Why flying insects gather at artificial light

One fun thing to do with a swarm of bug near a light is to take out your keys and shake them.

Keys will often ring in the ultrasonic and poorly mimic the frequencies that a lot of bats use.

If you have a population of bats that hunt near you, the bugs will typically just drop. Like, just drop to the ground as fast as they can.

They know the sound of hunting bats and your keys may be just close enough to that sound that they think they're being hunted. So they do the best that they can to get out of the way and go with gravity. At least, that's my theory.

Fun little thing to do as a bet or with the kiddos.

Interesting, I heard a story once that you can catch bats with keys: Put a bunch of keys in a sock and throw that in the air. If there is a bat near enough it might dive for and grab the object, then it gets drawn to the ground because the keys are too heavy. There you can catch it if you are quick.

Might be an urban myth, though it seems like it might just work.

Seems like a great way to get rabies.

Or a new strain of COVID...

or superpowers

Wrong, Batman had no superpowers. He was just good at martial arts, and had access to some nice equipment (because he was a billionaire).

So the costume was basically just a kink?

Yep. There was one early Batman series which revealed that his father had once dressed as a bat-man for a costume party. Batman wore the costume when apprehending a criminal who had done something awful to Batdad and the criminal, seeing the costume thought it was Batdad returned to life and panicked falling to his death.¹

⸻

1. Likely inaccurate description of the plot based on 45-year-old memories of reading the story in a library collection.

The underwear worn outside of the pants are a dead giveaway.

He had superhuman thirst for justice

Justice playing a metaphor for little flying insects in this case, upon which Batman places his hyperfocus. It makes sense.

Note that depending on your area this might be illegal. In France for example, bats are a protected species and it’s forbidden to kill or capture them.

Also depending on your area, there's a chance the bat may scratch you without you realizing it, and a few months or years later, you suddenly go mad and die in agony.

At least I'm more scared of rabies than any government fine. By the time you know something is wrong, you're already a corpse that's about to remember to stop moving.

Rabies can lay that dormant? And there’s no test?

Apparently, yes, and while there are tests, it's probably too late once symptoms have appeared:

Rabies virus travels through the nerves to the spinal cord and brain. This process can last approximately 3 to 12 weeks. The animal has no signs of illness during this time.[^1]

Several tests are necessary to diagnose rabies ante-mortem (before death) in humans; no single test is sufficient. Tests are performed on samples of saliva, serum, spinal fluid, and skin biopsies of hair follicles at the nape of the neck.[^2]

Once clinical signs of rabies appear, the disease is nearly always fatal, and treatment is typically supportive. Less than 20 cases of human survival from clinical rabies have been documented.[^3]

[^1]: https://www.cdc.gov/rabies/transmission/body.html

[^2]: https://www.cdc.gov/rabies/diagnosis/animals-humans.html

[^3]: https://www.cdc.gov/rabies/symptoms/index.html

Who in the world would know anything about it if you're out at night catching bats with a sock?

If you know that it’s a protected species you might want not to do that, even if there’s no one to see you.

Camping in Lassen area of Northern California as a kid, I would tease the bats by throwing a ball of tinfoil in the air. The bats would chase it.

more of a rural myth, I guess ;D

Well you have no sources and you can be full of it. But following the scientific method, I’ll try your hypothesis next chance I have! :D

If this turns out to not be true, and just said for the amusement of thinking of all the people jiggling their keys at insects, it reminds me of something a friend in high-school said to me:

"If you peel a banana, take a bite off the top, and then poke your index finger in to the middle of it, it will split in to perfect thirds".

Upon trying this, I discovered it was not true, and my friend just wanted to see me stick my finger in a banana...

I never tried (yet) but a quick search reveals a lot of people filming the "banana split in thirds" action, e.g. https://youtu.be/NoGXTXsamt4?si=ANNTdtcu1trOdQXP

It's still technically possible it's a hoax but, boy, that's a lot of effort to provide fake content to support the hoax.

?t=40s

Nice. Maybe GP got the wrong end, or it is a test of ripeness, or perhaps 'bite off the end' ruined it (it at least didn't seem to be necessary in the linked video).

Actually, I do this when making a banana split. Cut a piece off the top and then slowly press the banana into thirds. Then, lower the banana, with the bottom part of the banana still intact, into a tall glass. Smoother with cream, ice cream and/or syrup. Makes for a solid banana split.

funnily my friend just discovered that you can split it into thirds a few day ago and now does it whenever he eats a banana

A banana does actually third itself when split.

I'm still going to shake my keys at the next swarm I passby.

"If you hand is larger than your face . . . "

Ha, no way!

All this time I thought this was him being silly!

