Are houseflies a filthy nuisance or unsung heroes of nature?

To most people, houseflies are filthy, disease-carrying nuisances best wiped off the face of the earth. But are they truly nothing more than pests? Entomologists and environmentalists beg to differ.

Scientifically known as Musca domestica, houseflies are scavengers that play a crucial role in the ecosystem. They consume decaying matter such as carcasses and faeces, helping break down and recycle organic material and nutrients back into the environment.

“Without flies, humanity would be swimming in filth,” says Augustine Ruto, a hotelier in Garissa. “They’re essential decomposers.”

Ruto also notes that fly maggots, rich in protein, are used as fish bait and animal feed. In forensic science, the number of maggots found on corpses can help determine the time of death.

In an increasingly fragmented world with deforestation and habitat loss, flies also visit flowers and contribute to pollination, supporting plant reproduction and food supply chains.

Flies play additional roles in farming. Hoverfly maggots feed on aphids, reducing the need for chemical pesticides, while parasitic flies attack crop-damaging pests such as caterpillars and beetle grubs.

“Fewer flies would disrupt food chains and depopulate species that depend on them,” explains Reuben Alembi, an environmentalist in Mororo, Tana River County. “Predators would struggle to find food, causing a wider ecological imbalance.”

Ruto adds that flies have an innate ability to detect and destroy pathogens, which could be key in future immunity research. Research at Stanford University even highlights the potential of a fly's immune system to inform human health solutions.

A Double-Edged Sword

Despite their ecological value, flies have a dark side. They are vectors of disease, mechanically transmitting around 65 preventable but life-threatening illnesses to humans and animals. These include cholera, dysentery, typhoid, salmonella, anthrax, and tuberculosis.

“Of course, treating these diseases comes at a cost,” Ruto notes.

Flies contaminate uncovered food and open wounds by regurgitating pathogens through their sharp, piercing mouthparts. They are drawn to the dead cells and odour of wounds, which is why they lay eggs and feed on infected areas if left uncleaned.

“They hover around humans for sweat, oil, sugar, and salt—all nutrients they love sipping,” says Alembi. “They even inject anticoagulant saliva into the skin to aid feeding.”

Yet Alembi insists that blaming flies for disease overlooks the real issue: poor hygiene.

“People don't want to coexist with flies, yet they fail to maintain basic hygiene. That’s the real problem,” he argues.

Prof. Leo Ogalo, Dean of Agribusiness Technology and Microbiology at Great Lakes University in Kisumu, points out the irony: “Flies are born, bred, and thrive in filth, yet they clean themselves constantly.”

Houseflies have a roughly 28-day life cycle and breed in garbage and feces. Still, they regularly groom by rubbing their front legs together, helping to remove dirt, moisture, and pollen from their hairy bodies.

“This grooming behavior is essential,” Prof. Ogalo explains. “It helps clean their sensory organs, improves flight, and aids in finding food and mates.”

Flies even release pheromones through this process, helping them communicate, mark territory, and attract partners.

Can We Coexist?

Despite their ecological and scientific benefits, most people still find flies intolerable. Amos Ogosiah voices a common sentiment: “Any place full of flies signals filth. They're uninvited guests.”

Flies are fast and agile, making them hard to swat. Alembi suggests peaceful coexistence through non-toxic solutions.

“Instead of harsh pesticides harmful to children, pets, and the environment, try natural repellents,” he advises. “Scents like lavender, eucalyptus, or plants like basil and Venus fly traps repel flies while beautifying your space.”

Entomologists explain that flies are attracted to human scents like sweat, lactic acid, and carbon dioxide.

Ruto concludes, “With both advantages and drawbacks, extermination isn't the answer. Let’s manage them wisely.”

In the end, the humble housefly—reviled by many—might just be one of nature's most misunderstood creatures.