[HN Gopher] Why flying insects gather at artificial light
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Why flying insects gather at artificial light
Author : pseudolus
Score : 188 points
Date : 2024-01-30 17:18 UTC (5 hours ago)
(HTM) web link (www.nature.com)
(TXT) w3m dump (www.nature.com)
| andrewgioia wrote:
| 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?
| sho_hn wrote:
| Not the front part, the upper/back part. Otherwise, yes.
| rootusrootus wrote:
| > 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.
| huydotnet wrote:
| 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
| elpocko wrote:
| > 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.
| imbnwa wrote:
| 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")
| rcoveson wrote:
| 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?
| wddkcs wrote:
| 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'.
| jjslocum3 wrote:
| 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.
| smaddox wrote:
| I read about this explanation years ago. It's not novel. I
| don't remember where, though... It might have been from
| Feynman.
| dmd wrote:
| This explanation is in a Cricket Magazine I have from the
| mid-80s, so perhaps there's something new here also?
| topherclay wrote:
| 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.
| LudwigNagasena wrote:
| 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.
| scotty79 wrote:
| 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.
| paiute wrote:
| 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
| darkwater wrote:
| 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.
| kevin_thibedeau wrote:
| I notice that clouds of gnats will gather at the boundaries
| between light and shade. Other insects may adopt similar
| behaviors.
| zuzun wrote:
| Flies easily fly through the window if it's substantially
| brighter than the room.
| sschueller wrote:
| So one could optimize an outdoor light location design to reduce
| insects?
|
| Like for example an outdoor dining terrace?
| micromacrofoot wrote:
| 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.
| Simon_ORourke wrote:
| 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!
| lawlessone wrote:
| How about a light on a rail? we could race them around a
| track taking bets.
| micromacrofoot wrote:
| 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
| fasthands9 wrote:
| 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
| bee_rider wrote:
| 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.
| stinos wrote:
| _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?
| joemi wrote:
| 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.
| paiute wrote:
| Bug bulbs: https://www.amazon.com/Edison-A19-14W-LED-
| Light/dp/B089QXZ8R...
| throw_pm23 wrote:
| What do you want to reduce further, a large fraction of insect-
| species are already getting extinct across most of the
| developed world.
| alxmng wrote:
| 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?
| beedeebeedee wrote:
| Some aquatic insects fly around sunset because the polarization
| of the light makes it easier to see bodies of water to land on
| tomxor wrote:
| So now we can blame the insects bad attitude rather than our
| artificial lights.
| nashashmi wrote:
| 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.
| r2_pilot wrote:
| 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.
| chankstein38 wrote:
| 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.
| tzs wrote:
| 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.
| codetrotter wrote:
| 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
| mapreduce wrote:
| 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?
| SamBam wrote:
| 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.
| moffkalast wrote:
| 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.
| jameshart wrote:
| 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.
| Retr0id wrote:
| 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.
| rdtsc wrote:
| > 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.
| jameshart wrote:
| 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)"
| jgilias wrote:
| 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.
| pavedwalden wrote:
| 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".
| mapreduce wrote:
| > 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.
| codetrotter wrote:
| 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 :)
| Berniek wrote:
| >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.
| teeray wrote:
| 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...
| patall wrote:
| 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.
| blauditore wrote:
| 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.
| martopix wrote:
| Yeah, I feel this was taught to me in primary school or
| something.
| henearkr wrote:
| How is it compatible with the times of the day/year when the sun
| is absolutely not "up there" but closer to the horizon?
| krylon wrote:
| 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.
| lukan wrote:
| Some (or most) spiders are territorial and yes, they do fight
| for hunting ground.
| krylon wrote:
| Makes sense. Thanks for clearing that up! I really _do_ learn
| something new every day.
| svilen_dobrev wrote:
| and how about moonless nights? or thick clouds?
|
| seems there should be alternative navigation ways..
| Berniek wrote:
| 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.
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