Praying mantises eat insects. They are so good at it they are often released by farmers and gardeners as a form of organic pest control.
The body of a praying mantis is shaped by its specialized role as a predator insect. The praying posture that the mantises are named for allows them to quickly snatch prey insects with their outstretched arms at lightning speed. Their green exoskeletons may seem outlandishly bright, but in their favored stalking grounds, they blend right in with the leaves and other plant matter.
Common mantis prey include mites and aphids, grasshoppers and leafhoppers, caterpillars, moths, butterflies and crickets. All these are pest insects that feed upon vegetables and destroy crops. The voracious appetite of a praying mantis keeps these pest populations under control. However, praying mantises are indiscriminate in their appetites and may also eat insects considered beneficial to humans, such as ladybugs.
Of course, the most infamous example of praying mantises eating other insects is cannibalism: after mating, the female mantis will turn around and consume the male mantis, starting with the head. This seems like a very counterproductive mating strategy for the male, but his body contains nutrients that increase the likelihood that his offspring will live to reproduce themselves.