(For the record, the banana did NOT split nicely)

Too bad it's winter and I'll probably forget this before I have a chance to!

some moths have countermeasures

John said, “Listen, you can hear the jammer.” The what? “The jammer,” he said, “Watch the moths.” It turns out the moths, through evolution, had developed their own electronic countermeasures to jam the bat radar.

https://steveblank.com/2009/03/23/if-i-told-you-i%e2%80%99d-...

fascinating! There's also a wikipedia entry: https://en.wikipedia.org/wiki/Echolocation_jamming?useskin=v...

I need to buy an ultrasonic whistle and experiment with this! :)

Have you ever done that?

This is also hilarious too: https://www.reddit.com/r/nextfuckinglevel/comments/17jw3gm/d...

Apparently bees also drop when you turn the light off:

https://youtube.com/watch?v=OmG0OT6MWC8

What about the color? I know it is slightly orthogonal, but the article says: "This is true even at night, especially at short wavelengths (<450 nm)".

I always wondered: isn't there a light color that we human see and that minimizes the impact on the insects? Say if we only used red light in the cities, would it help?

Try different colors at your home!

Well I was hoping for something more scientific. I read a bit about that, and it seems like insects are more affected by smaller wavelengths (UV/blue rather than yellow/red) and some species polarized light.

But then if we know it, why don't we engineer the street lights to not attract insects?

Well I was hoping for something more scientific.

What is more scientific than testing the hypothesis yourself? That's science; that's its essential joy and spirit and nature.

    Have you reckon'd a thousand acres much? have you reckon'd the earth much?
    Have you practis'd so long to learn to read?
    Have you felt so proud to get at the meaning of poems?

    Stop this day and night with me and you shall possess the origin of all poems,
    You shall possess the good of the earth and sun, (there are millions of suns left,)
    You shall no longer take things at second or third hand, nor look through the eyes of the dead,
       nor feed on the spectres in books,
    You shall not look through my eyes either, nor take things from me,
    You shall listen to all sides and filter them from your self.

Someone else doing it is just reading.

What is more scientific than testing the hypothesis yourself?

Professionals doing it? Who know how to do it properly better than laymen?

With respect, that is the complete opposite of science! The only difference, the only barrier, between you and a 'scientist' is that someone else took that step to do it themselves. Tomorrow you could be a scientist - next time you have an idea!

You don't have to publish in Nature to be a scientist. Really, I mean that in the best way. I am a scientist every day. It's powerful, it's joyful, it's curious and exploratory (very important parts of your brain to work out, per research by professional scientists), it's extraordinarily practical: Science, by me, has reduced my energy consumption and bill by around (very roughly) 70%.

You're likely describing citizen science and engineering, which cannot really be considered for publication in Nature.

The work here represents many thousands if not millions of hours of accumulated scientific skill in building experiments that are likely to produce useful conclusions, rather than falsely rejecting the null hypothesis.

I've worked in citizen science and I have even done some exciting stuff in my garage, which attracted the world's leading researcher in my area of interest. The first thing I'd need to do with my tech is to bring it to his lab and reproduce it on science-grade equipment. then we would need to come up with good hypotheses we could test, and spend an enormous amount of time designing protocols, and debugging lab details. All of that comes before even thinking about writing a manuscript that would be accepted in nature, which is one of the most prestigious journals with enormous readership.

I don't want to discourage young folks who want to get into science, but the reality is that the vast majority of real science is dull work, such as requesting money, writing presentations to convince people you're right, and debugging experiments. I'm not defending this as the way it should be, but observing the reality of the situation. I have actually met a very small number of people who managed to turn citizen science into Big Science and get published, but they are a much smaller group than the folks who do bad citizen science in their garages and get attention on sites like Hackaday.

You're likely describing citizen science and engineering

That's what you are describing. If you read my comments, I am not talking about that (though I don't object to it), and my main point is that science is not defined by the type of work that gets published in journals, or by whatever qualifies as 'citizen science'.

I read all your comments carefully, in detail, before responding. Can you give us some examples of what you mean? I'm struggling to see how somebody on their own could come up with a non-trivial scientific result that was meaningful in any way.

a non-trivial scientific result that was meaningful in any way

I assume you mean non-trivial and meaningful to society and to the progress of human knowledge. My whole point is that those properties are not necessary to doing 'science'.

What I do is non-trivial and meaningful to me and sometimes to people I know, to a few people on the Internet, and/or to my community or co-workers. Though sometimes the data is trivial even to me, and still it's a joy, the joy of exploration and curiosity. Also, there are infinite questions beneath the threshold of professional science costs that can be investigated (and some of those are just hyper-local questions).

