ELi5 Why can flys see you coming a mile off when you try to swat them…but they can never seem to find their way back out of an open door?
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I want to add that flies often don’t want to leave. I doors usually way better temperature, humidity, etc. and there’s tons of food there. That can be why they bee-line to get inside (no pun intended) and don’t leave.
Because you fell into the trap of thinking like a human. Flys don’t have eyes like we do. They don’t depend on vision like we do. They are sensitive to changes in micro air currents and fly according to what they feel. The distance between their wings and their brains is shorter than the distance between our hands and our brains and therefore they are able to react more quickly than us. So they can outmaneuver you in air to air combat but a gusty door is an impenetrable wall to them.
they can detect the changes in air movement as you swing at them. They can react easily around swatting because they can ride the airflow around as what ever is swatting them swings.
Fly eyes are setup very differently than mammals. You have 2 eyes that are great at color and detail. Flys have like 60 eye that really see changes in movement. If you think of you eye like a mirror and a flys eye like a disco ball. In the single mirror you can see fine details. The disco ball not so much, but you can catch movement from many more directions.
Also the fly has a « brain » of a well house fly
They don’t see it coming. They *feel* it coming. At that scale they are able to react in a time frame you can’t even comprehend.
A small pressure wave in front of your hand wiggles a hair ever so slightly and they are gone. Meanwhile, the sound of your swat hasn’t even had time to reach your ears yet let alone trigger a complex chain of chemical reactions that culminate in your consciousness reaction to everything that happened.
Step back and think about it. The fly could make 1000 decisions and change course 1000 times before you could send a signal across your nervous system to move your hand. Just because of how much farther the signal would have to travel.
Open your front door just a crack, and you can feel air moving between the room you’re in and the outdoors. An open door has no discernible wind to us, but to a tiny fly, it might just be too breezy. Like trying to paddle a boat against the tide.
It works for me 9/10 times, but here it is
Flies and all insects follow light, turn off all lights and they’ll follow light Comin from door.
If you want to remove fly’s from a room try making the room dark as possible (not always possible I know) then create some light by uncovering an open door or window. The fly’s will almost always fly towards the light and exit the room.
Flies did not evolve in an environment that had doors and windows and buildings with internal light sources. In nature, if a fly is in, say, a cave, and goes towards a source of light, most of the time it’ll end up flying out of the mouth of the cave. This doesn’t work for human-created environments like houses and apartments.
On the other hand, the environment in which flies evolved absolutely had larger predators who were trying to harm them by grabbing or swatting them with a limb. They evolved a nervous system that uses their highly effective compound eyes, which aren’t very useful for resolving details but are great at detecting motion nearby, to send a signal to their wings to fly away rapidly.
Their concept of time is also different than ours. So fast things are normal to them and slow things might as well be similar to the growing of a plant to us. You move slow to them, they can’t perceive it.
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