Flies in windowsill

d0nkeyk0ng

https://imgur.com/gallery/M0T1g6X

These have appeared in our bathroom window sill for her past week, maybe every two days. We thought they might be from outside but we kept the window shut before heading out and upon our arrival, they’re back. I can’t see anything in around the toilet pan and I’m not sure where they are coming from. 

Are they cluster flies? Or something else?

TELLIT01

I've had a similar problem but with small bees appearing on the landing windowsill.  No gaps for them to come through so have no idea where they are coming from.

twopenny

There are two possibilities that I know.

That they are coming in through an open door or window elsewhere ie kitchen, front, and making their way to a window to get out. This happens in my house and no idea why it's the same window they choose.

Or there were eggs laid in some crack or crevis. I had this in my bedroom in the last place. Never could see where they were coming from and there were a large bunch every morning for a couple of weeks. I made sure they all made and exit and it never happened again.

Apodemus

They could be cluster flies, but the pic is not clear enough to be sure.  Do you live in a rural location?  If they are cluster flies, then they will be coming from wherever they were hibernating over the winter.  The best thing would be simply to leave the window open - they just want out!  For next winter, it might be good to find out where they were hibernating and see if you can block up their means of entry.  Is there any means of access from your bathroom to the loft - possibly extractor vent, gap around a heating pipe or something similar?

koalakoala

Have to agree with Apodemus. I once had a rural house and one day dozens appeared out of the extractor fan ! It was disgusting. Some mesh sorted it out.

d0nkeyk0ng

Apodemus said:

They could be cluster flies, but the pic is not clear enough to be sure.  Do you live in a rural location?    Is there any means of access from your bathroom to the loft - possibly extractor vent, gap around a heating pipe or something similar?

We live in a town. Some greenery nearby but it’s all houses and shops in a one mile radius around us. I wrote bathroom but it’s a single toilet room. No sink. The bathroom is next door with pipes from the boiler, shower etc. If the flies are coming from the loft, it’ll be from the light fixture. 

d0nkeyk0ng

So to update so far:

Windows shut all day - no flies when I came home. Used the loo but kept the window shut. No flies. Two hours later - flies on window sill. Been into loft and checked under insulation - no flies. So not from outside. Probably not from loft. Either from toilet or around toilet. The only things in the room are the light fixture, switch, toilet with waste pipe and inlet feed. Bathroom next to it is completely unaffected as is the hallway.

Puzzling.

goldfinches

Have a look at the underside of the toilet cistern lid and around the top of the water, if no luck there try keeping the door of the room closed and see if that changes anything tomorrow.

d0nkeyk0ng

I took the lid off the cistern and it was all clear, as well behind the cistern. I need a decent torch to look under and around the cistern and toilet so will look tomorrow. The only other thought I had was whether they were coming through the toilet waste as I had the lid closed all day until I came home.