I have magical insect repellent that prevents nuisance1,2 insects from landing on me, biting/stinging me, or congregating within, say, 1m of my face.

Would I still want to employ insect screening on areas that are always air-open to the outside? If so, why? For example, why would I want to screen in a porch, deck or swimming pool? (Screens between indoor and outdoor spaces still have the obvious use of reducing ingress into my living area, so I'm not asking about those. If it makes a difference, assume my insects are similar to those in the mountains of California.)

Let's assume I am not also trying to keep certain insects in. (That is, I am not, for example, building an open-air butterfly conservatory.)

(1 Particularly flies, mosquitos, gnats, ticks, etc.)

(2 "Non-nuisance" insects are unaffected. Butterflies, certainly, probably dragonflies, possibly moths and/or tarantulas, maybe others. It's magic, so it might even be able to change behavior based on the individual or even their mood.)

Edit 1: The intent was not to get too hung up on how the magic works, just to assume that it does, but since some folks are answering based on assumptions as to how it works, perhaps I should clarify... The magic is wearable (i.e. affects a person/animal, not an area), extremely persistent (lasts for years), it's inexpensive enough that most middle-class people wouldn't think twice about using it on pets, and one can assume that guests will "bring their own". For most purposes, and particularly from a practicality standpoint, you could substitute a really effective, inexpensive science-based rub-on/spray-on repellent.

Edit 2: I intentionally left out details in the original question, because I like seeing generally applicable answers (that's the purpose of this site, after all!). So, please don't take this as invalidating any existing answers; after all, my specific answer might be "because screening in porches is just what people do".

That said... this specific porch is a small part of a much larger deck; far too large to screen in the whole thing (most of which is anyway open to the sky). The main eating areas are in the open-to-sky areas; eating in the screened-in part would be intimate and inconvenient (it's on the opposite side of the house from the kitchen). The screened section is the only part with a normal-height roof, and is also facing a mountain slope at fairly short distance, so "shade" isn't an issue.

Any answers that address this specific situation would be awesome, however, looking at it more closely, I realize there are a number of aspects of this porch that aren't exactly practical, so for my specific case I'm leaning rather heavily toward "because it's expected" as the reason. Thus, unless I happen to get a particularly brilliant answer for my specific case, I will accept one for why this world would generally bother to screen things, so keep those coming also!


Lots of good answers, often with recurring themes; thanks! In the end I awarded Ash (largely for having the longest list of reasons), although Mike Serfas definitely gets an honorable mention, and I want to give a shout-out to Radovan Garabík for the mention of keeping bugs (and birds, squirrels, etc.) out of your swimming pool.

Ultimately, for my specific instance, I'm going with a combination of "tradition" and keeping crud out. There's a huge area of deck, but more than half is open to the sky and can take advantage of rain to do some "natural washing". The part that's screened is fairly enclosed even without screening, and is much more "intimate" than the other areas; keeping insects entirely out because someone might want to take a nap there is plausible, though perhaps an accidental benefit.

I got myself into this mess, after all, by giving my setting a screened-in porch without stopping to ask why I was screening in that, and only that, specific area. Given plenty of reason why my story-world would in general still screen in outdoor areas, I see no problem making that the in-universe explanation as well 😄.

  • $\begingroup$ I intentionally left out details in the original question, because I like seeing generally applicable answers (that's the purpose of this site, after all!). SE's purpose is to be specifically useful to multiple people. Intentionally leaving out details is justification to close a question. From the help center, questions must be specific, answerable, include context, and include restrictions/requirements. It's a temptation to use the site to overcome writer's block or fish for ideas - but both are off-topic. Thank you for including the details. $\endgroup$
    – JBH
    Commented May 2, 2021 at 21:33
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    $\begingroup$ @JBH, do you realize those statements are contradictory? The details I left out were those that made this difference between "why would this society..." and "why would this specific house...". The latter, at least to me, seems dangerously in story-based territory, and I'm strongly thinking my answer to the latter is going to be "tradition", which means the answers to the more general form are actually going to be the ones that end up being useful. (OTOH, if you're thinking about magic-related details, I'll grant you that one.) $\endgroup$
    – Matthew
    Commented May 3, 2021 at 1:42
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    $\begingroup$ So disappointed! I landed on this question from the HNQ list thinking it was the outdoors site, not world building. I really wanted to know your source for such effective bug repellant that obsoleted the need for screens. $\endgroup$
    – Caleb
    Commented May 3, 2021 at 7:15
  • $\begingroup$ "I have magical insect repellent that prevents nuisance1,2 insects from landing on me, biting/stinging me, or congregating within, say, 1m of my face." Sooo... that covers about half my body. $\endgroup$
    – NPSF3000
    Commented May 4, 2021 at 20:34

