Quotes from the What's That Bug site:
"All American species belong to the family Mantidae."
"I now believe that the Norwegian name "kneeler" is from the same reason we say "praying" mantis: you kneel when you pray. At least if you accept the "praying" spelling. At least it makes sense. Why didn't I think of that before?"
Q: "Thanks a lot for your explanation. And what is the correct spelling? "Preying" or "praying?" Both of them make sense."
A: "Both spellings are correct, depending upon the author. I prefer to spotlight the hunting versus the religious connotation."
This author will call it a PRAYING Mantis. How sweet....