I introduced mantis eggs onto our 5 acres here in northern Illinois about 10 years ago and they have been with us ever since, surviving the sometimes brutal (-30F) winters. They don't consume a large number of insects like bats or ladybugs, but are welcome. They seem to like the mix of young evergreen and native hardwoods, where I see the most egg sacks in the fall & winter.
I was very glad to read this very interesting article on this insect. As a student, we had learnt of the very savage be-heading act of the females after mating, but I had never seen one (Ontario, Canada) until about two weeks ago. I "happened" upon it as I was pruning, on a peony bush. Unfortunately, I did not have my camera with me and of course, when I returned with my camera it was gone. It is good to know they survive in these climates - I will be on the lookout for them in future.