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Why is it so hard to swat a fly?

bbc.co.uk

11–20 of 80 posts

Re: Why is it so hard to swat a fly?

#11
I have perfected this. I can even stop them mid-flight.

Spray at it with any liquid (e.g. water, household cleaner). It may take a couple of squirts but it's easy as it doesn't need to be exact. The fly will fall to the ground where you can just squash it with a tissue.

Re: Why is it so hard to swat a fly?

#12
As someone who works in visual neuroscience, this article's a tough read. Lots of statements that are semi-accurate at best.

1) Eyes don't work like cameras; there's no real "exposure" phase as such (even though there's lots of thresholds). So it's misleading to talk about discrete images that we sample at some fixed frequency. Instead, it's much more helpful to think of photoreceptors and subsequent processing stages as continuous band-pass filters. At some point, high frequencies are simply cut off because the electro-chemistry of the cell can't keep up. For us, that cut-off comes earlier than it does for invertebrates.

2) There's no mechanical interaction between light and photoreceptor. Instead, the transduction cascade of the dipteran eye seems to encompass a mechanical (as opposed to biochemical) step.

3) It's pure conjecture to talk about a fly's slowed down "perception" of the world. The reason why they take off before you get to them is much simpler -- there's a highly optimized reflex that connects eye and flight muscles via the giant fiber (a particularly rapid nerve). We have similar responses, like eye lid closing etc. Additionally, their photoreceptors are sensitive and fast. But there's zero evidence that flies have any sense of continuous time that could be faster than ours.

Ah, well. The perils of science journalism.

Re: Why is it so hard to swat a fly?

#13
post #5

If you want to catch a stationary fly, it's pretty easy to do so with your bare hands. The key thing to know is that they jump backward before taking flight. Aim for a spot about 1-2" behind the fly, and about 1-2" above the fly. Try to catch it there , and your success percentage will be high.

What... is the air-speed velocity of an unladen fly?

Re: Why is it so hard to swat a fly?

#14
post #12

As someone who works in visual neuroscience, this article's a tough read. Lots of statements that are semi-accurate at best. 1) Eyes don't work like cameras; there's no real "exposure" phase as such (even though there's lots of thresholds). So it's misleading to talk about discrete images that we sample at some fixed frequency. Instead, it's much more helpful to think of photoreceptors and subsequent processing stage…

Just to add the distance from a fly's eyes to it's flight muscles is very short which inherently reduces reflex time.

They might not view time faster, but they view and react to events much closer to the present.

Re: Why is it so hard to swat a fly?

#15
Differences in visual flicker-fusion rate between species is interesting. But I think it's a bit presumptuous to claim that time drags by 4x more slowly in a fly's reality, and that's why it can usually escape a giant hand falling from the sky. The fly escapes because it's quicker than you. It would probably be just fine if could detect motion at 60 Hz.

Re: Why is it so hard to swat a fly?

#16

Three techniques: 1. Move your open hand towards the fly very slowly until you are 5cm (2 in) away then slap. 2. Move both hands slowly towards the fly and "clap" to catch it. 3. Blow gently downwards onto the fly, then slowly increase the force of the blowing. You might then be able to pin its wing to the surface. Yes, I have a lot of time on my hands.

>Yes, I have a lot of time on my hands.

Also a lot of fly goo.

Re: Why is it so hard to swat a fly?

#17
post #4

The article doesn't mention this but as I understand flies can only see motion. So when you move very slow you can catch them. It doesn't mean that they only see moving objects by the way. In flight they see because everything is moving around them.

I thought that most (all?) eyes only see motion, just as you do not feel the weight of your clothes anymore (or the presence/absense of your wallet in your back pocket) after a while. But reading up on microsaccades[1] - tiny involuntary eye movements which I thought fixed that in mammals - that does not seem to be the current understanding anymore.

1: https://en.wikipedia.org/wiki/Microsaccade

Re: Why is it so hard to swat a fly?

#18
post #10

Where’s the video of the killer fly catching a fruit fly? I want to see that .

Also, what is the scientific name of the killer fly? There is no such article on wikipedia.

And some more references on how compount eyes see mechanically, as opposed to chemically, would be interesting.

Re: Why is it so hard to swat a fly?

#19
post #12

As someone who works in visual neuroscience, this article's a tough read. Lots of statements that are semi-accurate at best. 1) Eyes don't work like cameras; there's no real "exposure" phase as such (even though there's lots of thresholds). So it's misleading to talk about discrete images that we sample at some fixed frequency. Instead, it's much more helpful to think of photoreceptors and subsequent processing stage…

Thanks for the informed opinion. I know way less about animal vision than machine vision but the statement that eyes have a "frame rate" and "send images to the brain a fixed number of times a second" smelled really bad.

A maybe-dumb question about point (3) - I've noticed that when I get a blink/flinch response from something (usually some sand or a bug hitting my face when I'm on the bike), it feels like I blink just a split second before the thing hit me. Given that I'm unlikely to have any kind of precognition, do you think this might be related to the blink reflex being 'hard wired' and so my brain gets the "hey, a thing hit your face" signal after the "hey, your eyes just closed" signal? (Alternately, I read something once about our perception of audio being delayed by ~100ms so that it synchs up with our perception of vision, despite our visual processing being slower than audio - maybe the signal that caused the flinch gets 'buffered'?)

Re: Why is it so hard to swat a fly?

#20
post #5

If you want to catch a stationary fly, it's pretty easy to do so with your bare hands. The key thing to know is that they jump backward before taking flight. Aim for a spot about 1-2" behind the fly, and about 1-2" above the fly. Try to catch it there , and your success percentage will be high.

The perspective of cathing a fly that walked on crap five minutes ago disgusts me. I know they cleanse their paws more often than I do mine, but faugh.
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