[HN Gopher] How many flies are in my apartment?
___________________________________________________________________
How many flies are in my apartment?
Author : maverickleopard
Score : 214 points
Date : 2021-06-17 02:15 UTC (1 days ago)
(HTM) web link (saml98.github.io)
(TXT) w3m dump (saml98.github.io)
| 0xBA5ED wrote:
| A tip if you have an annoying fly in your house that's hard to
| swat. Turn off all the lights except the bathroom. In a few
| minutes it'll fly in. Close the door and it's mano-a-mano.
| pjerem wrote:
| Works well with mosquitoes too. I just let them do whatever
| they want in the bathroom once the door is closed.
|
| However I would admit that switching lights on at 3AM and
| deliberately opening all the doors for the light to be seen is
| not something my family appreciate. But, at least, I'm their
| hero.
| Tempest1981 wrote:
| Also works with a computer display in a dark room. Until you
| hit the display going mano-a-mano.
| ahartmetz wrote:
| From experience: about 5x as many as you think
|
| Story: I was living in a large flatshare that was plagued by
| flies from nearby horse stables. We were organizing a decent
| sized party (maybe 40 guests). In the afternoon, we had 15ish
| items of food that needed to be stored for a few hours until
| guests arrived. At first we considered covering all the food
| (creating work and waste of aluminum or plastic foil), then I had
| the idea to kill all the flies in that room and close the door.
| We saw about four flies. In the end we killed about 20 before we
| declared the situation good enough. I don't recall if there was a
| last fly that we eventually killed, or that we eventually gave up
| on killing. It took half an hour or so.
| solarkraft wrote:
| If you're already interested in flies, check out how they behave
| in nature. They can be quite territorial about their leaf or
| stick and fights between these agile little beasts are
| fascinating to watch (extremely quickly orbiting each other).
| mannykannot wrote:
| Levy flight foraging hypothesis:
| https://en.wikipedia.org/wiki/L%C3%A9vy_flight_foraging_hypo...
|
| The scent-tracking mode used here seems to be a sort of variant,
| in which the long legs are not chosen randomly.
|
| WRT the insect density decreasing as some fly away: in reality,
| others will arrive at approximately the same rate, keeping the
| density approximately the same, so it is probaby more realistic
| to put a box around the simulation, e.g. by reversing the
| direction of those that have moved away to the point that they
| would be several time-slices away from entering the window even
| if they flew back in a straight line.
| pacman2 wrote:
| A fly is unlikely to fly randomly.
|
| https://en.wikipedia.org/wiki/L%C3%A9vy_flight
| jjfine wrote:
| go to the store and buy a removable screen dude. i got one in
| chinatown for like 5 bucks.
| lolc wrote:
| All these models ignore how insects actually zero in on a smell.
| For a fly outside, the source of the smell is the gap in the
| window. What looks like random direction changes is actually a
| search pattern for that source.
| rossdavidh wrote:
| There is presumably also a falling-off of the signal with
| distance. Flies may have a good sense of smell and all, but
| it's not infinitely good. Which is too bad, because if they
| did, then all the flies in NYC (or I suppose maybe the world)
| would all be in one big clump near the best (to a fly) smelling
| object. Although I guess if you were that object, then it would
| be not as good.
| lolc wrote:
| Sure, the inverse square law applies to smells as well.
| JadeNB wrote:
| > All these models ignore how insects actually zero in on a
| smell.
|
| It seems to me that the author is not ignoring that:
|
| > While the flies now obey the laws of aviation, there's still
| something that seems missing. Normally, flies want to get
| indoors. They need to get indoors. So to simulate this, I added
| an attractor (maybe a rotting piece of fruit) at a position A
| indoors to lure the flies.
| lolc wrote:
| The model where the fly knows where the source of the smell
| is located the weird outcome of the flies targeting the pane
| in the middle instead of the sides where the smell escapes.
| pelasaco wrote:
| You are right. Even though it is probably a great exercise to
| improve your skills as data scientists, I'm afraid that without
| understanding how the insects actually "work/think", it is
| nothing more than garbage in, garbage out (GIGO).
| TchoBeer wrote:
| I don't know how intentional it was but that's a great roast
| on data scientists.
| teddyh wrote:
| Slightly related: Anemotaxis
| https://www.youtube.com/watch?v=hIqmIQbQkW8
| lolc wrote:
| Thanks, that was actually the screensaver I was thinking of
| when I wrote my comment :-)
|
| But I don't actually know whether flies do use this pattern.
| btbuildem wrote:
| Very good point -- and that's why they find their way inside so
| easily, but look really dumb trying to find their way out.
|
| Same principle behind a DIY fruit fly trap (glass of juice with
| a plastic cover with a few holes poked in it).
| josefresco wrote:
| Then why only two?
| pelasaco wrote:
| an interesting research in this area
| https://journals.plos.org/plosone/article?id=10.1371/journal...
| lolc wrote:
| Thanks, that was an interesting read on the topic!
| kzrdude wrote:
| I tried showing the flies using
| matplotlib.animation.FuncAnimation in a notebook, animating even
| 1000 frames is slow and it warns the animation becomes too large.
| Maybe there's a better way to do it? Preferably in a notebook
| interface.
| kzrdude wrote:
| I ended up writing some very rudimentary HTML canvas +
| javascript drawing code into the notebook and for my purposes
| it's fast and does the job. Just to note to others, that this
| is a possibility within a Jupyter notebook.
|
| One obvious benefit is that it can start rendering "live" and
| continuously and doesn't have to generate the whole animation
| before starting to show it.
