Recently in the month of July my Mum & her sister who lives half a mile away both had a large influx of rather docile flies. A pest control man said they were rain-flies & would be gone in a couple of ...
I'm no entomologist, but I think the pest control man was having a bit of fun with your Mum and sister. So far as I know, a rain fly is the part of a tent that goes over the tent itself to shed rain and also to help shade the interior and keep it cooler and dryer.