Most Mantis?
NO.
Some smaller species, sure.
How tall is the tank? If you have all 3 dimensions, then you can calulate the volume, which is the real first step.
LxWxH, divided by 231 in gallons.
That being said, I had a 2" (if even that) N. Wenn in a 1.5 gallon hex for a few months, he was fine. I moved him into a bigger tank a few weeks back, and he seems very happy with the expanded digs.
Dr. Caldwel keeps them in small containers for reasearch, with frequent water changes, but if you want an animal that will 'show off' for you, a bigger area in in order.
-Ronl