| immmmmm wrote:
| pyqtgraph is a nice matplotlib replacement when speed matters,
| but doesn't work in a notebook
| mhb wrote:
| Fly salt guns:
|
| https://www.bugasalt.com/
| aetherspawn wrote:
| This would be an interesting thing to prove with OpenCV
| mschuster91 wrote:
| Flies are small... you'd need a lot of light, multiple angles
| and good cameras/lenses to decently illuminate the flies, which
| has the problem that all the light will only attract more
| flies.
| nly wrote:
| Is this really true? I mean we've had tech like Hawk-Eye[0]
| for a couple of decades now.
|
| Surely we cameras good enough for fly tracking technology in
| 2021?
|
| [0] https://en.wikipedia.org/wiki/Hawk-Eye
| yarcob wrote:
| That camera system tracks a single, largish object in
| perfect lighting.
|
| I think the biggest problem with insect tracking is focus:
| They are so small that they can only be recognized if they
| are perfectly in focus, so you probably can't track them in
| 3D volumes.
|
| Maybe you could track them with clever lighting tricks. Eg.
| illuminate room with very bright light coming from the
| side, with a black wall, so that mosquitos show up as
| bright spots in the video.
| aetherspawn wrote:
| I think it would be fine if you tracked only the flies that
| entered or exited through the small hole in the wall, ie not
| tracking the whole room just a tiny corridor.
|
| So yes, you know the delta-fly(er) but not the number of
| flies.
| anyonecancode wrote:
| And if there were a small door over the hole, that opened
| only to allow fast moving flies to go through it from one
| direction and slow moving flies to go through it in the
| other...
| OJFord wrote:
| Based on my experience, those flies need to be less like jittery
| dots, and more like kamikaze pilots, hurtling themselves from one
| side of the simulation to the other, repeatedly.
| mig39 wrote:
| Really interesting work. I love the different models of how a fly
| moves around. This jumped out at me, though:
|
| >If we take a look at the animation now, we can see the flies
| look slightly more realistic (if not still a bit spazzy)
|
| Is "spazzy" a word that's used in different regional dialects of
| English as a term to just mean jittery? In most of the places
| I've lived, it's an offensive word.
| laputan_machine wrote:
| Uh oh, sounds like they need to be sent to the gulags for re-
| education, then. Report the site to GitHub and I'm sure they'll
| scrub this horrifying prose.
| mig39 wrote:
| huh? It was a legit question. I've lived in a lot of places
| with different dialects of English. Where a term in one place
| is seen as harmless, but means something completely different
| in another.
|
| In this case, I've never heard "spazzy" used other than as an
| offensive term.
|
| Your reaction seems more Reddit than HN, though. So you have
| that going for you.
| rrrrrrrrrrrryan wrote:
| https://en.m.wiktionary.org/wiki/spaz
|
| Seems like it is indeed much more offensive in the UK. I've
| never heard it used to mean "stupid" or "incompetent" in
| America. Here, it describes someone who might be
| scatterbrained, unorganized, eccentric, and a bit hyperactive
| or frenetic, but not necessarily unintelligent - you might
| describe your professor as "a bit of a spaz" without anyone
| taking offense, though you probably wouldn't say it to their
| face.
| rossdavidh wrote:
| "Spazzy" or "spastic" is not especially offensive in the US,
| although I suppose given our ever-escalating sensitivity it
| soon will be. It mostly just implies "given to spasms", which I
| suppose is the origin. More generally, it implies not terribly
| well-organized in behavior. A person might say it of their own
| behavior without meaning anything exceptionally bad.
| morelisp wrote:
| It has been offensive in the US since the 90s. It just gets
| used anyway anytime there's some "anti-PC" movement, along
| with "gay" to mean "bad", the r word, sudden spikes in the
| use of "niggardly", and so on. Like those, its offensiveness
| does not come from offense taken by the person/thing it is
| proximately describing.
| Slump wrote:
| I've only heard it used as a synonym to "jittery" or hyper-
| active in my region of the states (mid-west). Good to know it's
| considered offensive in places, not that I really use the word.
| I had a colleague in school that had the nickname of "spaz".
| Mostly it was used ironically because they were super laid back
| all the time.
| sp332 wrote:
| I remember thinking that the UK has a much more negative
| connotation for "spastic" than the US. In the US it's still
| pejorative but something you could say casually.
| pharmakom wrote:
| Is it better to leave windows open so flies can escape or closed
| so they never come in?
| Black101 wrote:
| Ive left two windows open almost constantly for a month during
| the summer and the flies were not that bad.
| Aachen wrote:
| Window closed means no flies could ever come in, whereas with
| an open window it's a possibility. So purely from a statistical
| point of view...
|
| I've never noticed the number of insects reducing from open
| orifices, only increase, presumably until it's the same number
| per m3 as outside (or higher if you have food out, perhaps). I
| won't rule out that there might exist configurations where
| flies are more likely to fly out of than in to, but aside from
| conical shapes designed to do that (i.e. not regular windows),
| has anyone ever noticed that opening a window reduced the
| number of insects inside?
| Mordisquitos wrote:
| If your windows open outwards, windows open, no contest.
|
| If however they open inwards like mine, open sounds good in
| theory... but you may end up more frustrated at idiotic flies
| buzztapping against the interior side of the glass time and
| time again, rather than flying around it and getting the hell
| out. Might as well keep the windows closed and accept the flies
| are here to stay rather than living in false hope while new
| ones keep buzzing in.
