There are approximately 2,000 known species of praying mantis in the United States, none of which are endangered. It has never been illegal to kill a praying mantis in any US states, and there is no fine for killing the praying mantis.
The praying mantis gets its name from the way it holds their front legs in a praying position while at rest. They are often seen as beneficial insects because they eat pests that can destroy a home garden. While there are no laws that prevent people for killing them, there is no reason to kill these beneficial insects. Two states in the US have a praying mantis as their state insects: Connecticut and South Carolina.