It's nearly impossible to kill scorpions, the only way to get rid of them is get rid of the insects they eat-they love crickets, so if you have a cricket population work on that.

Thank god our scorpions are not as bad as those in Arizona. I was SO careful when I built my house to calk ever board on the floor and every wall hole that electricians and plumbers put in. So far it is a problem that stays outside.

A long time ago I used to have tons of scorpions around my house. When I would walk outside and shine a black light on the wall I would see 5-6 in just 1 section of the wall. The only thing I've ever had work on them as a residual (meaning it kills them when they walk where you sprayed) was Demand CS. Problem with it is it's a bit pricey and doesn't have a long shelf life (even with the lid very tightly closed it dried up on me within a year or two). It was the first time I found dead scorpions on my patio that I hadn't personally killed. Nowadays the most I find when searching for them is maybe 3 a month.

If you want an insecticide that kills them as a contact spray, try permethrin. It has a very long shelf life. I mix a small amount of that into a spray bottle with water and it kills them within 45 seconds to a minute. I'm pretty sure it doesn't have a residual effect though.

I should add: if you go the residual poison route, keep the poison away from flowering plants as that's the stuff that kills whole bee colonies. It doesn't kill the bee when it lands on the flower but the bee will bring it back to the hive and later kills them off.