| codetrotter wrote:
| Open windows for air, but have a finely masked net covering the
| opening so insects don't get in.
| purplecats wrote:
| Not sure that answered the question properly
| nsomaru wrote:
| it makes the question not exist any more, same thing.
| fmax30 wrote:
| This is the norm in the south asian country I come from.
|
| But ever since I moved to the EU, there have been no nets,
| then again there are noticeably fewer flies here too.
| vbezhenar wrote:
| In Kazakhstan we're using nets because of mosquitos. Flies
| are not a real issue, they're a nuisance, but not a big
| deal. Mosquitos on the other hand are real night-killers.
| Few of them might keep me awake until sunset with their
| buzzing. Of course preventing flies is a good side effect.
|
| In South Asia, I could imagine that mosquitos are more
| dangerous because of diseases they transmit.
| AlgorithmicTime wrote:
| Also the norm in the US. All my windows have screens built
| in.
| masklinn wrote:
| Also less mosquitoes, and the drier air makes airflow
| somewhat less of a living requirement: iirc screen doors
| are also ubiquitous in the (humid and hot) US south, much
| less so in the north.
|
| window and door screens do absolutely exist in europe, but
| they're definitely uncommon.
| TeMPOraL wrote:
| It's becoming increasingly common where I live (Poland).
| We've installed nets in our last apartment, and the current
| one came with them already in place.
|
| There may not be that many flies in the EU as there are in
| South Asia, but there's enough of them to be annoying. Then
| there are mosquitoes, moths, wasps, bees - and the very
| bugs I've been installing these nets against - _hornets_.
| Before the net, we 'd get 3-5 hornet visits per season.
| Running around the house late at night with an improvised
| flamethrower got tiring very quickly.
| StavrosK wrote:
| Okay, first of all, tell me more about this flamethrower.
|
| Also, when you say "nets", do you mean "screens", ie on
| the windows?
| TeMPOraL wrote:
| > _Okay, first of all, tell me more about this
| flamethrower._
|
| Just a lighter, a spray can, and steady hands. I know
| you're probably disappointed, but simplest solutions do
| work best :).
|
| (To be absolutely clear: I only use this against wasps
| and hornets, and only in situations where there's no safe
| way of shooing them back out through a window.)
|
| Operation: hold the lighter in front of you, light the
| flame, spray above it. Aim for sub-second bursts of flame
| - you don't want anything in the room to heat up. Never
| let the flame come close to any highly flammable surface
| (like drapes, or aforementioned mosquito net).
|
| Tactics: against hornets and wasps, I shoot either below
| it, or at it directly. Shooting below, the rising hot air
| will confuse the bug, possibly stun it for a moment.
| Shooting at it, a sub-second burst is enough to burn off
| is wings, at which point you can finish it off using your
| favorite percussive maintenance tool.
|
| Equipment considerations:
|
| - I tend to use cheap, widely available flint lighters. I
| have experimented with gasoline and butane (high-
| pressure) lighters before, but IIRC, they didn't work
| well.
|
| - For fuel, I use a deodorant. In the past, I've also
| used a hair spray - it's a good choice, because it
| enables a third mode of operation: _cold mode_. Because
| hair spray is viscous, hitting a bug with it is likely to
| clog its breathing apparatus and glue its wings, allowing
| you to safely apply the killing blow. I found it useful
| in a tent[0], where you absolutely do not want to play
| with an open flame of any kind. Anyway, any kind of spray
| with a flammable mixture will work, but pay attention to
| the possible combustion products. I do _not_ recommend
| going for pressurized butane gas directly - it won 't
| combust fully, and you'll be cleaning soot from every
| solid surface near you (ask me how I know).
|
| I've been thinking about building/3D-printing a mount to
| operate the flamethrower single-handed, but to be honest,
| using two hands gives greater control, and the optimal
| distance between the lighter and the spray can varies
| with the type of spray can and environmental conditions.
|
| > _Also, when you say "nets", do you mean "screens", ie
| on the windows?_
|
| Yes. I buy a box with a fine mesh net, which I cut down
| to size and attach to the inside of the window using
| provided mounting strips (adhesive on the window frame
| size, velcro on the net side). We call this "moskitiera"
| (mosquito net). For balcony doors, there are variants
| with the net split in half and held together with magnets
| - so you can walk through it, and it'll close behind you.
|
| --
|
| [0] - I was once on a two-week camping trip where we were
| constantly assaulted by swarms of wasps. We didn't know
| until later that it was because there was a hive under
| the building near our site. The organizers of that camp
| actually funded me a supply of hair spray, and designated
| me as the camp's exterminator. The "cold mode" was useful
| for cleaning out tents every couple hours. After we left,
| the owners of the building decided it's too much hassle
| to clear out the hive, and burned the building down.
| StavrosK wrote:
| _takes notes furiously_
| Nux wrote:
| Grew up near a forested area by the Danube river.. everyone
| and their dog had nets on their windows else the mosquitoes
| would turn your life into a nightmare.
| only_as_i_fall wrote:
| Dont the windows have screens? In the US pretty much every
| window has a permanent screen outside the panel for this
| purpose...just assumed it was the same in europe
| pvaldes wrote:
| Not in south of Europe unless is a mosquito disco
| location. One of the main purposes of windows is to see
| out. The more transparent, the better.
|
| Another factor is the light level. If you have a lot of
| days with rain or low light, like UK or many other places
| have, nets reduce even more the level of light entering
| in the house. Lacking of a lot of the dangerous mosquito
| borne diseases than tropical places have, the cons weight
| more than the pros. Would be seen as a better deal in
| California for example, where the extra shadow is
| welcomed.
