Here’s How That Annoying Fly Dodges Your Swatter | Deep Look

A fly has a pair of tiny, dumbbell-shaped limbs called halteres that were once a second pair of wings. They wield them to make razor-sharp turns and land out of reach on your ceiling. But don't despair – there *is* a trick to smacking these infuriating insects.


DEEP LOOK is a ultra-HD (4K) short video series created by KQED San Francisco and presented by PBS Digital Studios. See the unseen at the very edge of our visible world. Explore big scientific mysteries by going incredibly small.

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Flies are formidable opponents, with an arsenal of tools they carry all over their bodies. For starters, their hair and antennae help a fly sense us as we walk up to them. And a fly’s eyes and tiny brain process information 10 times faster than human eyes and brains.

“Compared to flies, humans are slow and sluggish creatures,” said Sanjay Sane, who researches flies at the National Centre for Biological Sciences at the Tata Institute of Fundamental Research in Bangalore, India.

Once the fly escapes your swatter and is in the air, it’s in its element and your job is even tougher. Seen up close and slowed down, a fly’s aerobatics are impressive: It makes razor-sharp turns with ease and at great speed.

What makes this possible is a pair of modified wings called halteres, a Greek word for dumbbell, which describes their shape. All of the 200,000 species of flies that scientists have described have a pair of halteres and a pair of wings. (That includes mosquitoes, which, wouldn’t you know it, are flies too). Most other insects – bees, butterflies, dragonflies – have four wings and no halteres.

--- How do flies’ halteres work?

As a fly turns, its halteres sense the rotation. In a split second, neurons at the base of the halteres send information to the fly’s muscles to steer its wings and keep its head steady.

“Houseflies flap their wings about 200 times per second, which means they really only have five milliseconds to figure out what the next wingbeat is going to be like. And if you’re using vision that takes too long to do,” said Jessica Fox, who studies flies at Case Western Reserve University, in Ohio. “They really need a mechanical receptor in order to be able to sense their body rotations and correct them on the timescale that they need.”

--- How do flies land and stay on the ceiling?

Their halteres allow them to rotate quickly to land on the ceiling. Once they’re there, they hang upside down with tiny hooks and sticky pads on their feet. The pads, called pulvilli, have microscopic hairs that excrete a liquid that sticks to the surface.

--- How do I swat a fly?
“Flies process information about moving objects but they cannot process static objects, Sane explained. “Thus, the best way to approach a fly is in small, quasi-static steps such that they do not see you as a moving object.”

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🏆Congratulations🏆 to the these 5 fans on our Community Tab for identifying the tiny limbs beneath a fly's wings - halteres:

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[venusclarkangelo]

That is why i cant kill this piece of insect because all the parts of its body is a freaking wind sensor. With 360 vision

[AndrewCamarata]

Kinda wish I could Unwatch the fly pooping

[CRG]

When a fly loses its wings, it's not a fly anymore, its a walk

[MemeDogelol]

I’ve never felt the same level of badassery compared to catching a fly outta mid air.

[duchi]

They're still not fast enough to dodge my mom's flip flops

[antbereishit]

Fly: • Literally super creature. •

Window: I'm about to end this mans whole career.

[JoeyIndolos]

I read the autobiography of this American officer who was a POW in the Korean war. In between the hard labor and torture were hours of boredom, and one thing he became very good at was killing flies. His main advice was to wait for when they would clean their folded wings with their hind legs (like at the 0:41 point in this video). They could still fly off in a split second, but because they had to bring their legs down first, it took a bit longer than from any other starting position, and gave you the most chances of killing it.

[pi.actual]

I purchased a device called the Bug-A-Salt. It's basically an air gun that discharges a shot of table salt. A direct hit will literally blow the wings off a fly however it states in prominent letters "DO NOT SHOOT IN FACE OR EYES" and I find this very difficult to comply with since about 30% of a fly is eyes.

[obliterator]

"The fly's brain processes information 10 times faster than ours" Well now I can take pride in myself whenever someone says I have fly sized brain.

[rainnyyolk]

"Ma'am here's your salad"
"Leave it on the table"
"But a fly may land on it"
"Exactly!".

[damonr]

When a fly lands on a flat surface, clap your hands right above it.

[worldaviationk]

I thought I had a fly floating in my cup of tea for the morning for when i woke up. I almost drank it as my blurry eyes were opening i saw a blob then about to drink and stopped myself, stuck my fingers in while eyes still closed a bit just thinking it was some chocolate left on the cup from the day before and i felt a squish and a sting and threw it away. I then realised it was a wasp floating. Good job I didn't drink before opening my eyes.

[danieltdp]

What amazes me even more is seeing my dog killing flies with a controlled bite. It grabs the fly then spit it out dead but not dismembered

[karepmuu]

Even flies learn to “wash” their hand before eating meal

[DriesduPreez]

2:08 I really appreciate the sound design here, where they have the drum sounds synched with the halteres

[smileyfawler]

Only makes me more proud of how my cat Garfield catches these in his mouth mid air with seemingly zero effort.

[onemoremisfit]

A long time ago I was trying to fall asleep when a large loud fly was buzzing back and forth in the room, keeping me awake. I got up and started chasing it with a swatter, but it would not land. My dog seeing the action got up and started chasing the fly with me, and I got mad at her because she was getting in my way. Then the fly took a low swoop past the dog, she snapped her jaws, and the fly was gone. Good dog.

[sarahthegreat]

Fly: imma act like I didn't see that

[miepmaster]

Here is a pro tip: clap your hands roughly 5cm above them, if you guess their speed correctly you will swat them every time

[randmayfield]

The color of your fly swatter matters also. I noticed how with some colors like yellow and red, even in setting up for the swat, the fly could sense the swatter earlier and therefore avoid it easier. Green, blue, and beige all worked better.