We live in Northern Idaho and here on ranch we have thousands and thousands of them, they are everywhere. My kids bring in ten or twenty day throughout much of the summer and let them loose in the house. Most of them go back out the windows but a lot of them just stay in the house and hunt flies and lay their eggs attached to the walls next to the planter boxes in the house.
I still can't figure out for sure what type we have though, I have been looking all morning but have been unable to find any usefull information at all.
After seeing the praying mantises in this article I think it likely ours are European, but I really don't know. I wanted to find out how long they are in the egg sacks before they hatch and at what temp they need to be to stimulate hatching, I thought it would be cool to have a bunch of them in the house through the winter.