The only one I saw on the ground this year, I hit with the lawnmower. My first thought as I came up on it with the mower was "grasshopper" ! A split second later and the mower was over the top of it . . :/
It is probably easier to spot them flying. Once they have settled, a mantis moves so slowly and blends in so well that they are hard to see. But, you have to think twice about what you are seeing when they are on the wing!
If you find yourself thinking, "What the heck is that?! Sure is a Big Bug!" You may have just seen a mantis . . . and might enjoy tracking it down.
I used to work right in the downtown of a medium sized city. I was constantly seeing hawks. They were Sharp-shinned hawks, for the most part. Whenever I'd mention them to anyone, I'd just get a "never seen 'em." No, no! Look! Yes, they almost look like pigeons but look again!
Steve