# Strange Housefly Behaviour **URL:** \ **Category:** Factual Questions\ **Created:** [May 22, 2007, 8:55pm UTC](https://boards.straightdope.com/t/strange-housefly-behaviour/405135 "2007-05-22T20:55:49Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![Chez\_Guevara](https://avatars.discourse-cdn.com/v4/letter/c/aeb1de/32.png) [@Chez\_Guevara](https://boards.straightdope.com/u/Chez_Guevara)\ **Post date:** [May 22, 2007, 8:55pm UTC](https://boards.straightdope.com/t/strange-housefly-behaviour/405135/1 "2007-05-22T20:55:49Z")
This happens every year between April and September. On coming downstairs in the morning no flies are visible in the open plan living area. I open a window, or the external door, and within 15 minutes about two dozen flies can be observed flying around erratically close to the ceiling. They occupy a small area at the centre of the living space, say 4’ by 4’. The rest of the room is unaffected, as are all the other rooms in the house. There is nothing notable about the territory colonised by these flies. The room is beamed at the ceiling and there is no light fitting installed there. My standards of household hygiene are, of course, impeccable. I’m not so much requesting hints on controlling these flies as I am curious to know why they behave in this way. If anyone has a clue then please advise accordingly. Many thanks. ---
**Author:** ![ZipperJJ](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/zipperjj/32/211_2.png) [@ZipperJJ](https://boards.straightdope.com/u/ZipperJJ)\ **Post date:** [May 22, 2007, 8:59pm UTC](https://boards.straightdope.com/t/strange-housefly-behaviour/405135/2 "2007-05-22T20:59:39Z")
If you watch _CSI_, reason would tell you there is a body part in your ceiling. Just sayin’… ---
**Author:** ![Joey\_P](https://avatars.discourse-cdn.com/v4/letter/j/919ad9/32.png) [@Joey\_P](https://boards.straightdope.com/u/Joey_P)\ **Post date:** [May 22, 2007, 9:04pm UTC](https://boards.straightdope.com/t/strange-housefly-behaviour/405135/3 "2007-05-22T21:04:15Z")
[QUOTE=Chez Guevara] My standards of household hygiene are, of course, impeccable. [/QUOTE] We wouldn’t have expected less. If they do this every year, I’m guessing there’s _something_ there. Can you get up near the ceiling and smell it, touch it and check for dampness, maybe get up in the attic and check to see if there’s something going on above it. ---
**Author:** ![Squink](https://avatars.discourse-cdn.com/v4/letter/s/b5e925/32.png) [@Squink](https://boards.straightdope.com/u/Squink)\ **Post date:** [May 22, 2007, 9:38pm UTC](https://boards.straightdope.com/t/strange-housefly-behaviour/405135/4 "2007-05-22T21:38:28Z")
Your houseflies may be seeing and responding to something that you can’t: > [@](#): > > We have measured the spectral sensitivity of the housefly, Musca domestica, another > species known to be strongly phototactic to near-ultraviolet wavelengths (Cameron, > 1938) and to be attracted to light traps emitting primarily the 254 nm. mercury line > (Deay & Taylor, 1962). [PDF](http://jeb.biologists.org/cgi/reprint/49/3/669.pdf) ---
**Author:** ![Kneepants\_Erasmus\_the\_Humanist](https://avatars.discourse-cdn.com/v4/letter/k/54ee81/32.png) [@Kneepants\_Erasmus\_the\_Humanist](https://boards.straightdope.com/u/Kneepants_Erasmus_the_Humanist)\ **Post date:** [May 22, 2007, 11:11pm UTC](https://boards.straightdope.com/t/strange-housefly-behaviour/405135/5 "2007-05-22T23:11:59Z")
EEEP! I think I would be very afraid to check the attic. Surely you would smell a dead rat/other animal. Surely you wouldn’t have a freshly dead rat/other animal in the same spot of your attic every year from April to September… I got nothing. ---
**Author:** ![RedSwinglineOne](https://avatars.discourse-cdn.com/v4/letter/r/a9adbd/32.png) [@RedSwinglineOne](https://boards.straightdope.com/u/RedSwinglineOne)\ **Post date:** [May 22, 2007, 11:26pm UTC](https://boards.straightdope.com/t/strange-housefly-behaviour/405135/6 "2007-05-22T23:26:10Z")
From [build a better flytrap](http://findarticles.com/p/articles/mi_qa3666/is_200003/ai_n8880664) > [@](#): > > the air seems to attract flies more than a scent. … In windy areas, all flies will travel outside their territory to seek a calmer atmosphere. I have noticed flies will often fly into my garage if I leave the door open when it is windy and (the flies) just fly in circles… ---
**Author:** ![Chez\_Guevara](https://avatars.discourse-cdn.com/v4/letter/c/aeb1de/32.png) [@Chez\_Guevara](https://boards.straightdope.com/u/Chez_Guevara)\ **Post date:** [May 23, 2007, 5:19pm UTC](https://boards.straightdope.com/t/strange-housefly-behaviour/405135/7 "2007-05-23T17:19:29Z")
I forgot to mention that the flies only congregate in sunny weather. On dull, overcast days with the door and windows open they are _in absentia_. Furthermore the windy conditions as described by **RedSwinglineOne** do not apply in this case as today is calm and the flies are in attendance as per usual. There is no attic in the house as such but this may be irrelevant since the Fly Zone described in the OP is beneath the (upstairs) master bedroom. Now, there are items under my bed which I do not wish to discuss on a public message board, but I’m reasonably sure that an animal is not among them, especially a dead one. In the absence of a more persuasive reason for the presence of these flies, and I’m still trying to digest the link of **Squink** , I believe it’s possible that the cause can be put down to religious fervour. This area of the living room is probably a shrine of some kind which the flies come to worship. The fact that they only come when the weather is fine is clearly an example of insects imitating human behaviour. As an interim solution I decided to hang an effigy of a spider in the affected area in order to test the flies’ faith. Regrettably I don’t have such an effigy handy right now so I’ve nailed a toy frog to the beam instead. The frog moves its limbs and opens its mouth when you pull a cord at the bottom. We’ll see if this works. ---
**Author:** ![Squink](https://avatars.discourse-cdn.com/v4/letter/s/b5e925/32.png) [@Squink](https://boards.straightdope.com/u/Squink)\ **Post date:** [May 23, 2007, 5:26pm UTC](https://boards.straightdope.com/t/strange-housefly-behaviour/405135/8 "2007-05-23T17:26:30Z")
[QUOTE=Chez Guevara] I’m still trying to digest the link of **Squink** [/QUOTE] Someone in the past may have sprayed something that fluoresces in the UV, an air freshener or touch up paint, on that part of the ceiling. That’d make that bit of ceiling appear brighter than the rest, on sunny days.