I have often mentioned to my kids that when we were young flies were a real problem at times. Mostly because the house was kept open all summer long.
I also told them about the amazing fly spray that actually worked (unlike the ones we use now)
Yesterday I recalled two of the fly control products mum used. Trimort and Aero-Blast.
The main active ingredient was the wonder (at the time) chemical DDT.
How times changed over the coming years.
DDT was used widely on crops, swamps, houses, humans and during the war for insect control.
I found these pictures and I also added a link to a small story about DDT.
There is a vast amount of info on the web.