The past couple of weeks have brought a barrage of memes about moths and their legendary love affair with lamps. If you’ve missed out on it, ask a Cool Teen or an internet-obsessed adult in your life, and they’ll fill you in. Now that we’re all on the same page, we all know that these memes riff on the idea that moths are attracted to light sources, even to the point that they’ll fly into a candle or other fire, “Like a moth to the flame,” as the old saying goes. But why the heck do they do this?
The answer is as elusive as it is fascinating.
Before we dig into moth psychology, though, let’s briefly discuss why this meme is trending. On July 14, redditor No_Reason27 posted a close-up photo of a moth outside their window on the r/creepy subreddit. It has received 33 thousand upvotes since then, and the top comment says, “Hey buddy you have any LAMPS?!” On August 6, Twitter user jonwadec posted the image along with the caption “y’all got any fuckin lamps?” Based on the moth’s surreal and grotesque appearance, the tweet and the original Reddit comment suggest that the moth is begging for a lamp, compelled to pursue it by addiction, desire, or some mix of both. The tweet went viral with over 230 thousand likes and 80 thousand retweets.
Since then, the meme has continued to build, spawning countless iterations as of this article’s publication (including one by this reporter), spanning from formulaic takes on the distracted boyfriend meme to some serious levels of internet brain-poisoning.
At the risk of over-generalizing, literally every single person in the world has seen a moth fluttering around a street light or porch light, or they’ve seen moths fly in the front door in the summer time. These experiences make it clear that something is going on between moths and lamps, and this is where we come to the first hypothesis about what drives moths to the flame.
They Use the Moon to Navigate
One of the longest-standing hypotheses about why moths seek out artificial sources of light is that they have evolved to use natural lights for navigation. The idea is that by maintaining a trajectory with a constant angle in relation to the moon, a moth can ensure it is continuing on a forward path. As the moth flies, the moon stays mostly stationary, providing a fixed reference point for navigation. This behavior is called transverse orientation.
“Moths often use the moon to orient themselves during night flight,” Mike Saunders, Ph.D., a professor of entomology at Penn State, said in 2008. “Using the moon as a reference, moths can sustain linear flight in a given direction.” With the advent of lamps, though, moths got all messed up. For instance, if a moth mistakes a porch light for the moon and tries to maintain a fixed distance from it, the confused insect could just end up circling the lamp until it’s too tired to fly. Contrary to what the memes suggest, this phenomenon is less about desire and more about confusion.
It sounds like a tidy explanation, but other researchers have questioned the validity of this hypothesis. After all, humans have built fires for at least a million years (up to 1.5 million years, by some archaeologists’ estimates), and moths still aren’t extinct. If they were flying into the nearest light source all the time, everything we know about evolution tells us that this behavior would not persist to the present day. That brings us to the next hypothesis.
Moths Actually Want to Have Sex With Lamps
It sounds bizarre, but this hypothesis had some scientific support. In 1977, USDA entomologist Philip Callahan published a paper in the journal Applied Optics suggesting that moths may confuse the infrared radiation coming from flames and electric lights for sex pheromones. In the paper, Callahan wrote that the sex pheromone, acetate, released by the female cabbage looper moth (Trichoplusia ni) bears the same spectral emission pattern as the infrared radiation given off by a candle. In other words, for a moth that can detect light in the infrared spectrum, a candle’s heat might look like a female moth that wants to mate.
“The male moth is highly attracted to and dies attempting to mate with the candle flame,” he wrote.
It’s not clear whether the male moth is actually attracted to the light qualities of the female’s sex pheromones, though, so this hypothesis stands without strong proof. It’s possible that another portion of the light spectrum may explain moths’ compulsion to fly into lamps, though.
Ultraviolet Light Makes Moths Mistake Lamps For Food
It may not be infrared light so much as ultraviolet light that confuses moths into seeking out lamps. Moths, much like bees, have been shown to use visual cues to identify the flowers they feed on, and a big part of this is ultraviolet markings on the flowers. These markings, just outside the range of colors that we can see, tell moths where to find nectar.
It’s possible that if lamps give off light in the ultraviolet range, they’ll attract moths who are looking for a meal. Anyone who’s watched a bug zapper in action knows that it attracts moths like nobody’s business. Bug zappers emit ultraviolet light, making it a heck of a tricky lamp for moths. But these lights aren’t alone. Incandescent bulbs also give off a small amount of UV light, which lends support to this hypothesis.
Unfortunately, we don’t know for sure which — if any — of these hypotheses is correct. It’s also entirely possible that all of them, or at least elements of each explanation, are accurate, perhaps differing by moth species. One thing’s for sure, though: No matter why moths are attracted to lights, they sure make good comedic fodder.