Why houseflies like humans

Lubna Abdel-Aziz
Tuesday 21 Jun 2022


Now that summer is officially started (21 June) in the northern hemisphere, we are ready to enjoy the season of the sun. It has been a wicked winter and we are yearning for the outdoors, basking in the sunshine, surfing, swimming, playing ball, and all the rest of the fun in the sun.

Unfortunately, we humans are not alone. All sorts of animals and insects are done with hibernation and more than willing to share in summer’s pleasures.

Here you are. It is a beautiful summer afternoon, you are dressed or undressed for the warm weather, happily breathing in your natural Vitamin D, with a cool drink in your hand, perhaps contemplating a barbecue for dinner “al fresco”, when they start coming one by one.

You knew they were coming. You are well armed with swatter in hand ready to do battle with that pesky little nuisance, the imperishable fly. There are at least 240,000 identified species of flies, among them the common housefly, our summer nemesis. It is bothersome, troublesome and irksome, but this persistent, insistent nuisance seems to know exactly what it is capable of. It will feast with you, accompany you and will enjoy the summer by your side. No matter how often, how high, how wide you swing your swatter, the fly will get its share of summer joy.

If you have your food all covered up and well protected, you will become the source of its food.

What do these little scavengers want from humans? Do they not feed on dead carcasses, rotten fruit, vegetables, organic animal, or human fecal matter, any or all kinds of waste — what do they want with us?

Is it their job to annoy us all summer? It seems so. We forget that our skin sweats and that sweat contains protein, carbohydrates, salt and sugar, therefore if there is no dead carcass a live human will do. We also exhale carbon dioxide and they like the taste. Very often they aim at your mouth while you are talking. They are drawn to strong smells; our colognes and perfumes attract them so do people with type O blood. What is a human to do? Just keep up the fight.

In a study that spanned six years, thousands of experiments, Caltech scientists discovered fruit flies are attracted to CO2, a gas associated with their favourite foods, as well as some of our beverages, which overturned an earlier consensus that flies avoided CO2.

Forget the BBQ, just hold a can of beer, glass of wine, or just plain soda, they wish to share it with you. You swing and you sway your swatter, but the buzzing noise grows louder.

Biologist David Andersen warns: “Flies and bees can get angry.” Every time you swat a fly, it seems to come back more aggressively and persistently. Andersen identified a brain chemical involved in promoting anger. Do not anger flies.

You are a tasty meal, so is what you eat or drink. Swat, shoo, and yell as much as you want, flies are unphased by humans. We are no threat to them, neither are our weapons of destruction.

They have been here for millions of years and will likely outlive humans.

They may have two eyes but they equal 1,000 eyes and can fly away from danger within 100 milleseconds due to their complex, compound eyes. Their eyes allow them to see all around them without having any blind spots.

Always associated with dirt, yet according to Maggie Hardy of Queensland University, they are very fastidious about their cleanliness. That is of no help. Throw away food if a fly sits on it for long, the higher the chance of transmitting harmful bacteria.

They take risks in order to target their next meal — and you may be it.

These little carnivores are dangerous as they carry pathogenic organisms which can cause various diseases, so keep swatting and find ways to protect yourself and the food you eat.

It has always been a mystery how they can make a huge animal carcass disappear in no time. How do they eat without teeth? Their mouths are like sponges or straws. They soak up whatever they eat, transforming solids into liquids. One can say they drink their food.

Anything appealing about them so far?

Well they are essential to our eco-system. Without them we would have rubbish and dead carcasses everywhere.

Scientists inform us that the food we eat was probably pollinated by flies. Not just bees and butterflies pollinate but flies do a better job. Recent research at the University of New England shows that the common blow fly can carry more pollen stuck to its body than a honeybee.

Flies also pollinate hops in beer, apple cider, and grapes in wine. Any desire to say cheers to the fly? No.

It is baffling that this ugly insect that we keep shoo-ing away throughout the summer was an inspiration to many an artist. British poet William Blake wrote a touching poem about “The Fly”, so did Walter de la Mare and Emily Dickinson, among others.

Most famous is the work of Nobel Laureate William Golding Lord of the Flies, but the flies in his famous novels were boys. Why refer to them as “flies”?

Songs, paintings, plays, and movies include flies.

So, you might as well have your BBQ, but do keep your fly swatter handy. We need protection from our summer companions.


“Am not I a fly like thee/ Or art thou a man like me?”

 William Blake (1757-1827)

A version of this article appears in print in the 23 June, 2022 edition of Al-Ahram Weekly.

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