According to expert opinion, insects are attracted to light for the purpose of self-preservation. Insects are attracted to light because their search for food and mates is dependent on light. For example, some moths that thrive on cotton use moonlight to direct them to cotton farms. These moths are equipped with tiny antennae. The shadow of the tips of these antennae must fall on certain spots in their eyes – and if it does not, then the moths suitably alter the direction of their travel to bring the shadow back on those spots in the eyes. As a result, they do not lose their way even in the night. Moths that survive on the leaves of tobacco plants also find their way by moonlight just like the moths that eat the leaves of cotton plants.
Now that we have electric lights, certain moths might mistake the light of a bulb for the actual moon. Even a candle could be mistaken for the Moon. Having come in close proximity to such a source of light and to keep the tiny dots of shadow centered on its eyes, the moth keeps on flying around the light. Only then the shadow can be kept constantly centered on those spots in the eyes. However, when flying around in circles, some moths collide with the electric bulb. If the bulb is too hot, or if the source of light happens to be a candle instead of an electric bulb, then the moths instantly burn to death.
Many have heard of the simile ‘like a moth to a flame’ to signify strong attraction or preference. The underlying reason for this behavior could be lust, greed, thrill, or just something popular that’s just come out on the market. This is when we look at the simile and apply it to human beings.
When it comes to moths, though, there are a few other theories about why they seem intent on committing suicide by flying into candles, lamps, and other sources of artificial light. The explanation above focuses on the evolutionary aspect; moths were only introduced to electric lights about a century and a half ago. Hence, they evolved their navigation systems when the main sources of light on this planet were the sun, the stars, and the moon. The habit of flying at an angle to a far-off light source is known as transverse orientation. However, the weakness of this theory comes in when we think about fire as an additional light source.
It’s true that electric lights haven’t been around forever, but burning torches, campfires, and other forms of fire have been used as light sources for thousands of years. Natural selection should have killed off the kind of moths who get confused about whether the light source they’re circling is the moon or not.
There’s also some evidence that transfer navigation might not even be a system used by moths. It’s more of an intuition in migratory species. Since most moths don’t migrate, there’s no reason why they need to depend on moonlight for navigation purposes.
Another explanation came from Philip Callahan, who was an entomologist in the U.S. Department of Agriculture during the 1970s. Callahan noticed that candle flames gave off a certain infrared light spectrum that contained some of the light frequencies that were also given off by the pheromones or sex hormones of female moths. Pheromones are also slightly luminescent, so the glow from any light source might be mistaken for them. This means that male moths circle a flame or light bulb believing that they are in the presence of a female.
Again, though, this theory has certain holes and weaknesses. For instance, ultraviolet light is more attractive to moths and other insects than infrared light. UV light doesn’t have the same wavelengths as the glowing pheromones of moths, so the explanation doesn’t seem to hold.
Yet another theory is that the moths are actually flying to the dark space behind the light source, which is probably the safest hiding place in their reasoning. Another idea states that the light blinds the moths and makes them lose their orientation.
The holes in the theories about why moths are attracted towards light also have certain explanations. Any one or more of these ideas could be the final answer; however, here’s still room for research and studies in order to best answer this question.
- How do insects like mosquitoes and bees infect us through their sting or bite?
- How does cockroach easily avoid a swipe? Which organ forewarns it about the attack?
- Why do ants touch each other with their heads when they meet? Why do they walk in a file one behind another?
- Why does tail of a house-lizard (gecko) jerk and toss about for some time even after cutting off from the body?