|
| And finally there is some inertia provided by cultural
| factors. For Dutch allowing everybody to see your room by
| default (don't have anything to hide here) is a cultural
| post-war thing also.
| only_as_i_fall wrote:
| Idk I've just never even considered losing light because
| of the screens, it's so little.
|
| Maybe I'm just used to it.
|
| Also it's not only like a cultural thing, I legally had
| to put screens in every window of my house before it was
| able to be occupied. Just an anecdote...
|
| It's weird how we never question things like that.
| OJFord wrote:
| FWIW that applies to a lot of your 'codes'. Obviously we
| have regulations too, but it's bizarre (from an outsider
| perspective) how much it comes up in US television, or
| online, and (and in part it seems due to) the extent of
| it.
|
| Regarding light - leaving aside however much it blocks
| light for illumination purposes, what about seeing out? I
| want to look out of the window, not look at a mesh all
| but completely obscuring the view.
| jdmichal wrote:
| The mesh material is extremely thin. As long as you're
| focusing past it, you don't see the mesh itself. Just
| maybe the color of it, which is why black mesh is a
| popular color.
| smrq wrote:
| I have a mesh missing on one of my windows. For over a
| year after moving into this house I literally couldn't
| remember which one without looking up close. It's just
| that unobtrusive.
| astura wrote:
| When I lived in Europe there were no screens on the
| windows.
|
| However, there were also pretty much no bugs; we kept the
| windows and doors open regularly without an issue - if
| you tried that were I live now in the US you'd have flies
| inside making a racket and be eaten alive by mosquitoes.
| jdavis703 wrote:
| In California there's a decent amount of homes without
| screens. I've lived in two apartments that had no screens
| (one was a fire escape, the other opened outwards and had
| a latching mechanism that made it impossible to add a
| screen).
| nicoburns wrote:
| I've pretty much never seen a screen in the UK. I think
| they might be more common in hotter countries further
| south.
| morelisp wrote:
| They do not, and it's unfathomable why. One of the first
| things I did after moving to Berlin was put screens on
| our major windows. My European friends constantly
| complain about insects coming in (wasps are a big
| offender in Berlin - and technically you can't kill them)
| but for some reason never just put up a screen.
| yarcob wrote:
| Maybe because screens make the appartment darker?
| Tempest1981 wrote:
| Fortunately, the sun is getting brighter
| only_as_i_fall wrote:
| I mean generally you can't tell from more than 5 feet
| away so...idk seems like a minor difference
| zimpenfish wrote:
| > They do not, and it's unfathomable why.
|
| Our current windows pivot in the middle which makes a
| fixed screen impossible.
|
| (They do have a "pane inside" mode which would let you
| put a screen on the outside but we're 3 floors up and it
| would be a bit tricky, not to mention inconvenient when
| the temperature drops.)
| morelisp wrote:
| I can see this being an issue, though everyone I know has
| some variant of the standard "German window" (https://2.b
| p.blogspot.com/_gv8PbeT2Ktk/TDiZRMA5oGI/AAAAAAAAA...)
| where they work fine.
| OJFord wrote:
| Because I don't want some ugly thing strapped to my
| window?
|
| Because I want to let more light in?
|
| Because things flying in is approximately not a problem
| anyway?
|
| Seems perfectly fathomable to me.
|
| (I live in London, occasionally a fly will come in and
| chill out for a bit before sodding off again.. fine? I've
| never had a wasp inside even. Our mosquitoes will
| extremely rarely give you anything nasty. Moths that
| would fly in aren't the fabric-eating kind. Even leaving
| aside the other issues, there's no reason to, it wouldn't
| be worth my time or money to buy them/fit them/have them
| fitted. I've spent longer writing this comment than being
| irritated by anything flying in through my windows.)
| tk75x wrote:
| Why can't you kill wasps?
| OJFord wrote:
| This calls it a 'myth', but really concludes that it's
| hyperbole arbitrarily calling out wasps; they're
| technically a protected species and you could be fined
| but.. almost certainly not going to happen for one or two
| wasps bothering you at a cafe or whatever?
|
| https://medium.com/@sophanemwise/the-wasp-killing-myth-
| in-ge...
| morelisp wrote:
| I had a friend kicked out of a cafe once for killing a
| wasp because they didn't want to deal with the situation
| if the Ordnungsamt was walking by or something.
|
| Wasps are the usual example because it's legal to kill
| flies/mosquitoes and no one wants to kill the other
| protected insects like bumblebees. The wasps in Berlin
| are common and pretty aggressive, and have free rein in
| an awful lot of the chain backeries.
| OJFord wrote:
| Interesting, but are they justified in that fear do you
| know?
|
| What I mean is, if this is a commonly believed
| exaggeration then it could just be that in this case the
| person believing it wasn't the wasp-killer (or would-be-
| killer) but the cafe owner. Has your friend ever actually
| been fined for doing it, or did the cafe owner/manager
| mention having had to deal with it in the past?
|
| Certainly does seem odd that this law would (a) exist;
| and (b) be intended to stop this sort of behaviour; and
| (c) actually be enforced!
| morelisp wrote:
| I doubt anyone has been fined the full value just from
| killing one wasp from some random fine. It is regularly
| enforced against people who try to burn down or otherwise
| remove nests on their property (without engaging a
| professional to try to remove it safely for both
| parties).
|
| I would say mainly it's not enforced because b) has been
| effective - Germans (or Berliners at least) don't kill
| wasps! If doing so became common, it would probably be
| enforced more consistently.
