Has it got weaker or have flies, wasps etc developed a resistance to it ?
I had my first visitor three weeks back and I drenched him with Raid, the bugger wouldn't stop moving, he put up a hell of a fight and I had to take drastic steps in the end. He didn't move after that.
No, I'm not cruel, I'll go out of my way to ensure a Bee leaves my house safe and sound, but wasps are evil, my mate calls them Satan's Children. Sounds like a chapter of Hells Angels !