Science doesn't have to be big and globally meaningful. That stuff is very important, but that's not all there is - not nearly. Just do science - just do it and stop debating if and the semantics - do some experimentation, with some hacked objectivity, controls, etc. It's a powerful tool: what you discover when you actually try it, whatever it is, will change your perspective, will raise new questions, and will lift up your mind and spirits, guaranteed. I know so much more about the world than many people, simply by doing a bit of exploration through experimentation.

Human curiosity. Embrace it for its nature, not the end goal.

I'm struggling to see how somebody on their own could come up with a non-trivial scientific result that was meaningful in any way.

This is a very dominant attitude but that in itself gives guidance for more alternatives than there would be otherwise.

Naturally some people are better prepared and/or more promising on their own than others having the overwhelming support and encouragement of an established institution.

It's just plain "Nature" after all, naturally.

A certain number of the very most promising individuals are simply not ready for an institution.

That's just plain statistics.

Sometimes the individual themself is not suitable for institutionalization, other times the institution is not suitable for the individual.

Can you give us some examples of what you mean?

ASTM contains some of the most repeatable & reproducible science published. Repeatability & Reproducibility statements are required before the vast majority of material will even be considered for publication. Mainly a committee of leading scientists will carefully conduct the proposed procedures in all of their individual laboratories, before using the data to arrive at an agreed-upon consensus. This has always been a significant effort that would be impossible without highly co-ordinated dispersed team effort. But that's just the publication. Now to some people almost everything in ASTM will always be considered more reliable on the whole than the bulk of everything in Nature, for others it's vice versa. To each his own, I would consider both publications to be equally prestigious even though ASTM almost never names contributors in the pages of its volumes. ASTM scientists participate on a volunteer basis anyway. Publication wouldn't be possible without the bureaucracy, but so many of the actual proven scientific ASTM procedures were completely originated by individuals whether or not they were working in their home institution basically alone, or using their own resources in the equivalent of their own "home".

With the dangerous chemicals I worked with, I always recommended "don't try this at home" myself.

Regardless, some of the most outstanding scientific minds and experimentalists just aren't going to limit themsleves to what is recommended no matter what you say.

But that's besides the point, IIRC since I was a toddler, publication is over-rated.

Plus there are more kinds of industrious people than there are institutions or industries to accept them.

Any attitude which reduces acceptance further can only be expected to reduce chances for overall scientic progress proportionally.

I'm struggling to see how somebody on their own could come up with a non-trivial scientific result that was meaningful in any way.

Richard Feynman at 67, partaking in an inquiry into the space shuttle challenger disaster, dunked some pieces of rubber, taken from a model of the challenger, in ice cold water and observed that they lacked springiness. The full story is fascinating. Other simple, non-rigorous experiments he performed also had meaning and whether they were “non-trivial” is nothing to do with science, that’s political nonsense.

There’s a lot of examples of individuals performing simple experiments that are meaningful.

——- https://lithub.com/how-legendary-physicist-richard-feynman-h...

I believe the point he's trying to make is that he still considers it be science, regardless of the label you've chosen to place on it.

The first step of any scientific study is a lit review, so reading is still science. :)

humbug! boo hiss! Do you go to concerts and critique the scaffolding? :)

And that is not the first step. The first step is to have a curious thought, to seize on it, to rush out to test it. And only then, maybe, you do a lit review, do it more formally, and write it up.

I just was starting to eat Gumbalaya, and I paused. ... I remembered the leftover bit of gochujang chili oil in the fridge from a restaurant, the one I've been trying to find a use for. Surely no! Bayou creole with this already a bit-too-far Korean-Chinese fusion? I couldn't imagine it. And surely then, for science, I had to try ... (it was incredible, but could have been awful - no way to know without trying it). I suppose I should review lit and write it up ...

reading is still science. :)

Umm, no.

Reading is still research.

Time spent reading may lead directly to more science, but it's not always the most prominent path, plus you have to put down the books occasionally and get into action or the research will stagnate because of a thing called no progress whatsoever.

Science is the part that may lead to future publications. Maybe, maybe not.

Often best conducted with the hands, eyes and mind not overly bound or preoccupied with materials previously published.

Remember the default, especially in hard science, is no progress whatsoever, with gradual loss of technology developed during previous lifetimes.

So reading can be most essential to keep previous progress from being forgotten or lost completely.

I say don't stop reading altogether but get into action as much as possible.

-note not my downvote, corrective upvote actually

Don't get me wrong: I think you are right, and I should try it myself. But I was hoping to maybe get some insights from somebody in the field.

I have actually been looking for literature about that, and I don't know (maybe I missed a lot) but it did not really feel like there was a definitive answer to that.

... I should try it myself. But I was hoping to maybe get some insights from somebody in the field.

