Why are there so many flies around?

Buzzzzzzzzz buzz buzz buzzzzz buzzz buzzz.

There’s a good chance that you’re hearing this sound as you read this – UK homes are being overrun with a plague of houseflies this summer.

The nation is about to enter its fifth heatwave this year, raising fears of these droning insects swarming us.

They have, among other places, crawled on people sleeping in Leamington Spa, swarmed beaches in Scotland and laid siege to Congleton West Heath for so long that people are petitioning the government to help.

This shouldn’t be too surprising; for each person on Earth, there are 17million flies.

But flies are also, well, dropping like flies – insect populations are ‘dramatically’ dropping around the world amid climate change.

So, why are there so many flies at the moment?

Experts Metro spoke to aren’t sure if there are more flies inside our homes because their numbers have increased or are just more noticeable.

Andrew Whittington, of the insect identification service Fly Evidence, says that it being hot is a big reason why either way.

Houseflies are cold-blooded critters, meaning that their body temperatures fluctuate with the air around them.

‘Fly populations rise and fall with temperature changes, increasing suddenly and sometimes alarmingly with increasing heat in summer,’ Whittington says.

‘As with most insects, peak populations are reached in summer months, and there are some years worse affected than others, such as those with lower rainfall or less wind.’

When it’s warm, a housefly’s metabolic rate goes into overdrive, making them eat, mate and lay eggs even faster.

Balmy weather also leads to more fruit flies, as they thrive in hot, humid spots.

But why, of all places, are there flies in my living room?

Many flies have adapted to live alongside humans to have better lives, a relationship experts call synanthropic.

And humans are making it all too easy for them, the Royal Entomological Society, a charity which brings insect experts together, says.

‘Warm weather means we keep windows and doors open more, naturally increasing the chances of insects finding their way indoors,’ it says.

Houseflies don’t just mindlessly roam in circles around your head when they enter your home. They’re looking for moist, decomposing matter to feast on and lay 500 eggs over 30 days.

In other words, a compost caddy or open bin is an all-you-can-eat buffet – as well as a nursery for them to have maggots on.

‘Economy balancing moves by councils to empty wheelie-bins less frequently do not help the situation and the recent demand to use food caddies is a disaster,’ adds Whittington.

‘Few people rinse their bins and recycling boxes, leaving a slurry behind that is highly attractive to house flies.’

Rural areas that are near farms, rubbish dumps and poultry houses may also face housefly invasions.

Houseflies, bluebottles and greenbottles are similarly drawn to the protein and moisture in pet food, the Royal Entomological Society adds.

‘It’s not a sign of an unclean home; any pet bowl left out will attract them given the chance.’

Likewise, homes are also perfect breeding grounds for fruit flies.

These zooming specks lay eggs inside fruit and vegetables that then hatch into maggots, which then munch on the sludge in your drainpipes and sinks as well as, of course, your fruit bowls.

What should I do about all these flies?

It depends on who you ask.

The Royal Entomological Society recommends you put the fly swatter down as flies do more than nosedive into your face.

‘Flies turning up in our homes are doing genuinely important jobs outside. Insects shouldn’t be seen as pests by default, but as essential, undervalued parts of a healthy ecosystem,’ it says.

‘Flies are pollinators and decomposers: they break down organic waste, recycle nutrients back into the soil, and are a vital food source for birds, bats and other wildlife.’

This is why the society recommends deterring, rather than killing:

• Citrus peels: These contain the compound d-limonene, which emits a scent that scrambles the sensory receptors insects use to get around. So place a peel by the windowsill or door.
• Peppermint oil: While refreshing to us, this menthol-rich liquid is unbearable to insects. Mix it with water in a spray and spritz your doorframe and windowsills every few days.
• Keep on top of your bins: if they start to smell, put them in the shade or pour baking soda on them.
• Seal gaps in windows: This gives these speedy insects fewer ways to invade your home, experts previously told Metro.

Whittington, though, has a slightly different attitude.

‘It helps nobody to downplay the problem by claiming that flies are like bees (good pollinators) or that killing them “inhumanely” with fly traps should be replaced with buckets of water that would attract fly predators,’ he says.

‘Such comments only trivialise the problem that people experience and provide little pragmatic help.’

Instead, Whittington stresses that flies can be considered a public health risk, so it’s okay to deal with them, echoing pest control experts.

‘Traps, fly-papers and screens on windows and doors are in widespread use globally and it is questionable that any are inhumane,’ he adds, ‘but they are highly effective means of diminishing the nuisance factor.’

For Whittington, though, there’s only so much people can do.

‘Improvements of waste disposal at the community and the commercial levels are the most important way to resolve this national issue,’ he says.

Get in touch with our news team by emailing us at webnews@metro.co.uk.

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