Praying mantises are generalist predators that eat a wide range of insects, which makes them fascinating garden residents but surprisingly limited as targeted pest control. Their real value spans broader territory: they play a role in local food webs, they’ve inspired robotics research, and they’ve been used in traditional medicine for nearly 2,000 years.
Pest Control: Helpful but Overrated
Garden supply stores and online retailers commonly sell mantis egg cases as natural pest control agents. The idea is appealing: release mantises into your garden and let them eat the bugs destroying your plants. Young mantises do eat tiny pests like aphids and whiteflies aggressively. But as they grow larger, they stop bothering with small insects and shift to bigger prey.
The core problem is that mantises are completely indiscriminate hunters. They don’t distinguish between pests and beneficial insects. A mantis will just as happily eat a bee pollinating your tomatoes as a caterpillar chewing your leaves. NC State Extension states plainly that mantises “are not useful for pest management” because of this indiscriminate feeding. If you’re looking for targeted biological pest control, ladybugs (for aphids) or parasitic wasps (for caterpillars) are far more effective choices.
That said, mantises aren’t worthless in a garden. They do reduce the overall insect population in a small area, and watching them hunt is genuinely entertaining. Just don’t expect them to solve a specific pest problem.
Their Role in the Food Web
Mantises sit in the middle of local ecosystems, functioning as both predator and prey. They consume insects, spiders, and in the case of larger species, surprisingly big animals. Chinese mantises, which can reach 5 inches long, have been documented feeding on over 20 species of small birds, including hummingbirds. They also eat mice, small reptiles, and amphibians.
Mantises themselves are food for birds, bats, lizards, frogs, and spiders. This makes them an energy bridge in the food chain, converting smaller prey into meals for larger animals. In a healthy ecosystem, mantises contribute to the balance of insect populations even if they aren’t selective about which insects they take.
Native vs. Invasive Species Matter
Not all mantises play the same ecological role, and this distinction matters if you’re thinking about releasing them. The Carolina mantis is the only species native to the eastern United States. It’s relatively small, about 2 to 3 inches long, with wings that reach only two-thirds of its body length. The Chinese mantis, introduced from Asia, grows to 5 inches and has become so numerous in many areas that it preys on and outcompetes native Carolina mantises.
Because Chinese mantises are so large, their predation on bees, butterflies, hummingbirds, and other wildlife causes real ecological harm. The Carolina mantis, being much smaller, has far less impact on these animals. When garden stores sell mantis egg cases, they’re often selling Chinese or European mantis species, which means buying and releasing them can actively harm your local ecosystem. If you already have native mantises in your yard, introducing larger invasive species puts those natives at risk.
Inspiring Robotics and 3D Vision
Praying mantises are one of the only insects known to see in three dimensions, and the way they do it turns out to be entirely different from how human 3D vision works. Researchers at Newcastle University fitted mantises with tiny 3D glasses (yes, really) and discovered that mantis stereo vision is based on detecting changes over time rather than comparing static images from two eyes. This was a completely new form of 3D vision previously unknown to science.
This discovery has practical implications for robotics. Many robots use stereo vision to navigate, but the systems are typically modeled on human vision, which requires significant computing power. Because mantis brains are tiny, their version of stereo vision needs very little processing. Engineers are exploring how to apply this approach to low-power autonomous robots that need to navigate without heavy onboard computers. The same research team also built an electronic mantis arm that mimics the insect’s striking motion, which completes in as little as 60 milliseconds and involves a four-phase sequence of approach, thrust, capture, and retraction.
Traditional Chinese Medicine
Mantis egg cases, called “sang piao xiao,” have been used in traditional Chinese medicine since at least 100 AD, when they were described in the Shennong Bencao Jing, one of the oldest Chinese pharmacological texts. The egg cases are used in formulas sold as both powders and pills. Their medicinal use may have originated from their occasional appearance on mulberry plants, which were already valued in Chinese herbology. While this represents a long cultural tradition, these uses haven’t been validated through modern clinical research.
What Mantises Are Actually Best For
If you strip away the marketing around pest control, mantises are most valuable as a general part of a healthy garden ecosystem, not as a targeted solution to any particular problem. Their greatest contributions are indirect: supporting food webs, keeping overall insect numbers in check across many species, and providing a window into remarkable biology. A mantis can adjust its strike mid-attack based on prey movement, halt a mistimed strike before it completes, and process 3D visual information with a brain smaller than a pinhead.
If you find mantises in your garden naturally, they’re a sign of a functioning ecosystem. If you’re tempted to buy egg cases online, consider that you may be introducing invasive species that harm native mantises and kill pollinators your garden depends on. The best approach is to encourage the mantises already living in your area by reducing pesticide use and maintaining diverse plantings that support a range of insects.