| clort wrote:
| I was at a country cafe in the UK where there were plenty
| of wasps nearby. They had some 'fake nests' hanging up,
| as apparently wasps will swarm and kill intruders, so
| they also don't go near nests that they know are not
| their own.
|
| If it works or not I don't really know but at least I had
| a bowl of ice cream and wasn't especially bothered..
| jbb_hn wrote:
| This sounds like a potentially lucrative business
| opportunity!
| morelisp wrote:
| They are for sale, for cheap, in every drug store.
| minitoar wrote:
| The number of presumably Europeans in here citing screens
| blocking light as a reason for not installing screens
| makes me think maybe those screens are pretty low
| quality?
| morelisp wrote:
| They are low-quality in that they tear pretty easily, you
| need to replace them every 3-4 years or if a bird/cat
| goes nuts on them (5 eur or so per sqm, probably there
| are cheaper brands if you are price-sensitive), but they
| don't block any more light than screens in the US. Less
| than some I've had.
| mncharity wrote:
| Differences in regional naming and screen types are causing
| confusion in nearby comments.
|
| A screen door can be a secondary exterior rigid door with
| metal mesh panels[1], or a hanging fabric mesh door[2]. A
| window screen can be a metal mesh, in a rigid metal frame,
| tightly integrated with a window[3], or a flexible add-
| on[4].
|
| The polyester/fiberglass/etc fabric meshes can be more
| opaque than the metal ones.
|
| [1] https://upload.wikimedia.org/wikipedia/commons/2/22/Scr
| een_d...
| https://www.lowes.com/search?searchTerm=screen+door [2] htt
| ps://www.alibaba.com/trade/search?fsb=y&IndexArea=product..
| . [3] https://www.youtube.com/watch?v=oEdK5h6smTU [4] https
| ://www.alibaba.com/trade/search?fsb=y&IndexArea=product...
| namdnay wrote:
| Depends where in the EU. mosquito nets are quite common
| around the mediterranean, you'll see roller screens on most
| bedrooms around here
| hans1729 wrote:
| Context. Which place (outdoors or indoors) is more attractive
| to the flies/insects? Temperature, Humidity, other attracting
| factors - depending on region and other related params, this
| may change with time of day etc
| knbknb wrote:
| In the NetLogo Models Library there are quite a few similar
| models already, "Moths", "Ants", "Gaslab Maxwells Demon", and
| more variations (adaptive/nonadaptive, single/flocking etc)
|
| http://ccl.northwestern.edu/netlogo/docs/
| qwertox wrote:
| Next step is to set up a grid of ESP32s with MEMS microphones and
| a FFT routine, stream that data to a server and apply some neural
| network to get to know the real amount of flies by tracking them
| individually. Then compare this to the model, and keep improving
| it until it fits.
| mLuby wrote:
| I want a mosquito-killing turret [1] that you could put in your
| bedroom and sleep in peace.
|
| Turns out one exists [2] (in theory--no commercial product a
| decade later), but the one I was thinking of would use
| microphones rather than cameras [3] to detect the bloody
| suckers. Thing is, I can't find any prior research or even
| hints that people have considered this approach. (The closest I
| can find is an app [4] that detects a mosquito from <=10cm
| away.) Here are some of my guesses for why it's not been done:
| A. Maybe it's too difficult to distinguish mosquito buzz/whine
| from background noise, even when filtering in only known
| mosquito frequencies (~400Hz [5]). B. Maybe it's too
| slow to sweep a room with a directional mic that's focused
| enough to detect mosquito sounds? (Say the turret in one
| ceiling corner of a 12x12x8ft room.) C. Maybe
| directional mics don't work well for all sound in their cone
| and so need to be able to "focus" at different distances (by
| dynamically changing the parabolic dish's shape), thereby
| increasing the room sweep time? D. Maybe the parabolic
| dish needs to be so big that it just looks ridiculous?
| E. Maybe all of this is possible but the type of microphone is
| so expensive that it's worth pursuing commercially?
|
| I'm curious what you all think about this. It'd be an
| interesting thing to try making--who hasn't wanted to make a
| death ray while simultaneously furthering the fight against
| humanity's deadliest enemy? [6]
|
| See also this research paper: Detecting Insect Flight Sounds in
| the Field: Implications for Acoustical Counting of Mosquitoes
| [7] (I'm pretty sure this is not directional--they hung an
| attractant 15cm from the mic and I don't see any dish.)
|
| [1]: https://www.youtube.com/watch?v=BKm8FolQ7jw
|
| [2]:
| https://www.ted.com/talks/nathan_myhrvold_could_this_laser_z...
|
| [3]: I don't think cameras are well-suited to detecting
| something so small. The "photonic fence" from the TED talk only
| kinda works by adding a white background behind the bugs so
| it's really easy for the camera to detect them--not that
| practical in a normal room.
|
| [4]: https://www.theguardian.com/science/2018/mar/29/mosquito-
| ear...
|
| [5]: https://www.youtube.com/watch?v=Rcm3rPz_Q94&t=127
|
| [6]: https://mysteriousuniverse.org/2014/08/why-mosquitos-are-
| hum...
|
| [7]:
| https://pdfs.semanticscholar.org/a0bf/4fcd478b6214759046a739...
| mLuby wrote:
| My acoustically-minded friend had the following to say:
|
| > Off the top of my head, I'm guessing the problem has mostly
| to do with background noise, and it only working in
| moderately quiet environments.