Yes, of course. Please don't mistake my enthusiasm for some imperative or criticism. I was just taking the opportunity to make a point in HN generally. I look up the existing literature all the time. What a waste of all that effort otherwise!

As we used to say, 6 months in the laboratory can sometimes save you hours in the library.

The most ambitious did both at the same time.

Who wrote that? 100% behind it. Thanks for sharing

Nobody well-known any more.

Probably have to dig through the "literature" ;)

My parents used to use these. I don’t recall if they worked, and I’ve not seen them in quite some time.

https://www.lightbulbs.com/blog/how-do-bug-lights-work

Camping lanterns are still sold with this idea. For instance, I have one of these: https://hardkorr.com/au/product/u-lite-dual-colour-led-lante...

The wavelength of our orange LEDs is 610nm, putting them outside of the spectrum visible to must bugs, but still well inside the boundaries of human vision. As a result, most bugs will not congregate around our orange light because they simply don’t know it is there.

That colour also feels reminiscent of a camp fire, which I've often thought could be related — a bug wouldn't survive long if it flew into fires.

So am I understanding correctly that this confirms the common perception they cited:

Insects use the moon as a celestial compass cue to navigate, and mistakenly use artificial light sources instead

I don't think it confirms that. It seems to be one of the popular theories they investigated. Later they say -

"In both field and lab conditions, insects rarely head directly towards, but consistently fly orthogonal to the light source. This refutes the fundamental premise of an escape response."

"An insect should keep a light source at a fixed visual location for maintaining its heading. Switching light position (Supplementary Fig. 5) shows that insects readily hold the light source on either side of the body."

It makes sense to me. Imagine you were an insect and you would use the moon for navigation. Would you really be flying directly towards moon? No, right? Then how could someone think that insects flying directly towards artificial light source is the basis for the theory that insects use moon as navigational aid?

I think you're misunderstanding GP.

This definitely refutes the theory that insects are trying to escape towards the light, because, as the article shows, insects don't head directly for the light, but instead move orthogonal to it.

But this doesn't mean they can't use moonlight to help with flying. The theory, as I understand it, is that they use a distant light source -- e.g. the daytime sky -- to maintain altitude. There's no reason they couldn't use the moon to do this too.

Again, they would not be flying towards the moon, they'd be keeping the brightest light to their dorsal side. Since the moon is distant, unlike a lamp, this would result in steady flight.

I'm not sure that it confirms whether they use the moon or not, but it seems like a possibility.

Wait, so it could be a parallax thing?

The moon is in practical terms infinitely far away, and no matter how far the insect flies it won't budge and stay as a stationary feature to localize by.

But do the same with a lamp that's only 3 m away, and keeping it in the same spot can only mean flying around it in circles, towards, or away from it, otherwise it'll move around a lot relative to the insect observer.

The spiraling in might also be a kind of vertigo response as well. Normally the moon only goes up or down in your field of vision if you’re adjusting your angle - pitching or rolling. But an artificial light source moves up or downwards if you’re changing altitude but maintaining attitude. That would make flying up past the light ‘feel like’ pitching away from it, which might cause autonomic steering responses, similar to inner ear/visual conflicts causing humans to stagger and fall over.

Okay, something I'm confused about. "Dorsal side" means, as far as I can tell, your back. So if a fly is keeping its dorsal side facing the moon, that means its back is pointing at the moon.

When the moon's directly overhead, this makes lots of sense. Fly goes around wherever. But if the moon's low on the eastern horizon, would we expect flies to mostly be facing upwards, and mostly flying west?

Doesn’t it just make more sense that they orient their movement in relation to the moon? Doesn’t matter what the specific orientation is — if the moon is 3 inches across and sitting in a room, it’s gonna fuck with the insect’s navigation.

Imagine you were an insect and you would use the moon for navigation. Would you really be flying directly towards moon? No, right? Then how could someone think that insects flying directly towards artificial light source is the basis for the theory that insects use moon as navigational aid?

If you're flying parallel to the ground (horizontally), you'd want the moon to be where your back is and you'd have a good change of flying straight. It's like when the kids say that the moon seems to "follow" them.

"Dorsal" means where the top part is, the insect's back, as it were.

What’s so special about keeping it ‘where your back is’? The moon is rarely located directly overhead. Wherever it is, keeping it in a fixed relative position will get you going in a straight line.

The article talks about the ‘dorsal flight response’ being more about the overall alignment to the sky hemisphere, not the moon specifically.

“the brightest part of the visual field has been the sky, and thus it is a robust indicator of which way is up. This is true even at night, especially at short wavelengths (<450 nm)”

What’s so special about keeping it ‘where your back is’?

