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The ingenious flight of flies — nature’s tiny aeronauts mastering survival and escape

The ingenious flight of flies — nature’s tiny aeronauts mastering survival and escape
Don Pinnock
By Don Pinnock
4 Feb 2025
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As creatures that own the air, these annoying house pests — or guests — simply have no equal.

Life on Earth began by learning to swim then crawl, then run and finally – in a burst of innovation – to fly. The first fliers were probably beetles, followed by pterodactyls, then by the feathered dinosaurs we call birds, then bats and, finally, the most accomplished of all: flies. Yep, flies, Musca domestica.

Their habits may not please us, but their aerial abilities are spectacular. As to why, let’s begin with the speed of their perception. If it’s night time, the fly cleaning its front legs and regurgitating a bit of urk on your kitchen counter under the fluorescent light is not seeing what we’re seeing.

Alternating current arrives at 60 cycles a second, but our eyes can only detect events with intervals of 1/20 of a second, so the light appears continuous. The fly’s nervous system is so fast it can detect changes 330 times a second and can see ultraviolet light. So, for it, the light is going on and off like a slow strobe. In the lit moments we seem to the fly to be hardly moving at all.

It would be happy to hang out watching the scene through its 4,000 crystalline eyes unless you decide to swat it. Its perception is sharp but not long range, and it would be only vaguely aware of you moving towards the counter, raising your hand and beginning what in your terms is a lightning strike.

Acquired technique


The fly clearly sees your hand descending through the slowly strobing light and begins to calculate its reaction, honed by about 250 million years of acquired technique. Its brain works out the trigonometry of your hand to ensure the best escape trajectory. Muscles on the outside of its chest start pulling in the material that forms the attachment to its wings, clicking the wings inward, ready for movement and pumping blasts of oxygen through silvery air hoses to where it’s needed as jet fuel.

At this stage your hand is less than 5cm away, but there’s time enough for the fly to send a message to get the starter muscles ready and pull the wings downwards, ready for take-off. Then it crouches slightly and pushes straight up, catapulting itself into the air.

For a microsecond it hovers there, then pulls in its undercarriage, turns sideways and accelerates, its wings beating at 200 beats a second, its body moving at 40km/h, leaving your hand to smack an empty counter. You have almost no chance of hitting a fly that way.

Its speed does pose a problem it needs to contend with, however. Because of its perceptual rate, the fly under a neon light is moving through times of absolute darkness between strobes. Navigating in the dark is not easy. How to stay on course?

The answer is the secret to its brilliant flying ability: it has two gyrocompasses, called halteres, sticking out from behind its wings. If it yaws, pitches or rolls, they correct its trajectory, keeping it on perfect course by sending path corrections to its wings.

Aerial acrobatics


A safe spot, far from irritating human hands, is likely to be the ceiling. But flies can’t fly upside down because, like aeroplanes, they lose lift bottom side up. So how to accomplish an upside down landing? It’s solution is a remarkable feat of aerial acrobatics.

It slows slightly, flying just below the surface and raises its two front legs above its head. As these contact the ceiling, it flips its body over and lands upside down. There, because flies are largely diurnal, it will probably spend the night.

Here are a few other facts as you ponder the fly you just missed swatting. They taste with their feet, which is why they zigzag over your sandwich to find the best bit, can fly at about 40km/h and have nearly 365-degree vision. They have associated with all species of hominin throughout time, including our own Homo sapiens.

There’s a definite downside to flies. They walk on things with sticky feet that you would find totally disgusting and then on you. A single housefly is estimated to carry nearly two million bacteria. And flies exist in vast numbers.

Their ability to thrive in various climates and adapt to urban environments has contributed to their global distribution – there are more than 120,000 species. They’re one of the most adaptable and ubiquitous insects on the planet.

Extremely high in protein


Although they’re often viewed as pests, house flies have a role in the ecosystem by helping decompose organic matter and being food for predators like birds, spiders and other insects. Their larvae are extremely high in protein and are increasingly being used as pet and even human food.

Eating that which decays, they are also excellent at cleaning wounds. Genghis Khan’s armies travelled with cartloads of flies, using their larvae to disinfect their soldier’s battle lacerations.

An American Civil War medical officer, Dr JF Zacharais, noted that “maggots… in a single day would clean a wound much better than any agents we had at our command”. They secrete allantoin, which stimulates healing and occurs naturally in comfrey, a common skin treatment, as well as ammonia, which acts as an antiseptic.

A speedy life is not good for longevity, however. An average fly’s lifespan is seldom longer than a month. Without food, a mere two days. Swat with respect.

Sources


The primary source is to watch flies with interest. They have fascinated both scientists and popular writers for good reason.

High on the list of popular works are The Story of the Fly and How it Could Save the World by Jason Drew and Justine Joseph, and The Secret Life of Flies by Erica McMaster. A useful source is a quirky book called The Secret House: The Hidden World of Your Home by David Bodanis, which, though not about flies, has some great information about them and everything else with which we share our homes.

The entire genome of the fruit fly was sequenced in 2000, making it the first insect to be so honoured. This milestone has opened new avenues for research in evolutionary biology and genomics. About 75% of human disease-related genes have counterparts in fruit flies. This genetic similarity allows researchers to study diseases such as cancer, diabetes and neurodegenerative disorders using fruit flies as model organisms. DM

This story first appeared in our weekly Daily Maverick 168 newspaper, which is available countrywide for R35.

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