|
| > As for locating the source of a sound, there's plenty of
| research that's been done about that. A directional mic doing
| sweeps is probably not your best bet, as it would be slow and
| difficult to cover three dimensions. I would think using an
| array of microphones and using volume and time delay to
| identify location would be much easier. Setting them up in a
| triangular pyramid would, I think, allow you to triangulate a
| sound's position in three dimensions. The problem with this
| two-fold: it's still not super precise, and the mosquito's
| whine is a steady sound, not an impulse where it's easy to
| identify time-delay between locations. You'd probably need to
| have an incredibly high sample rate to identify strong enough
| variations in the sound of a mosquito to effectively use
| time-delay, or place them far enough apart to rely on
| relative volume. Maybe a set of microphones you can set up
| around a room, rather than a single location would work
| better.
|
| > I think this could be solvable by having the laser aim
| towards the sound and do a rapid sweep of the area, rather
| than a precision strike. You could also potentially have the
| device hit targets that will confirm they are being hit when
| you are setting it up so it can calibrate to the environment
| that it's in under regular conditions.
|
| > Another thing to consider is that you would also probably
| need temperature and humidity detection, as both of those can
| affect how sound travels, even over short distances.
|
| I then did more research on the killing part of this--the
| laser. The product I linked above uses two lasers--a low-
| power one to pinpoint the target and to "listen" for its
| exact frequency to rule out benign insects and a high-power
| one to give it instant heatstroke or burn off its wings. But
| with computer-aimed lasers (even non-burning visible green
| lasers), accidental blindness is a real concern especially
| indoors where the beam can unexpectedly reflect off glass or
| other shiny things. So maybe a narrow, powerful non-coherent
| flashlight could act as a spotlight and that'd be good enough
| for a human to still kill it.
| twphysicsphd99 wrote:
| very cool
|
| it would be fun to add static attractors -ie fruit to see how it
| biases the trajectories
| tenderfault wrote:
| > The perfect question for a Sunday afternoon when you have no
| friends
|
| I have one, we both read your post and we just befriended you
| without authorization
| jdowner wrote:
| Maxwell's kinetic theory of flies?
| StavrosK wrote:
| Yes, the path each one takes can very accurately be called a
| "random fly".
| crispyambulance wrote:
| Well, there was at least one startup that addressed the issue of
| flies/mosquitoes indoors. Bzigo. https://bzigo.com/
|
| It's a machine vision system that tracks mosquitoes and aims a
| laser pointer on them (so you can swat them). Don't know if this
| company still exists. It was/is an Israeli start-up and
| apparently not an April Fool's day joke.
|
| It seems to me the best solution is to use screens, but that is
| not as sexy as machine vision.
| jdavis703 wrote:
| > It seems to me the best solution is to use screens, but that
| is not as sexy as machine vision.
|
| There are lots of windows that don't work with screens. For
| example some windows are pushed out as opposed to up, and the
| latching mechanism would conflict with the screen.
| NorwegianDude wrote:
| I was really confused about where this was going when I started
| reading as I thought the title sad files, not flies...
| dmitriid wrote:
| This sounds like the "how many balls can fit in a bus" interview
| question, but somehow more entertaining. Possibly because it
| addresses a real-world situation.
| Tempest1981 wrote:
| Looking forward to this showing up on my next interview...
| m12k wrote:
| In my statistics class we were taught a technique for estimating
| the number of flies in a barn. You capture a fixed size sample of
| flies, e.g. 100, and give them each a little white dot on the
| back, then release them all back in the barn. Leave them to
| mingle for a while, then capture another fixed number of flies,
| e.g. 100. If 5 of them have a white dot on them, then you
| estimate that the 100 flies you captured originally and marked
| make up 5% of the total population, meaning your estimate of the
| total population must be 2000 flies.
| OnlyMortal wrote:
| If they're randomly distributed, that makes sense.
| esaym wrote:
| But how do you catch flies!?!?!
| mkreis wrote:
| Reminds me of how the Allies estimated the production capacity
| of German tanks during WW2: https://medium.com/dataseries/how-
| data-science-gave-the-alli...
| thearn4 wrote:
| Great read!
|
| In comparison, I have to wonder why the "intelligence
| estimates" were so bad/severe over estimates.
| bena wrote:
| My intuition says counter-intelligence. The Allies were
| using intercepted communications, visual confirmation,
| captured sources, etc.
|
| You can send fake reports if you think the other side is
| listening. You can move or mock material if you think the
| other side is watching. You can feed false information if
| you are captured.
| bombcar wrote:
| And this is why you may be better off solving the "serial
| number problem" not by going to entirely random ones but
| instead change to one that implies false data that you
| want the Enemy to find.
| atatatat wrote:
| lol spend more taxes on missiles, pleb.
| pelasaco wrote:
| Thank you! Great read, indeed!
| dotancohen wrote:
| If you're interested, I referenced this and used the
| technique to estimate the quantity of STS SRBs recently:
|
| https://space.stackexchange.com/questions/9261/how-many-
| soli...
|
| Oh, no.... The date on that post is 2015... "recently"... I'm
| old...
| ajnin wrote:
| My intuitive answer to that problem was to say that if we
| assume the captured serial numbers are randomly distributed,
| and the numbering starts at 1, then they will have the same
| average as all the numbers, so the estimate should be the
| average of captured serial numbers times 2. Which gives a
| result close to the formula used in this article, but not the
| same. I'm not sure where is the flaw.
| lostcolony wrote:
| If there are 100 tanks, and you get 1, 2, 5, and 99, your
| method would give 54 tanks ((1 + 2 + 5 + 99)/4 * 2), which
| is obviously wrong.