Since we're to imagine the grandparent flying around like an insect. I imagined them as person flying but with insect wings. Since we're mammals with eyes pointing straight ahead, as opposed with them being on the side of our heads, we'd need some light sensor on our back to ensure we're flying straight at night and keeping the moon above, as opposed to having to look behind every so often to ensure the moon is still there :-)

If your logic is "keep the brightest light source on your left", then for a light source that's nearby (as opposed to "infinitely" far away, like the moon) you'll end up orbiting it.

Depending on your precise navigation logic, you'll either end up with an increasing or decreasing orbit radius. If it decreases, you'll eventually crash into the light source.

That’s my understanding too.

The way I thought about this before was that normally an insect would ‘keep the moon’ on one side to navigate straight, but artificial light messes that up and they end up spiraling around those light sources.

Which seems exactly the behavior that they have demonstrated in the research.

they end up spiraling around those light sources

What I'm struggling to understand is how the insects then reach so close to the artificial light. Why don't they spiral the artificial light from a great distance like 1 metre or 2 metres away? I see the insects hovering like millimetres or centimetres away from artificial light.

See this comment by another user ITT:

Wait, so it could be a parallax thing?

The moon is in practical terms infinitely far away, and no matter how far the insect flies it won't budge and stay as a stationary feature to localize by.

But do the same with a lamp that's only 3 m away, and keeping it in the same spot can only mean flying around it in circles, towards, or away from it, otherwise it'll move around a lot relative to the insect observer.

https://news.ycombinator.com/item?id=39195508

Seems a reasonable explanation to me :)

If I understand correctly part of the explanation is that when they're flying horizontally they need to compensate for gravity by pushing up, kind of like what planes do. If you put them in a place where there's no gravity with a light floating in the middle of a room they'd orbit the light while also getting closer as they're trying to compensate for gravity, and when you put gravity back I guess that produces the weird orbiting we observe.

Haven't seen flying insects since last summer but if I think they kind of lose altitude the closer they get to the light source, which would be when their torso is less horizontally oriented.

Also this is just a guess but I imagine the closer they're to the light source and the larger the contrast between bright and dark is, the stronger is their tendency to get locked into the orbiting path as opposed to flying randomly.

The larger the distance, the more it actually works as a navigational source so you won't see those insects since they are navigating just fine.

The insects you see are the ones that happen to get too close and thus their nav gets 'jammed'.

It's similar to planes navigating by compass. Works great, until you go up to the arctic circle, then you better have another nav source or you too will be flying in circles.

I think the moon theory was almost right, but I didn't see any reference to insects keeping the light source to one side or the other. The researchers seem to think that insects orient as if the brightest thing they see is "up".

I think a lot of the comments are also missing the fact that the moon is an unreliable means of navigation due it not always being present the whole night (or at all), changes brightness, moves around the sky and can be covered by cloud. It is unlikely then that insects would specifically evolve to use it as a means of navigation.

The paper states that it is the general brightness of the sky, even at night, compared to the ground that is the point of reference. So insect point top side at diffuse bright area and bottom side will be parallel to ground.

It seems to me they are using it, but as you mentioned navigation may not be the purpose. There may be none. It may just be that insects that do this congregate and reproduce thus it’s just a mate finding thing that’s evolved. Since insects often have short lives, I’d guess it also explains why they’re always doing it (they need to mate asap).

Might also explain why they don’t go directly to the light but eventually end up there circling it erratically, increased odds of bumping into a mate.

The paper mentions that the insects enter stall conditions, maybe due to the banked orientations, sometimes and then recover. This would explain erratic behaviour without any mate present.

More like using the sun/sky to adjust their attitude of flying. Everyday, not only when moon is visible.

Insects use the moon as a celestial compass cue to navigate, and mistakenly use artificial light sources instead

I think that was one of the theories being investigated by this research. The paper demonstrates that it is the actual light (of the moon or stars or sun or artificial source) they use to orientate themselves in the horizontal plain BUT that is not navigation. With a "tilt" in their orientation they will fly in circles around the light but this tilt also causes inefficiencies in their actual flight mechanism so will cause erratic directional stability as their flight path rapidly changes their spacial relationship to the light source. Whatever their navigation imperative (heat, cold pheromones,smell, sight, sound) will be affected by this spacial relationship instability.

I had a really weird observation. Do you know how in the summer flies tend to enter rooms and circle the middle of it (where usually the turned off light fixture is)? And they seemingly can't or don't want to find open window to leave the room?

At one point for unrelated reasons I replaced light fixture in my room with more than 200W worth of strongest E27 Philips LED lightbulbs I could find (20*1521lumen).