10 Answers 10


Protect against Ember Attack

This is the number one cause of house loss in Australian Bushfires - tiny smouldering bits of vegetation riding on the wind advancing up to 15km in front of a bushfire. Even city / suburban homes 10km+ from the bush are at risk.

I suspect the insect screens available in Australian hardware stores are different from other parts of the world because of this - they're categorised based on fire protection first, dimensions second, and the top end ones are made from aluminium. But "To stop my house burning down" is fairly high on the list.

Minimises cleaning:

So I like a little bit of fresh air but not full outdoors, insect screens also filter a bit of the dust. They get very dirty from dust (and real estate agents conducting inspections love telling you off for not cleaning them). The dust they catch is dust that doesn't blow into your outdoor area (and thus also house) and settle in hard to clean places.

Minor pollen filter:

They don't filter all pollen, pollen is tiny, but screens do catch some. I have pretty bad year round hayfever and the difference between a full open door and open-glass-but-screen-still-shut is notable. "Must take anti-histimine in minutes or nose will run" vs "Must take in next few hours".

Surrounding my outdoor entertaining area with these screens will reduce my dependence on anti-histamines, as less pollen gets up my nose.

Flies are filthy.

You don't want flies in your food prep area - if they've recently touched poo, you don't want them walking over your clean dishes or fruit bowl.

(Yes, outdoor kitchens are a thing.) This is also true of BBQ and outdoor grills.

Vet bills are expensive.

The insects are avoiding you - but are they avoiding your furry friends? A mosquito bite, ticks, fleas, etc can harm you pet, and thus your wallet.

An infestation that stays 1m from your face is still a problem.

A wasps nest in your walls is going to cause a problem even if they don't approach you. If for no other reason that it freaks out guests and you're sick of picking up dead wasps.

Stops birds nesting in the rafters

Birds like to nest on the rafters under verandas in outdoor areas. This results in things falling that you don't want to step in - from bird poo to shattered eggs to nest bits.

Don't share your food with birds / bugs

Outdoor dining is a thing. So is getting distracted from your dinner. When that happens, bugs and birds can take a swoop at your food.

Must be there by by-law / tenancy code.

Your guy with the magic spell doesn't care about them, but his landlord sure does. Other people have lived in the house before him, and will live in it since, and they need protection.

There can be zoning laws requiring these. I know a building I once owned a tiny apartment in there was a requirement for the screen panels to not be taken out of the balcony window except for brief cleaning. If you looked at the high rise from the ground and a few panels were missing it looked ugly.

There can also be safety laws requiring these. Australian Bushfire example again - in the high fire danger properties (basically all that aren't farms or suburbs really), you need screens in dozens of places, that auto-shut (can't be left open), and must be made of aluminium or fibreglass. It's to stop the ember attack threat.

Decent quality ones can act as a privacy screen

Insect screens also block a decent chunk of light. We have dog-proof ones and live in a medium bushfire risk suburb and they block about 50% of the light - with the lights off on one side, you can't see through them.

While skinny-dips in the pool are rare, keeping the insect screens up certainly makes it difficult for the creepy neighbour with a telescope on his roof to spy on you.

They're also a bit of shade

Every bit of sunlight you block can keep your entertaining area a bit cooler.

Insect screens do vary in shade capability but they're better than nothing.


A mozzie is very loud, even at 1m away. They will probably spend the night doing laps of you, and it will sound like trying to sleep through sirens.

Your magic spell wouldn't have stopped any of my bee stings

I've been stung twice by a bee in my life. Once on my bare foot after stepping on one accidentally, and once on my leg after resting on grass which included a dead bee, stinger pointing up.

A magic field wouldn't of protected me from either. An insect screen would have.

