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How many flies are in my apartment?

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Re: How many flies are in my apartment?

#101

Post by paul_manias »

Aeolun wrote: post #76
m12k wrote: post #40

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 orig…

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.

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.

Re: How many flies are in my apartment?

#102

Post by m12k »

mjaniczek wrote: post #98
m12k wrote: post #40

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 orig…

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%),…

You can read more about the technique here: https://en.wikipedia.org/wiki/Mark_and_recapture

Re: How many flies are in my apartment?

#103

Post by Tempest1981 »

yarcob wrote: post #29
morelisp wrote: post #22

Earlier quoted context omitted.

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.

Maybe because screens make the appartment darker?

Fortunately, the sun is getting brighter

Re: How many flies are in my apartment?

#104

Post by morelisp »

rossdavidh wrote: post #97
mig39 wrote: post #89

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.

"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.

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.

Re: How many flies are in my apartment?

#106

Post by scrumbledober »

paul_manias wrote: post #101
Aeolun wrote: post #76

Earlier quoted context omitted.

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.

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 we…

This was far more engaging of a story than it deserves to be

Re: How many flies are in my apartment?

#107

Post by lolc »

rossdavidh wrote: post #95
lolc wrote: post #34

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.

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.

Sure, the inverse square law applies to smells as well.

Re: How many flies are in my apartment?

#108

Post by clort »

morelisp wrote: post #77
OJFord wrote: post #64

Earlier quoted context omitted.

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...

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.

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..

Re: How many flies are in my apartment?

#109

Post by dilawar »

mkreis wrote: post #46
m12k wrote: post #40

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 orig…

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...

paywalled for me.

Re: How many flies are in my apartment?

#110

Post by lolc »

pelasaco wrote: post #90
lolc wrote: post #34

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.

an interesting research in this area https://journals.plos.org/plosone/article?id=10.1371/journal...

Thanks, that was an interesting read on the topic!
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