Few flies gathered in the middle of the room as usual during the summer day. Then I turned on this light just out of curiosity. The flies dispersed within seconds, suddenly perfectly capable of not flying in circles. I don't think it was the heat or the discomfortably bright light just scaring them off. Even this amount wasn't as bright as sunny day. I think more light and more distributed light (not just comming from the direction of the window) fixed their navigational abilities somehow.

Flies easily fly through the window if it's substantially brighter than the room.

Not in my experience. The walls were dark. And the window was bright occupying half of the surface of one wall. They still flew in circles.

I think it might be what other commenters are pointing out. That flies consider the brightest direction to be the sky, but if it's to the side (with respect to gravity) it messes up their navigation.

I wonder now, do flies ever venture inside of caves?

I’m curious: how are those 20 bulbs installed? You got a single fixture with 20 bulbs??

Just screwed 20 lightbulb sockets to a board and connected them with wire.

Fixture adapter like this maybe? https://a.co/d/iOgDKZf

This actually squares with the study, no? I mean, when they are inside - and it's my experience as well - they might take the window as the main source of light and think that's the sky, so they start to fly in circles.

The observable effect is true, but I don't think it squares. Circles below the ceiling in the middle of the room aren't perpendicular to the window as a light source.

I see this mostly with one particular type of fly that just loves going around light fixtures, maybe they're sensitive to the EM spectrum rather than visible light?

That's probably it. When the "sky" doesn't align with gravity they get confused.

I like bright lights as much as anyone else, could you explain how you got a 20x fixture set up in your room? I've heard of 500 watt E38 mogul fixtures, but not 20x mini ones

I just screwed 20 cheapest lightbulb sockets to a board and connected them with wires.

I was under the impression they confuse lights for stars and it messes with them. So if you simulate the sun the probably don’t get confused. You can but red spectrum lights that also are supposed to be bug friendly

I notice that clouds of gnats will gather at the boundaries between light and shade. Other insects may adopt similar behaviors.

I have a few theories, these are my own speculations, so I could be wrong.

I speculate that the flies rely on a phenomenon called "optic flow" for navigating around obstacles. Basically the rate of feature movement perceived on each side of their head/compound eyes determines proximity to objects. Their vision is very blurred, so features need to be quite large, or at least contrasting. If you have a dimly lit room, with white walls, the whole space will appear mostly featureless to the fly, until they get close enough to the wall, and thus fly around in circles.

Perhaps they also use a fixed contrasting object as a reference point, like the light fixture (turned off) and return to it if they veer off too far into the "featureless void". If you turn on the light, the perceived illumination in the space is inverted. The light makes previously invisible objects around the room more contrasting for them to navigate about and to fly closer, even land.

So one could optimize an outdoor light location design to reduce insects?

Like for example an outdoor dining terrace?

In my experience... kind of. Light isn't the only thing they're attracted to so you'd have to optimize distance and cover different variables for different bugs.

One fun thing you can do is relocate small swarms of bugs with a torch to another light source. So if you're being pestered, turn on a torch... and slowly walk the bugs to a different light source (a distant lamp for example). Then turn off the torch and walk back to where you were. The light will keep them there.

Would or could that be automated? We are hounded from late spring to the fall by all kinds of flying nasties at our front porch. Some led string that moved them all away would be awesome!

would be interesting to try, it's easy to walk over because you can watch the swarm but if you've got a slow moving light on a string I could imagine it working

a bug zapper is a lot easier

How about a light on a rail? we could race them around a track taking bets.

I’m not sure if there’s interesting optimization to do. Simply: bugs are attracted to light, light=more bugs, no light=fewer bugs. Motion detectors, for example, can make it so that the light is only temporary and you don’t get those moth parties.

bugs are attracted to light

Isn't the takeaway from this study that they aren't really, but rather that once they happen to come close to it they cannot get away from it anymore?

The effect is the same (for the purposes of an outdoor dining area), and I believe that's what they were referring to. Perhaps a better way to word it would be: bugs will go towards a local light.

What do you want to reduce further, a large fraction of insect-species are already getting extinct across most of the developed world.

May I inquire where do you live? Urban or rural?

Maybe some sort of directional lighting funnel that attracts insects on one side and the guides them out in a direction away from humans?

Bug bulbs: https://www.amazon.com/Edison-A19-14W-LED-Light/dp/B089QXZ8R...

Still seems a bit tricky unless you have a ton of land?

Only one experiment that we know of has tracked moth trajectories to lights over long distances, and found only 2 of 50 individuals released 85 m from a light source ended their flight their flight there

I realize this is a small sample, but seems to suggest that if you placed a lamp in a field that 4% of all bugs within a ~football field in every direction would end up near it. I feel like that may mean placing a lamp 10 feet from where you are going to eat (or whatever) may actually attract more insects to that general area.