  • $\begingroup$ "are they avoiding your furry friends?" — well, yes, pets would have the same magic... at least, they'd be as likely to have it as pets IRL are likely to have flea collars or be given anti-insect medicine. Still, point taken. Also, though I sort-of excluded keeping things in, cat containment could be another reason. $\endgroup$
    – Matthew
    Commented May 2, 2021 at 14:36
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    $\begingroup$ what if the bees shoot out sideways at high velocity when your foot goes down? $\endgroup$ Commented May 3, 2021 at 17:31
  • $\begingroup$ Aside - I swear I'd once rear-ended the backside of a bee while cycling. Got stinger through my glove and into the knuckle. Sorry fuzzy dude. $\endgroup$
    – Criggie
    Commented May 4, 2021 at 4:20
  • $\begingroup$ @user253751, actually, I believe I have a spell that prevents or at least minimizes small cuts and punctures that would probably have prevented those stings. Totally different spell, though (also good for thorns, nails, Lego™ bricks, ...), and probably works by redistributing forces so there isn't enough localized pressure to penetrate the skin (like how you can easily lie on a bed of 10k nails, but lying on a bed of 10 is a Bad Idea). $\endgroup$
    – Matthew
    Commented May 4, 2021 at 20:31


I'm going to assume that this magic repellent can be sprayed all around the house so noise, dead insects etc. are not a problem. It genuinely keeps insects out. However...

Birds. Birds are cute, friendly visitors. People like them. They dote over them when they make it into a big box store and shop beside you. But birds do have a way of reminding you of their presence after they have gone! There's statuary in that enclosed space of yours, and the magic cleaning robot has been banned from working on it ever since the unfortunate patina incident. (But that statue was dirty, it still protests...)

Bats. Mostly the same reason, with a double helping of viral paranoia.

Spy drones. Futuristic magic technology (no wait, present technology) meets the same puerile reasons for spying as always, and occasionally, something far more sinister.

Leaves. If you invent yourself a leaf repellent, you'll have a winner in the marketplace. A repellent for neighbors with blowing machines that make 10,000 times the noise that would be inherent from a simple jet of air would be even more highly prized. (You can make it a pesticide instead if you want) For now, however, fly screens at least keep leaves out of indoor outdoor spaces.

  • $\begingroup$ Related aside: you mow your lawn by dragging a horizontal sharp(ish) stick through the grass that magically cuts the grass where it touches the stick. You could, similarly, make a magic leaf repellent, but the magic tires you out much as if you'd pushed the leaves yourself, so I'm not sure that will win over a gas or electric blower. But you've got a point about keeping leaves/twigs/etc. out when no one is around. $\endgroup$
    – Matthew
    Commented May 4, 2021 at 20:25

Screens discourage witches.

Etruscan Roman Remains in Popular Tradition

When a man is visited in sleep by witches who ride or torment him, you should fasten in the chimney a coarse linen cloth or a sieve; tie at the head of the bed a pair of woold cords or a branch of fern leaves, in which the seeds are almost ripe; sprinkle a cup of mustard seed on the door-sill. The witch must count the intersitces of the cloth or sieve, the seeds of the fern or the teeth of the cords, and must pick up every mustard seed, counting as she does so, ere she is free to torment the sleepers by knotting their feathers, riding on their breasts, or whispering to them awful dreams.

When a witch encounters a collection of small things, she is compelled to count them. It seems like this is not random natural small things but small things placed through human agency. Although this source title mentions the Etruscans this is probably witchcraft lore originating in Africa and so prevalent in the American South.

Window screens are pretty much insurmountable to compulsively counting witches and might account for why there is a lot less witch trouble in the US since the early 20th century.


For the sake of the insects

Suppose you are allergic to bees, and don't want to be stung by one. You might cast the spell to protect yourself.

But that doesn't make you anti-bee. Bees pollinate flowers. Bees feed birds. You want bees to thrive, just not near you.

Any queen bee that makes a hive near your bedroom while you are at work is going to be inconvenienced or killed when you come home, and the hive is demolished by the spell.

Better to put up screens to avoid the queen bee coming too close in the first place.


Sound. A fly bashing against a window is distracting. Mosquito buzzing can keep me awake from the other end of the room without ever stinging me. It's for peace of mind.

Cleaning. Having to clean up dead flies and other insects from your window area's is also an annoying business.

