Why Do Flies Fly Toward and Land on People?

Q: So here’s something that I’ve always wondered and I know I’m not alone in this: Given that I don’t look or smell like a pile of dog poop and that my home isn’t subject to demonic possession, why do houseflies insist on flying toward and landing on me? This has always baffled me since they, or at least most flies that I encounter, don’t bite a la mosquitoes or horseflies and don’t seem to really “want” anything other than to drive me nuts. Is their something that attracts them toward humans? Or do they just take great joy in being aggressively annoying? Are there any easy ways that I can make my home a “no fly” zone?

The lady of the flies,

Veronica, Windsor, Ontario

Hey Veronica,

I’ve always wondered the same thing. No matter how many times you shoo, swat and scream, “What do you want from me? Go away!” flies just never seem to get the point. They just keep on coming back for more. Given that the common housefly doesn’t have any interest in sucking blood (feeding on open wounds is a different story) you think they’d fly away from humans. After all, we’re a lot larger, more intimidating and come brandishing swatters.

The fact of the matter is that houseflies are scavengers and land on us because, well, they like us: The human body, like some of their favorite food sources -- feces, food and rotting flesh -- radiates a sense of warmth and nourishment. And while not interested in biting (they don’t have the equipment for that), the common housefly, or musca domestica, does want to suck up the salt, dead skin, oil and whatever they find edible on the exposed epidermis with their straw-like tongues.

Thanks to hearty appetites aided by an excellent sense of smell and a pair of complex eyes that cover half of their heads, houseflies also land on us and everything else in sight because they’re constantly on the hunt for a nice warm place to poop, vomit (they vomit on solid foods to liquefy it and make it edible) and lay eggs. This charming land-and-defecate-everywhere routine has made flies vectors of communicable diseases, ranging from typhoid to tuberculosis. The pathogens transmitted by houseflies, picked up after feasting on things like dung heaps and dead animals, are carried on their legs and around their mouths. Think about it: Each time a fly lands on your arm or takes a stroll around the rim of your mug of morning coffee, it could be shaking a whole lot of germs off of its hairy little legs. Houseflies aren’t just annoying, Veronica; they can be quite dangerous.

The easiest, most inexpensive way to make the area in and around your home a “no fly” zone as you put it is to take basic preventative measures. If you have a dog and aren’t quick to pick up and dispose of its poop you should start making this your number one priority. There’s a reason why the filthy, winged critters love dog poop: It serves as both an all-you-can-eat buffet and an ideal egg depository. Also, don’t leave food out for too long, maintain a clean and tidy house (pay special attention to kitchen surfaces), empty your garbage cans regularly and keep an eye out for organic rotting matter. It’s about keeping a spic-and-span, sanitary home.

If houseflies keep on inviting themselves into your home, you should obviously shut windows and doors but also check for cracks and holes (particularly around window screens) that they might be using as a secret “back door.” I’d avoid using chemical pesticides but do recommend trying out a DIY fly trap or homemade flypaper. Non-zapping traps that use ultraviolet light to attract flies are also a great option.

Hope this helps out, Veronica. For additional resources on how to deal with these disease-carrying poop-and-vomiting machines, check out howtogetridofstuff.com and the Illinois Department of Public Health’s fly prevention and control page.

Happy shooing and swatting!

— Matt