But I'm having trouble understanding some of their methods

It’s always amusing in the garden center at Home Depot looking at the enormous spider webs (and the fat spiders) around their sodium vapor lamps. It must be that the number of calories required to produce bioluminescence to create this effect must be greater than the calories that could be derived from hunting that way. But if someone else provided that free energy for hunting…

Interesting. I sometimes wonder how they end up near the lights: there wouldn't seem to be a light source at night for most of their evolution. Maybe they used the moon in the background.

But is it correct to assume that, if something is naturally possible (e.g., bioluminescence), and provides significant evolutionary advantage, the species will evolve it?

If so, why are we the only intelligent ones (so far)? Why didn't chimpanzees, sharing a common ancestor with us 7 million years ago, evolve intelligence?

My guess is that apes with similar interests started socializing because it was enjoyable and more stimulating than hanging out with apes who could not/would not perceive the nuances of the world the same way.

My guess is that spiders build webs in many places, but only the successful ones remain. In other words, survivor bias.

This spider-webs-covering-lights phenomenon is replaced over and over and over in every Northern Ontario community. It was unreal when I worked at a camp on Lake-of-the-Woods.

I am sure there was enough webs that you could stuff several pillows with them.

Or you are observing evolution in action. A bioluminescent spider would likely be an easy target for birds or bats. One by the lamp is not because hunters have simply not adapted yet. Or maybe, spider webs used to be enormous and profitable everywhere, only that insects dying globally makes them profitable now only in those light spots.

This seems like a pretty important finding, entymology's version of cracking Fermat's Last Theorem. I wonder if there's a Nobel category for entymology.

I read about this explanation years ago. It's not novel. I don't remember where, though... It might have been from Feynman.

This explanation is in a Cricket Magazine I have from the mid-80s, so perhaps there's something new here also?

The novelty is that they tested this one theory instead of just proposing it as an explanation.

The introduction of this paper lists some other explanations that you may or may not have seen in the past and it says some have been disproven and some have not yet been tested.

The paper lists some other explanations and references the papers that analyzed them. Maybe the paper presents a novel convincing technique, but it is not like they are the first to study the behavior.

I have a feeling the stars are used by insects to navigate in pitch dark environments. And the lack of stars may be causing a large decline in insect population.

Making a road trip in the light polluted northeast america, I was looking for stars in the darkest of forested of environments, and I could not find any stars anywhere. I am not sure if the clouds were there. But I realize I have not seen stars in a long time.

It depends on what you count as using stars. Insects don’t have good enough eyes to see individual stars, but dung beetles can see the Milky Way and use it for navigation.

I hope you get the opportunity to see them soon. I live in the south and I enjoy them, although the "seeing" (astronomy term) is poor here due to the jet stream.

I'd argue that, based on what this paper is discussing at least, it'd be pretty impossible for them to use stars to navigate. I'm not sure what they'd do in pitch dark environments but if they're using either the sun, moon, or artificial light to help them navigate, I highly doubt stars would even register/be detectable to them.

I wonder if spiders have fights over who gets to build their net next to that big, bright lantern. Those must be prime real estate for them.

Some (or most) spiders are territorial and yes, they do fight for hunting ground.

Makes sense. Thanks for clearing that up! I really do learn something new every day.

It'a a purely legal form of combat. Lawsuits and contract disputes.

A theory I have is that some may use it as Schelling point [1] to coordinate. For reproduction but maybe other things too.

Similar how the environment conditions after a rain can be the catalyst for ants nuptial flight [2].

[1] https://en.wikipedia.org/wiki/Focal_point_(game_theory)

[2] https://en.wikipedia.org/wiki/Nuptial_flight

What would the shelling point be before the advent of artificial light though? Can't be the moon. Or do you think it evolved on the human time scale?

Yeah, I was referring to full moon. Maybe in combination with other environmental variables. Why can't it be?

If that's case the behaviors relying on it have been quite fucked up for some time.

Fascinating that it has nothing to do with desire, which has tended to be our go-to as humans stretching back in particular to mythology and even antiquity (eg Aristotle IIRC: “things fall back to the ground because they have a desire to do so”)

You could still see it as a desire that is being highjacked by our artificial lights. It's an unintentionally wire heading, where our desire for light defeats the insects desire to trust it's 'instruments'.

Under what conditions would you call this behavior "desire"? Would we need to demonstrate the impossible, that insects have a sense of self and free will?

Do insects desire food, or does the intensity of certain smells simply compel their mouth parts to start moving in a certain way?

How is it compatible with the times of the day/year when the sun is absolutely not "up there" but closer to the horizon?

