Most species of praying mantises are not big enough to kill a hummingbird. There is one exception that I know of where the female is large enough, and has been photographed in the act, but seldom does so since there is so much other prey available.
There is an invasive Chinese mantis species established in the US and if memory serves, that is the one that is large enough to capture a hummingbird.
See my post #30.