|
| Your error is in stating "if we assume the captured serial
| numbers are randomly distributed" - you're assuming they're
| -uniformly- distributed. Randomly distributed != uniformly
| distributed.
|
| Their method would give you 125 as a guess. It's including
| the known info (i.e., adding "m") to take into account the
| fact that they're not necessarily evenly distributed.
|
| On that note, if you continued to get tanks at low numbers
| (3, 4, 6, etc), averaging gets -less- accurate, because
| that 99 becomes more and more of an outlier. Their method
| gets MORE accurate, again, because they're taking advantage
| of all data that is known (we know it goes at least to 99),
| and averaging doesn't. The new low numbers we've added mean
| that there are less likely to be many tanks, and the
| formula in the link takes that into account with m/k.
|
| Both methods will be accurate if you have 100% of the data,
| but taking twice the average ignores known data, so the
| sparser the data the less likely it is to be correct.
| saalweachter wrote:
| Hmmm, on the other hand, suppose you first find a tank
| with the serial number 1234.
|
| Then the next 50 tanks you find are all from the range
| [1, 100].
|
| Is it more reasonable to assume that there are around
| 1258 tanks, or that there are probably closer to 100
| tanks, and that first one with the very large serial
| number was not a sequentially numbered tank?
| lostcolony wrote:
| Certainly!
|
| But, from the article's initial proposition - "You do
| know that the Germans have a sequential numbering system
| (1, 2, ..., n)" and in giving historical context "On
| investigation, it became clear that the serial numbers
| were sequential, without gaps."
|
| So, yes, without that being a prior, of course it's more
| likely that that outlier is a strange one off, and you'd
| do better to exclude it from your data set (and/or
| continue to investigate, because it's NOT at all clear
| that the serial numbers are sequential yet).
|
| But, that context and ordering matters. Assume just the
| opposite series of events - you started by finding 50
| tanks with serial numbers [1, 100]. And then three or
| four months go by you didn't get any tank serials sent to
| you. And then you get 1234. 1258 tanks seems really
| reasonable at that point (and, in fact, would fit the
| reality; the Germans were producing ~256 tanks per month
| per the article).
| dilawar wrote:
| paywalled for me.
| rozab wrote:
| Fun idea, but presumably there is a big bias in that some flies
| will be easier to catch for various reasons. I suppose lots of
| population studies on birds, cetaceans or whatever have this
| bias, since you can't just slap a quadrat down and catch
| everything. In fact with these more advanced animals, perhaps
| they're harder to observe a second time since they've learned
| to be wary of humans.
| m12k wrote:
| Right, if you're measuring long enough that predators eating
| some of the flies could be an issue, then you'd want to mark
| them with something only visible under a blacklight, or
| similarly "neutral", so it doesn't introduce a bias.
| Woberto wrote:
| Unless the predator can see in the UV spectrum, like bats
| marcosdumay wrote:
| If predators or age (or moving out or into the measured
| area) are a factor, they are already biased and keeping
| your method neutral will still give you very wrong results.
| mjaniczek wrote:
| I wonder how does that work. Why can you use the 5 flies you
| found to divide the total sample size?
|
| It's kind of giving you an invariant number: * 100 flies -> 5
| flies (5%), 100 / 0,05 = 2000 * 80 flies -> 4 flies (5%), 80 /
| 0,04 (not 0,05) = 2000
|
| But if you used the percent instead (which seems to be what you
| hinted at) then the results vary: * 100 flies -> 5 flies (5%),
| 100 / 0,05 = 2000 * 80 flies -> 4 flies (5%), 80 / 0,05 = 1600
|
| What's the principle, does it have a name I could read more
| about on Mathworld / Wiki?
| m12k wrote:
| You can read more about the technique here:
| https://en.wikipedia.org/wiki/Mark_and_recapture
| ramanan wrote:
| This catch and release pattern is quite common in many wildlife
| surveys.
|
| For example, when estimating tiger populations, instead of
| painting a white dot, rangers set up camera traps to take
| photos. Then they can use stripe patterns as a signature for
| subsequent re-appearances. Quite an interesting intersection
| for image AI with statistical counting methods.
| canadianfella wrote:
| Why would AI be needed?
| MereInterest wrote:
| Are there adjustments that need to be made for non-random
| sampling in that case? I'd imagine that with any territorial
| animal, a stationary camera is most likely to see the same
| animal multiple times.
| ramanan wrote:
| True. I'm no expert in this area, but there are a lot more
| factors too - including territorial range and even
| different camera locations.
| jmiserez wrote:
| My first ever job (in high school) was manually counting
| mosquito larvae in water samples for our local department of
| agriculture. IIRC the aforementioned technique doesn't really
| work for that, instead they collected samples regularly for
| several months at the same spots each year and used that for
| their forecasts.
| Aeolun wrote:
| I found two flies in my house, marked them, then later found
| two more flies without marks. I think this means the population
| of flies in my house is infinite.
| [deleted]
| thaumasiotes wrote:
| You want to consider, based on a distribution of potential
| fly populations, what the odds are that sampling two of them
| will fail to capture two specific ones. For example, you can
| state with certainty that the population is above 3.
|
| Closely related (though not quite the identical problem):
| https://www.johndcook.com/blog/2010/03/30/statistical-
| rule-o...
|
| Applying that directly, we would estimate that the odds of a
| fly in your house being marked are less than 150%, which
| tells us that you should be taking larger samples.
