with the porch lights on and notice the bugs flying in towards you? The moths in particular have a interesting attraction to light, whether its a candle or a bug zapper. But why is this? Why are moths so attracted to light even though it poses a huge risk to them? It seems like an evolutionary mistake for moths to have this sort of dangerous attraction.

In fact, it may actually be an unintended flaw in evolutionary history.

There definitely is a relationship between moths and light, and scientists call this relationship positively phototactic. This basically means that they are sensitive to light and tend to move towards light. Most of the theories involving a moth's attraction to light is dependent upon this relationship.

Most moths migrate and in order to fly around correctly, it is theorized that they use light reflected off the moon and sun to judge their up-down orientation. Based upon the intensity of light touching them, their brains could sense their position. Thus, when they go near a light source, they become very confused and don't really know where they are going. They don't expect to reach the light source, or fly above it. This causes them to fly around maniacally as they try to find their bearings.

However, there is so much light that comes from various sources, so I find this theory hard to believe. I feel as if the moth can adapt to these sort of changes fairly easily, and thus, this theory doesn't really seem to apply. It also seems as if the light is more disorienting to the moths rather than attracting, but if that were the case wouldn't they just fly straight into the fire?

They may also use light as an escape-mechanism. Normally, they would fly towards the sun or moon in the case that a predator comes and startles them. However, they would just fly towards a certain light-source to their perilous death.

This still seems a bit far-fetched because I feel as if moths normally aren't escaping from anything when they are attracted to the lights in my front porch. They usually just seem like they're flying around.

Another, more empathetic reason, is that moths are afraid of the dark. They take more time to adjust to the darkness after being exposed to light. For example, we are blinded slightly when we turn on a bright light after sitting in a dark room for a while. However, for moths this process takes much longer because their eyes focus light onto a single sensor called ommatidium. Therefore, they stay near the light in order to avoid the dark. In the case that they escape the light, their brains are too small to remember ever being in the light, and since they are still blinded, they usually end right back to where they started.

This seems to be a little more reasonable in the fact that it takes account the moth's ability to see and perceive light, and it is a little more logical that the moth wouldn't leave the light in fear of being eaten.

The relationship between moth and light is a curious one that shows that evolution can create a certain characteristic that may have been useful, but doesn't adapt quickly enough to human society. It may have been a necessary good, but now becomes an inevitable evil.

Perhaps it may even show our flaws in some figurative way. Maybe we lead ourselves to some sort of hope, only to realize much later on that this hope we're going towards is a burning candle.


Looking around online, I discovered another interesting alternate hypothesis that you did not mention. This hypothesis addresses the moth's attraction to candles, specifically. According to Philip Callahan, an entomologist that formerly worked with the U.S. Department of Agriculture, male moths are attracted to candles under the false belief that they are females sending out sex signals. I found this information in both this article: and this scientific abstract:

According to Callahan's work, the infrared light spectrum emitted by a candle flame happens to contain a few of the exact same frequencies of light given off by female moths' pheromones, or sex hormones. Callahan had previously discovered that the pheromones are luminescent, which means that they glow very faintly. Therefore, Callahan believes that male moths are attracted to candles because they mistake them for female moths. Sometimes, the male moth can die in an attempt to "mate" with the candle flame. I thought that this hypothesis was very interesting!

Wow! That is crazy. Imagine trying to get with a hot girl and then burning in ashes for it.

I think there could be numerous explanations for a moth's attraction to light, and they could even be combinations of these theories.

My only real question was why would evolution set something up that poses such a huge risk to the individual?

I feel as if society has evolved itself separate from nature, which makes certain features of animals, such as moth's attraction to light, become useless.

It's a little sad, but also very interesting.

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