‘Gross’: Why do flies land on our back in summer?

Summer is almost here, so you might be finding yourself doing more swatting. But why do they like our backs so much?

While the weather might still seem confused, summer is less than one month away and we’re starting to notice everything it brings with it.

Sunny skies (usually), longer days, warmer weather, and flies.

So many flies.

If you’ve been finding yourself swatting the air more often, or battling your way inside while a swarm of the small, incessant creatures crowd around your doorway, it’s a sure sign that the heat and humidity are back.

But why do flies love us so much?

They seem to congregate on our backs, around our eyes, on the rims of our coffee mugs, and anywhere else they can manage before we start swatting.

Brace yourself for the answer – it’s pretty gross.

Flies like to suck up secretions on our skin.

A fly has a very soft, fleshy mouth, which is less suited to biting and instead sucks up sweat and dead skin cells that might contain proteins, carbohydrates, salts and sugars for them.

This proclivity for sweat and salt means the more someone sweats, the more likely flies are to land on them.

They also like to land on your back because it’s a larger surface area that’s relatively still, giving them time to seek out the oils or cells they’re seeking.

Flies like our backs because they’re relatively still. Picture: Reddit/iStock.

Certain types of flies also get nutrients from sitting around the eyes of livestock, which will make sense if you’ve ever seen a horse or a cow up close in the summer.

However, given how hairy these animals are, they can’t really feed on anything else.

They like human skin because it’s less hairy, and therefore easier to use for sustenance.

What happens when flies land on food?

The process is a bit different when flies land on food.

They taste using their feet, so if they want to consume something, they’ll land on it to try it out.

Fruit flies attack a banana. Picture: iStock.

From there, they can’t chew it, so they vomit on it to liquefy the solid food and then chow it down.

This is why you shouldn’t eat food if you’ve had flies touching it.

That, and the fact that they’ll regularly sit on things like animal faeces or rotting rubbish – the transfer of those germs is definitely not worth it.

How can we best keep fly-free?

There’s a few answers to this question, beginning with behaviours that’ll keep flies disinterested in your home.

Keep your home, particularly your kitchen, clean to avoid masses of flies.

If you have a pet, you need to keep on top of its mess to keep flies from lingering.

Also, make sure you dispose of food that’s been kept out, keep your kitchen surfaces and sink nice and clean, and regularly empty out your rubbish bins to keep flies away.

Beyond these preventive measures, keep your doors and windows closed, and keep an eye on your fly screens for any holes.

If you’re still having trouble with flies, you can buy “zappers” that’ll kill them for you, or use things like citronella candles to limit the intensity of the fly population around you.

Originally published as ‘Gross’: Why do flies land on our back in summer?