|
| (With only two marked flies, this estimate will always be
| less informative than the fact that you sampled _n_ flies --
| it will tell you that the population is probably greater than
| 2 /3 of _n_ , while the sampling procedure tells you that the
| population is necessarily at least _n_ +2. But as you mark
| more flies, the estimate will be more informative.)
| thaumasiotes wrote:
| Mostly because I thought it was fun, a worked example where
| you mark 100 different flies and then catch 100 unmarked
| flies (releasing each fly individually immediately after
| catching it; maybe you caught the same fly 100 times):
|
| By the rule of three, we estimate the probability that a
| fly in your house is marked at p < 3/100.
|
| We can also model the probability that a fly in your house
| is marked as 100/n, where n is the number of flies in your
| house.
|
| Then 100/n < 3/100 and n > 100*100/3 = 3,333. There are
| probably more than 3333 flies in your house.
| m12k wrote:
| My condolences, that doesn't sound very nice. Unless you're a
| frog, in which case, congratulations!
| vagrantJin wrote:
| Dear m12k,
|
| I have a valid reason to outlaw humour.
|
| Because of you comment 3 things have happened.
|
| 1) I snorted, causing my hot tea to use my nostrils as an
| emergency exit.
|
| 2) My nose became a tea tap.
|
| 3) My screen and keyboard, bless them, are covered with
| tea. My shame in cleaning it up is indescribable.
|
| Bravo.
| paul_manias wrote:
| This reminds me of the time I found two flies in my house
| despite the windows being closed. I vacuumed them up (more
| fun that way) and the next day there were two identical
| looking flies in the house. Did they get out of the vacuum
| cleaner? I vacuumed them up again.
|
| The next day, same story. The flies were now appearing
| throughout the day. They all looked the same. Where the hell
| were they coming from? The windows were still closed. I kept
| vacuuming.
|
| Eventually things were starting to get very irritating. I
| hunted for an entry point for days without finding anything
| and the flies just kept on appearing. I was pretty good at
| vacuuming flies by this point.
|
| By day six I spotted a group of them hanging out near my
| Kentia palm. Aha! A fly had laid eggs in the soil of the
| plant. I had no idea that it was a suitable food source for
| larvae. Needless to say I quickly filled it with gravel and I
| guess that's the story of how I became a qualified Fly
| Detective.
| gnulinux wrote:
| That's scary. I used to be a hardcore insectaphobe, but I
| got over it over the last couple years. Now I don't care
| that much when I see insects in my house. But it is within
| reason! I wouldn't want bugs _reproducing_ in my house,
| that sounds like a slippery slope!
| nyokodo wrote:
| > I wouldn't want bugs reproducing in my house, that
| sounds like a slippery slope!
|
| Don't Google dust mites.
| a11r wrote:
| Or Face Mites.
| scrumbledober wrote:
| This was far more engaging of a story than it deserves to
| be
| Andrew_nenakhov wrote:
| I admire your perception. I'm personally unable to
| distinguish different fly specimens, they all look the same
| to me.
| paul_manias wrote:
| It's only the size and age of them that makes one fly
| distinguishable from another. When they're all being born
| at the same time there's absolutely nothing that makes
| them distinct, and that's your clue that eggs have been
| laid somewhere in the vicinity.
| grahamburger wrote:
| Another fun thing you can do with flies, and also bees and
| wasps, apart from vacuuming them up, is put them on a
| leash. But first you have to freeze them.
|
| Catch one in a cup or plastic bag and stick it in the
| freezer for about 10 minutes. When you take it out it will
| look dead, but it's not (unless you leave it in too long.)
| Being careful not to rip it's wings off, tie a small string
| or fishing line to one of it's legs.
|
| In a few minutes it will thaw and start to walk around, and
| then start to fly. You can now walk it around the park like
| you were carrying a balloon.
| layoutIfNeeded wrote:
| That's animal abuse.
| 411111111111111 wrote:
| *insect abuse
|
| I think repeatidly slapping them with a pretty soft
| plastic attraption until they stop moving is even harsher
| though.
|
| Or slapping them outta the air, trying to electrocute
| them but having too little power on the shitty device so
| only their wings get burned.
|
| Or vacuuming them up
|
| Or flushing them down the drain.
|
| Honestly, whatever people usually do to them it's way way
| crueller
| thaumasiotes wrote:
| > I think repeatedly slapping them with a pretty soft
| plastic contraption until they stop moving is even
| harsher
|
| It's soft to you, not to the fly. You don't slap a fly
| "until it stops moving". When you swat a fly, it
| explodes.
| grahamburger wrote:
| Where would you say it falls on the spectrum of animal
| abuse in relation to going fishing, fly swatting, and
| walking the dog? Those are all activities I'm personally
| ok with.
| madethemcry wrote:
| This reminds me of the flocking boids algorithm by Craig Reynolds
| [0] which is based on three principles: +
| separation: steer to avoid crowding local flockmates +
| alignment: steer towards the average heading of local flockmates
| + cohesion: steer to move towards the average position (center of
| mass) of local flockmates
|
| The algorithm was used to animate the bat swarms in Batman
| Returns (1992) [1].
|
| I love this algorithm, it's easy to develop and experiment with
| and the results feel beautiful & natural. [0]:
| https://www.red3d.com/cwr/boids/ [1]:
| https://en.wikipedia.org/wiki/Boids
| Lio wrote:
| For some reason this reminds me of the Damien Hirst art work A
| Thousand Years[1].
|
| Next step for me would be to turn the attractor into an
| Insectecuter.
|
| 1. https://damienhirst.com/a-thousand-years
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