praying mantises are awesome insect hunters. problem is they're not picky with what they wanna eat. they'll eat anything that looks like food. which is any insect whether pest or beneficial.
I bought a praying mantis egg case last winter. They hatched out in the greenhouse and as the weather warmed up I moved some out into the garden. They grew to be several inches long and laid many egg cases on my pepper plants. I saved several and some have already hatched in the greenhouse. Have a few more stored in the fridge to let hatch later this Spring.
Beneficial and really cool bugs to watch. Also have ladybugs and haven't seen any conflict between the two.