What are these circling bugs?

May 24, 2004 3:15 PM

When I open the doors and windows sometimes these little gnats/flies come in and proceed to fly in small circles in the center of the room. I am sure many of you are familiar with this. What are they? Why are they doing this? (more inside)

Not only are they irksome but shouldnt they be out looking for food? How does flying in a small circle help them survive in any way? Why the center of the room? Thanks.

posted by vacapinta to science & nature (13 answers total)

What's in the room, any plants? Do your neighbors have this problem too?
posted by thomcatspike at 3:23 PM on May 24, 2004

They're just another species of fly. But they're less repulsive because they're small and the details are obscured.

As for the MI:

They'll eat later. Because they're humping. They're in the center of the room because flies mate while flying in circles and a room is open enough to do this, but enclosed enough so that they can find each other.

Larger houseflies, greenheads, etc are mating when you see them flying in circles around garbage, dog poop and stinky people. The tiny flies are there, too, but you don't notice them until they're away from garbage and in a confined space.
posted by Mayor Curley at 3:29 PM on May 24, 2004

There is nothing in the center of the room. By center, I also mean midway between floor and ceiling. I have seen this in empty rooms in other houses I have lived in too and in other people's houses. They are not flies but more like gnats.

Also, they don't actually circle, per se, so much as fly straight then turn abruptly - so its more like a square or rectangle that they trace out.
posted by vacapinta at 3:30 PM on May 24, 2004

Mhhh I guess they're fruitflies ?
posted by elpapacito at 3:48 PM on May 24, 2004

Sure they are gnats, had them in California on our patio's, come out when the humidity is up.
posted by thomcatspike at 3:58 PM on May 24, 2004

Hey, does this help?

Why do clouds of gnats always hover around a fixed point in mid-air?

"Dear Cecil:

Can you explain why gnats often gather together in large groups in mid-air, hover around an imaginary fixed point? Even if you wave your hand through a group of them and confuse their sense of locus, they return to regroup around the same point. --Alan D., Chicago

Cecil replies:

As you undoubtedly know, Alan, "gnat" is an imprecise term referring to several species of small flies, most often the fruit flies of the family Trypetidae.

The swarming is part of a mating ritual common to many insect species wherein the males hover en masse and await the females.

It's believed the insects orient themselves over or near some easily recognizable topographical feature--a white object against a field of green, for example, or a tall bush--rather than some "imaginary fixed point."

Their uncanny persistence in doing so may be attributed to the fact that they have to propagate the species (and get in what giggles they can) in an extremely short time--gnats only live for a few weeks.

Keep all this in mind next time you're tempted to spoil some little fly's fun by waving your hand through his orgy. Creep.

--CECIL ADAMS"


I love the Straight Dope and have read through their archives a couple of times. (Yes, I need to get a life, I know.) Eventually I'm going to remember to get one of the books and thus get some money to the author...
posted by batgrlHG at 8:47 PM on May 24, 2004 [1 favorite]

I firmly believe fruit flies are parthenogenic. It's the only explanation for how they can appear out of nowhere within the space of an hour of bringing fruit home.

My home can go for months without any sign of fruit flies, especially in the middle of winter or when the house has hit 45C when I've been on summer vacation.

Bring a piece of fruit into the house, and whammo! there are fruit flies. They sure as hell didn't come in on the fruit, ergo they must spontaneously be called into existence via the mere presence of fruit.

Downright spooky.
posted by five fresh fish at 9:33 PM on May 24, 2004

Do I get some sort of special recognition for providing the correct answer and receiving a "Naw, that's not it"?

Thanks for vindicating me, batgrl!
posted by Mayor Curley at 10:08 PM on May 24, 2004

Thanks all, especially Mayor Curley and batgrlHG! That's the answer I was looking for.
posted by vacapinta at 10:27 PM on May 24, 2004

It was actually reading you, Mayor, that made me think "hmmm, swarm of bugs, having sex - I read that a few weeks ago, didn't I?"

If I was really with it I'd find something to quote from Dr. Tatiana's Sex Advice to All Creation which has tons of fun info on insect sex. Oh, I can't help myself - here's a bit:

"Dear Dr. Tatiana,
I'm a true armyworm moth, and I've gone deaf in one ear. I've read this is from having too much sex. Trouble is, I'm (sob) still a virgin. So what's happening to me?
[signed,] Piqued in Darwin

...Be assured, you have nothing to worry about. It's just that your inner ear is now hosting a torrid, incestuous orgy. ...What happened it that one evening when you stopped to sip nectar from a flower, a mite scrambled up your tongue as if it were a ladder. When she reached your face, she crawled through the tangle of your scales and hairs to the outer caverns of your ears; after inspecting both, she chose one and crept inside. Then she stepped up to the delicate membrane - the tympanic membrane - that screens off the inner ear from the outer ear, and she pierced it. In doing so she destroyed forever your ability to hear with that ear.

After settling in and perhaps taking a light supper of - I'm afraid - your blood, she started to lay her eggs, about eighty in all. A couple of days later, the eggs hatched, the little larval mites wriggling backward out of their eggshells. First to emerge were the males of the brood; then came all their sisters. The males grew up faster than their sisters, prepared one of the innermost galleries of your ear as a bedchamber, carried their sister-brides thence, and even helped them out of their old skins as they finished their final molts into adulthood.

...Soon after their ecstatic orgies are done, these males die, usually without having left their natal... ear. I'm afraid, dear moth, that once your tenants have disembarked onto scented blossoms to wait for the passing of a fresh host, their brothers' rotting bodies will remain, a leprous ghost colony in the inner porches of your damaged ear."


Freaky, huh? Can't find anything about family Trypetidae yet - still looking - I remember something in here somewhere...
posted by batgrlHG at 10:31 PM on May 24, 2004 [2 favorites]

I'm glad I posed this question if for no other reason than to read that! :)
posted by vacapinta at 11:25 PM on May 24, 2004

Moths have tympanic membranes? I'm doubtful. That would imply they also have inner ear bones, would it not?
posted by five fresh fish at 9:26 AM on May 25, 2004

Not to mention, how do you give a hearing test to a moth? Perhaps there's just an assumption of deafness, with all that set up in the ear and the membrane pierced? And perhaps instead of a true tympanic membrane it's the insect equivalent?

Oops sorry, this isn't really limiting my comments to the answer to the original question. I'm a bad, bad AskMe commenter and hang my head in shame for going off on random tangents.
(But the Dr. Titania book is very amusing and does contain some info on fruitflies.)
posted by batgrlHG at 9:48 AM on May 25, 2004