Why Does One Fly Decide You’re the Main Character?
There are few things in life more capable of turning a perfectly pleasant summer afternoon into an exercise in frustration than a single fly that appears to have developed an unhealthy fascination with our existence. You could be sitting in a garden enjoying a cup of tea, reading a book, or simply admiring the weather after eleven months of rain, when suddenly you hear it. That unmistakable buzz begins somewhere near your left ear before disappearing into thin air, only to reappear seconds later directly in front of your face as though it has arrived specifically to question your life choices.
The strange thing is that most flies don’t behave like this at all. Hundreds of them spend their lives quietly minding their own business by investigating flowers, bins, compost heaps or anything else that seems remotely interesting. Yet every now and again you encounter one that seems to have abandoned all sensible fly behaviour in favour of becoming a tiny airborne menace whose sole ambition is to see how many times a human being can swat thin air before questioning their own coordination.
It certainly feels personal and over days when the temperature is well over 25C, I’m faced with either keeping all windows shut and sweltering or opening one and hoping the diffuser puts the majority off…
You’re Not Being Hunted… You’re Simply Fascinating
Although it may feel as though you’ve become the subject of a very determined aerial assassination attempt, flies are not targeting you out of spite. Their brains are incredibly small and remarkably simple, which means almost everything they do is driven by instinct rather than thought. They are constantly looking for food, moisture, warmth, places to breed and opportunities to reproduce, and unfortunately human beings provide several of those signals all at once.
Every breath you exhale contains carbon dioxide, which many species of flies can detect surprisingly well. You’re simply sitting quietly enjoying the sunshine, but to a fly, you’re a large, warm, breathing biological curiosity that has unexpectedly appeared in the middle of its world. In other words, you’re less of a person and more of an unusually interesting landscape.
Your Face Is Prime Fly Real Estate
If flies are interested in you, why do they always seem determined to investigate your face rather than your shoe? The answer could well be because our face produces a concentrated combination of everything a curious fly is interested in. Every breath releases carbon dioxide directly from our nose and mouth, our eyes provide moisture, our forehead generates warmth, and our skin naturally produces tiny amounts of salt through perspiration. Rather inconveniently, evolution has concentrated all of these attractive features into the exact part of our body you are least happy to have insects exploring.
This explains why flies appear to perform repeated fly-pasts around our head before briefly disappearing and then returning moments later. They’re not trying to annoy, but continually reassessing what they believe might be an interesting source of food, minerals or simply somewhere suitable to land. Unfortunately, what they consider instinctive investigation feels remarkably similar to harassment.
Sometimes the Fly Isn’t Interested in You at All
One of the discoveries made by entomologists is that some male flies behave rather like tiny fighter pilots defending imaginary kingdoms. Instead of searching for food, they establish small territories and aggressively investigate anything entering that airspace. They don’t possess the intelligence to carefully identify every object approaching them, so they simply intercept first and ask questions never.
If you’ve ever experienced a fly repeatedly charging towards your face before pulling away at the last second, there’s a reasonable chance you’ve accidentally wandered into the insect equivalent of restricted winged airspace. The fly isn’t attempting to attack you. It’s attempting to discourage what it assumes is another rival fly from invading its territory, despite the rather obvious difference in size between itself and a fully-grown human – confidence, it would seem, is not directly linked to body size.
Why Does Only One Fly behave Like This?
Perhaps the greatest mystery is why ninety-nine flies can happily ignore your existence while one behaves like a tiny obsessive fan; the answer appears to lie in both species and circumstance. Different flies have different behaviours, nutritional needs and breeding priorities. One may simply be passing through, another may be searching for food elsewhere, while a particularly inquisitive male has decided that your garden chair is located in the middle of his carefully defended kingdom.
There is also a psychological element: us human beings are remarkably efficient at remembering irritation. We don’t recall the hundreds of flies that quietly landed on a fence post twenty metres away because they had the decency to leave us alone. We remember the one that interrupted lunch fourteen times, inspected both ears, landed briefly on our forehead and somehow managed to evade every swat despite appearing to fly with all the grace of a drunk helicopter.
Why Are Flies So Difficult to Swat?
Many people assume flies possess lightning-fast reflexes and it is true that they do have exceptionally rapid visual processing compared with humans. Their compound eyes allow them to detect movement incredibly quickly, meaning your hand often appears to be moving in slow motion from their perspective. By the time you’ve decided to launch what feels like the perfect swat, the fly has already detected the movement, calculated its escape route and departed with an air of complete smugness that should frankly be illegal for an insect weighing less than a grain of rice.
My best weapon of attack is to watch them until they land , then spray them from a distance with kitchen cleaner – my success rate with this is pretty high. – problem sorted until my son gets home from work and opens the front door where they have been lurking with intent…
So Are Flies Actually Annoying on Purpose?
Not really, despite what we may feel; the important thing to remember is that flies aren’t making conscious decisions designed to irritate, but simply following millions of years of evolutionary programming that tells them to investigate warmth, moisture, carbon dioxide and potential territories whenever they encounter them – knowing this however, rarely makes the experience any less irritating.
Frequently Asked Questions
Why do flies keep buzzing around my face?
Your face releases carbon dioxide, warmth, moisture and natural skin oils, all of which attract certain species of flies.
Are flies attacking me?
Almost never. Most flies are investigating, searching for minerals, or defending territory rather than trying to attack humans.
Why does only one fly seem interested in me?
Individual flies behave differently depending on their species, sex and immediate priorities. The particularly annoying one is simply the one you notice most.
Why are flies so hard to catch?
Their compound eyes detect movement far faster than human eyes, allowing them to react before your hand reaches them.
Suggested Images
- A macro photograph of a common housefly cleaning its front legs.
- A humorous image of a fly hovering inches from someone’s face.
- A close-up of a fly’s compound eye.
- A person unsuccessfully trying to swat a fly in a garden.
- An infographic showing why flies are attracted to carbon dioxide, heat and sweat.
Suggested Internal Links
- Why Do Wasps Keep Returning to the Same Spot?
- Why Do Mosquitoes Bite Some People More Than Others?
- Why Do Bees Never Seem Interested in Your Food?
- Why Are Midges So Bad in the UK?
Suggested External References
- Royal Entomological Society
- Natural History Museum
- British Pest Control Association
