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Can a Fly Scream?

23 Jan 2020
Fly Fear House Fly

The scream was high-pitched – at the very upper end of hearing – but incessant and coming from the kitchen window. It took a while to locate the exact source, which turned out to be a housefly being methodically wrapped by a spider in the corner of the window.

The fly was screaming for all its worth. But does a fly have the sort of emotions that would make it scream with fear? There’s a prior question: how does it scream?

A fly’s buzz comes from its wings. However, this one’s were firmly bound. A fly’s mouthparts aren’t the right shape to make sounds and they don't breath through their mouths anyway. They do that through tiny holes along their body called spiracles. So where was the noise coming from?

Was it afraid? Are flies capable of emotions like fear or happiness? Until fairly recently, the stock answer has been a categoric ‘no’. Recent research suggests we’ve been too hasty to dismiss insect emotions.

Back in 1872 it was a question that fascinated Charles Darwin. In a lesser-known book The Expression of Emotions in Man and Animals, he wrote that insects “express anger, terror, jealousy and love.” Current science at the time wasn’t up to proving it, but just recently biologist David Anderson at the Howard Hughes Medical Institute devised a complex apparatus to study the reaction of flies to danger using a looming shadow.

There reactions were much like ours: first they froze, then they jumped, then they flew around in agitation and refused to eat afterwards. They were, it seems, emotionally stressed.

A similar experiment printed in Current Biology in 2015 concluded: “Our results suggest that flies' responses to repetitive visual threat stimuli express an internal state … analogous to fear in mammals.”

More remarkable than the screaming was the apparent distress of another fly at window pane. It approached the murder scene, skittered away, approached from another angle, rubbing it’s front legs together in agitation. Then it zoomed up and away, only to return and buzz around the spider, dangerously near the web that had ensnared the first fly, displaying all the symptoms we associate with extreme concern.

So how does a fearful fly scream? The jury is still out on that.

About the Author:


Dr Don Pinnock is an investigative journalist and photographer who, some time back, realised he knew little about the natural world. So he set out to discover it. This took him to five continents – including Antarctica – and resulted in five books on natural history and hundreds of articles. The Last Elephants, published this year with Colin Bell, is his 18th book.

His other books include:

Gang Town, which won the City Press Tafelberg Non-Fiction award,
Writing Left, a biography of the journalist Ruth First.
Voices of liberation
The Brotherhoods,
Gangs, Rituals & Rites of passage
Rainmaker, a novel shortlisted for the 2009 European Union Literary Award.
Natural Selections,
African Journeys,
Just add dust,
Loveletters to Africa,
Blue Ice: Travels in Antarctica,
The Woman who Lived in a Tree and Other Perfect Strangers.
Wild as it Gets,
He has degrees in criminology, political science and African history and is a former editor of Getaway travel magazine.

He was one of the primary drafters of the White Paper that became the Child Justice Act, a trustee of the Chrysalis Academy for high-risk youths, a board member of Wilderness Foundation Africa, a member of the Conservation Action Trust and was the facilitator of the Western Cape Government’s gang strategy roadmap.

His day job is as environmental investigative journalist.