The insects still orient themselves towards the sky, as it's the brighter hemisphere. They're not locking directly onto light sources, just using them as a cue for orientation. But that fails when the reference point is not distant, as with an artificial light.

Thanks! I understand better.

Cool study, I've got this question before from my 7yo and had no idea :P

If I'm reading it correctly, insects don't fly toward the light, they turn the front of their body toward it. Under natural light, this helps them fly correctly ("maintain proper flight attitude and control"), but with artificial light they end up just constantly flying around the light source?

Not the front part, the upper/back part. Otherwise, yes.

they turn the front of their body toward it

Google says dorsum is "back or top (dorsal) side". Kinda makes sense that they'd assume light means up.

and how about moonless nights? or thick clouds?

seems there should be alternative navigation ways..

There may be. I recall a documentary where they were studying homing pigeons. Placing magnets on the pigeons would throw off their navigation, but only on a cloudy day, suggesting that any magnetic navigation they have is redundant with solar navigation.

Read a bit of it and it does make sense I guess! Looking it up it seems as though insects generally don't have the fancy ear/inner ear that we have as humans seems to sense gravity and velocity through inner ear and pressure against our skin (across our whole body).

Considering that insects don't have our fancy inner ear and can sense touch/pressure on a surface but cannot use this in flight, I guess it does make sense that they'd need some other way to orientate themselves; why grow another organ/sense when eyes already do the job! (Until humans come along and ruin it by discovering fire).

So Tesla's will do this? /s

The paper tries to make it sound like it solved a long-standing mystery, while it basically just confirms the most obvious explanation: Insects use artificial (close) light sources like a natural (distant) light source for navigation, which makes them eventually spiral towards the light most of the time.

The methodology and resulting graphics are interesting, but the underlying geometry of the effect is not really new or surprising.

Yeah, I feel this was taught to me in primary school or something.

Does this explain why bugs seem to swarm at sunset? Because the sun is lower towards the horizon it brings the bugs towards the ground?

Some aquatic insects fly around sunset because the polarization of the light makes it easier to see bodies of water to land on

  And there's this moth outside my kitchen door
  She's bonkers for that bare bulb
  Flying round in circles
  Bashing in her exoskull
  And out in the woods she navigates fine by the moon
  But get her around a light bulb and she's doomed

  She is trying to evolve
  She's just trying to evolve


  Gunnin for high score in the land of dreams
  Morbid bluish-white consumers ogling luminous screens
  On the trail of forgetting
  Cruising without a care
  The jet set won't abide by that pesky jet lag
  And our lives boil down to an hour or two
  When someone pulls a camera out of a bag

  And i am trying to evolve
  Trying to evolve

This reminds me of one of my childhood's favorite activities in Vietnam: catching water bugs late afternoons. I think they are https://en.wikipedia.org/wiki/Lethocerus_indicus, but I might be wrong. That was in the 80s where Vietnam was very underdeveloped. There weren't many street lights and they were usually dim. Our house was right next to a newly built road (which eventually became a highway). That was one of the only few roads with bright street lights. The brightness of the newly installed street lights didn't attract just us kids, but also these water bugs from the rice field on the other side of the road. Once day we were told that these insects are actually edible! I and a few kids on the same block started capturing those insects, put them in jars, and brought them back home :)

So now we can blame the insects bad attitude rather than our artificial lights.

I've always noticed that sun rays through monofilament fishing line attract dragonflies, yet fails to do so on overcast days.

ive seen all types of flying animals fly to a light source, and ive observed a family of lizards feed upon the bug who are attracted to the lamp. the parents taught the baby lizards who now are teenagers. once a big grasshopper flew into the light and passed out and a lizard saw it happen but didnt go down and eat it. lights are on at night and cold nights lizards are dumber and lazier than usual.

The dorsum to the light fact is interesting. And now, watching some random moth to the light vids on Youtube makes more sense to me [1].

[1]: https://www.youtube.com/watch?v=OhNpOsTUqzA

Contrary to the expectation of attraction, insects do not steer directly toward the light. Instead, insects turn their dorsum toward the light, generating flight bouts perpendicular to the source. Under natural sky light, tilting the dorsum towards the brightest visual hemisphere helps maintain proper flight attitude and control. Near artificial sources, however, this highly conserved dorsal-light-response can produce continuous steering around the light and trap an insect.

previous discussion https://news.ycombinator.com/item?id=35592654 128 comments

Well one other aspect of this research springs to mind.

Most "bug zapper" design are wrong. It should consist of a light source and a single grid perpendicular to the light source rather than surrounding the light source.

The light source should also be constantly varying to ensure the insects' tilt (and hence their circling behavior) will also change the radius of their circles.