Mantids are top predators in a food chain of other insects and even vertebrates such as small mammals, birds, or reptiles. Using large, compound eyes that are widely spaced for binocular vision, they swivel their heads as far as 180 degrees to spot prey. Most mantids are ambush predators, sitting still and waiting for prey to come close. Their long front legs are armed with rows of sharp spines that they use to grab and impale the prey. A few mantids actively chase prey, running after them on long legs. Once captured, prey are eaten alive, sliced and chewed up piece by piece. Wiggling prey may be eaten head-first . When at rest, mantids fold their long legs beneath them in a prayer-like position, or sit cleaning their legs with their mouths. Sometimes mantids eat each other (cannibalism), such as females that occasionally devour males during mating or hatchlings that cannibalize each other.

Insects are by far the most diverse and abundant group of organisms on Earth. More than one million insect species have been identified, and estimates of how many species exist range into the tens of millions. Insects got their start way back, in the Paleozoic (about 500 million years ago) and have evolved in tandem with flowers (coevolution). Insects have become specialized on particular flowers, leading to complex sets of adaptations that couple them in a feeding and pollination relationship (a mutualism). Specialization allows for many types of insects to live in the same habitat, accommodating their exceptional biodiversity. In a backyard in the temperate zone, one might find several thousand species of insects. Specialization can occur within one plant species as well, with different insects using different parts of the plant. In just one species of tropical tree, Dr. Terry Erwin of Smithsonian's National Museum of Natural History found about a thousand species of beetles.