Hygiene. You won't be close to your food all the time. Worst I've found was a wasp that got into my food as I was cooking, cooked partially chopped up wasp is unpleasant to discover, and many insects you won't even notice their presence in your food until you bite down (if your food tastes funny for one or two bites you probably ate one). Also having insects relieve themselves on your food or leave pieces of their previous food on yours isn't a pleasant idea.

  • $\begingroup$ Hehe, you're making me question every unscreened picnic shelter I've ever used 😅. Alas, in my specific setting, the area I was thinking to have screened is not the eating area, and the eating areas are much too big to be screened. I'm liking the cleanliness angle, though, since the area in question is basically a walled room and thus can't take advantage of rain for natural cleaning. $\endgroup$
    – Matthew
    Commented May 2, 2021 at 14:22
  • $\begingroup$ I completely agree with you. Although, historically insects and other small critters present in food were an important source of supplemental proteins. Food-related sensitivities are a very modern thing. $\endgroup$
    – Otkin
    Commented May 2, 2021 at 19:15

Swimming pool - you do not want dead ex-insect bodies in your face when doing your daily relaxing swim, I guess...

And a mosquito buzz alone can wake you from further than 1 meter distance (source: personal experience), so you prefer to keep the screen on your windows...

  • $\begingroup$ The swimming pool in my case is actually indoors, but this is a good general answer; +1. (BTW, I did say in the question the windows separating "indoors" and "outdoors" definitely have screens, so "keep them further away" only applies if trying to sleep "outside". Then again, the non-screened parts of my deck are such that you probably wouldn't want to sleep there, while the screened area you might...) $\endgroup$
    – Matthew
    Commented May 2, 2021 at 14:43

A magical spell is active: it requires energy, or attention, or concentration, or some such.

Screens are passive: they work by making it too difficult for insects to get through (i.e., the insects would have to expend energy breaking past).

Think of it the same way you would if someone invented some electronic device that (somehow) repelled insects using (say) magnetic fields. All's well and good until the power bill comes or the dog pulls the plug out of the socket. Then you'd be wishing you'd just put up a screen...



You don't want to cast it for everyone who walks in, or else they would object to having you cast it. For whatever reason. Time would probably be the simplest. Or it just is considered polite to not show off your magic.


You have to keep on casting the spell. Screens, it's one and done.

Other harm

Screens keep flies away from the food even when you aren't there. And so on.


Screens are a backup.

Spells may fail. They may consume resources you can run out off. They may need regular recasting, but you absolutely need 8 hours of beauty sleep. Or they need regular recasting, but just like your daily pills, you often forget to recast them. They may not work well on toddlers and babies. They fail to be effective when you use the microwave. And your WiFi works a lot better when you drop the spell.

Secrecy and/or vanity.

You don't want your neighbours to know you're casting that spell. Or the IRS. Perhaps there's a tax to be paid on each spell cast, and you really hate to part with you hard earned doubloons. You want to give the impression to don't need this spell. It's only plebs who use this spell, and you'd never admit you use it. You still use it, but the screens give you deniability towards the neighbourhood and the taxman.


You bought the house with the screens. Why bother removing them? And besides, during the holiday season, you can hang decorations from them.

  • $\begingroup$ "Perhaps there's a tax to be paid on each spell cast" — nope, no tax on using magic. OTOH, most people can't, and have to buy spells, which I expect are subject to at least sales tax like anything else 😁. (Although, I actually haven't thought about whether or not there is sales tax in my world; it hasn't been, and isn't likely to be, relevant.) Some interesting ideas, though! $\endgroup$
    – Matthew
    Commented May 3, 2021 at 1:45

A cyberwizard approach: a screen would prevent attack from tiny things that aren't bugs. Example: tiny machines escape the magical barrier, because the spell only pushes away living creatures. Another poster mentioned fire embers carried on the wind.

Also, you might be able to prevent bugs from annoying you, but what about bird poop? No, seriously-- I've stood under one of the most massive flight of bats in the USA leaving their cave. The bats happily ate all the bugs in the area. However, the bats above me managed to poop on my head. I'm not kidding. The shame!

  • 1
    $\begingroup$ Non-living "insects" aren't a concern, but if they were, the spell would get adjusted accordingly. Keeping things out when there aren't people around seems to be the main motive. (Hmm, you could have a spell to prevent you being pooped on; I don't think most people would bother, however.) $\endgroup$
    – Matthew
    Commented May 4, 2021 at 20:15

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