Praying Mantises – Friend or Foe?

Photo by William Warby on Unsplash

I’ve been thinking a lot about praying mantises. Yes, it’s true! Somewhat odd, I guess, rather unexpected, but true. I’m decidedly in awe of their hunting abilities and strangely adorable faces. But that’s not why I’ve been thinking about them lately. It’s all my son’s fault.

The Fascinating World of Ants… to a 9 year old

Somehow, my 9 year old son has become enamored with ants. I’m not sure how it happened. There was mention of a few ant facts; the discovery of an ant game on the iPad; interest in some ant hills near the house. And then, all of a sudden, there were videos on YouTube about ant colonies, ant books from the library, more iPad games with ants, intense study and wonder at the ant colonies outside our house, crackers hand-delivered to their metaphorical doorsteps – and absolute horror at the thought of anyone in the family killing ants, even those found inside the house. Which I have always maintained are fair game for dispatching. Now I was crouched on the floor with a piece of paper and a glass cup trying to scoop up tiny sugar ants to bring them outside…

From Ants to Praying Mantises

So how does this relate to praying mantises, you might reasonably wonder. It happened one day while my son was watching a video about an inside, managed ant colony during lunch. The colony owner explained that his colony was so successful that it was growing too large for the terrarium, so he was looking to introduce some predators to help control the ant population. I drifted closer to the TV as the colony owner showed off his selected predator, a striking female praying mantis. I don’t remember the species but it was not native. The colony owner carefully managed the mantis’s introduction to the colony and shared video he had taken of her first captures. I found myself sitting on the couch with my son watching to the end of the video, totally caught up in the story of this praying mantis and her fight for survival in this mini-ecosystem. The video ended and my son and I looked at each other and asked the same question: What happened to the praying mantis??

Naturally, we searched the web for answers. The praying mantis appeared briefly in only one more video, some time later, with no mention again, her fate unknown. Others had the same questions we did; we found several posts in various Reddit groups asking about her. But there was no more information. The search had sparked an interest in this species, though, so I did a little more reading about praying mantises. And discovered a serious debate about their presence, with many extolling their benefits as a garden friend and just as many condemning them as garden foes.

The Praying Mantis: A Closer Look

Praying mantises belong to the order Mantodea, characterized by their elongated bodies, triangular heads, and large, compound eyes. Their front legs, which they hold in a prayer-like position, are adapted for swiftly capturing prey. This posture not only gives them their name but also adds to their appeal. They are easily recognized, when you find them.

Fun fact: I learned during this research that mantis refers to the genus of Mantis but mantid refers to the whole group. So some sources say it is more accurate to say “praying mantid” rather than “praying mantis”. Please excuse the inaccuracy but I have mostly used the common name “praying mantis” in this post.

Diversity and Distribution of Praying Mantises

There are about 2,000 mantid species around the world, mostly in Asia, with only about 20 native to North America. Notable native species in North America include the Carolina mantis (Stagmomantis carolina) and the California mantis (Stagmomantis californica). Unfortunately, and herein lies the controversy, introduced species such as the Chinese mantis (Tenodera sinensis) and the European mantis (Mantis religiosa) have established significant populations across North America. I was surprised to learn that there are no native praying mantises in the Northeast region of the US, where I live. So all of the praying mantises I have seen, as a child in upstate New York and as an adult in Massachusetts, were not native.

Physical Characteristics

The Carolina mantis is typically pale green to tan and measures about 2 to 2.5 inches in length. The Chinese mantis, one of the largest species in North America, can reach up to 4 inches and displays a green or brown color with a distinctive stripe along its wings. The European mantis, identified by a black dot on the underside of its forelegs, ranges from yellowish-green to tan​​. The praying mantis, like all insects, has three body sections: head, thorax, and abdomen, although their abdomen is much longer than their other body sections. Most praying mantis species have wings, used for just short flights and defensive displays.

The Role of Praying Mantises in the Ecosystem

Mantises thrive in diverse habitats, including grasslands, forests, and gardens. As ambush predators, they use vegetation and environmental features to hide from prey. Praying mantises play a crucial role in controlling insect populations. Their predatory behavior helps maintain the balance of ecosystems by keeping pest populations in check.

Hunting and Feeding

Praying mantises are ambush predators, using their excellent camouflage to blend into their surroundings while they wait motionless for prey. This camouflage consists of cryptic coloring, meaning their color matches their environment, and, in some species, interesting body shapes that make the mantis look like leaves or sticks. They are such masters of camouflage that they will sometimes sway in place, looking like leaves blowing in the mind. Praying mantises also will stalk their prey, moving slowly and silently to remain undetected. They are able to rotate their heads in a very owl-like 180 degrees, enabling them to keep their prey in sight with binocular vision. Their excellent eyesight and quick reflexes allow them to capture prey with lightning-fast strikes. They also detect scent with their antennae. Their keen senses, stealth hunting method, and fast strikes make praying mantises effective natural pest controllers in gardens and agricultural fields​​, which is why you will sometimes see them marketed as natural pest control for gardens and hear of people moving wild-found egg sacs to their property.

Praying mantises are carnivorous insects, feeding mostly on other insects such as flies, crickets, grasshoppers, dragonflies, and beetles — and even other mantises. Surprisingly, there are reports of them capturing small reptiles, birds, and mammals. They are voracious hunters but they are also prey for birds, bats, reptiles, and even spiders.

Reproduction and Lifecycle

You have probably heard that the female praying mantis eats the male after mating; this shocking behavior is an example of sexual cannibalism and is thought to provide additional nutrients to the female, aiding in egg production​. Some sources say this only happens occasionally in the wild. After mating, female mantises lay egg cases called oothecae, which contain dozens to hundreds of eggs. These egg cases are often attached to twigs or other surfaces and hatch in the spring. The young mantises, or nymphs, undergo several molts before reaching adulthood. Praying mantises only live about 10-12 months.

The Controversy: Native vs. Non-Native Species

The introduction of non-native mantis species such as the Chinese and European mantises has sparked a debate among conservationists, gardeners, and entomologists. While these species were introduced to control agricultural pests, their presence has raised concerns about their impact on native mantid populations and local ecosystems​.

Ecological Impact

Non-native mantises can outcompete native species for resources, potentially leading to declines in native mantid populations. For instance, the larger size and aggressive nature of the Chinese mantis allow it to dominate over smaller native species like the Carolina mantis. Additionally, the larger size of non-native species means they can capture more and larger prey than native species; since mantises prey indiscriminately on a wide range of insects, including beneficial pollinators such as bees and butterflies, non-native species can disrupt local biodiversity and the ecological balance. There have even been reports of larger mantises preying on small vertebrates, including frogs, lizards, and hummingbirds! These incidents, although rare, raise concerns about the broader ecological impact of introduced mantis species on native fauna.

I found a fascinating study conducted by a research team from Wheaton College, MA, USA. They investigated the diet of the local mantis population in several mature fields in southeastern Massachusetts by extracting the stomach contents from captured praying mantises and subjecting the samples to DNA analysis. I admit, I shy away from imagining this process but I can appreciate the science. The researchers captured more Chinese mantis than European and found that, overall, the mantises had consumed over 270 different prey species! The two species followed different diets, even when living in the same fields, suggesting they may have found somewhat different ecological niches, perhaps based on their different sizes (the Chinese mantises being larger). Although their diets were mainly beetles, moths, grasshoppers, and spiders, concerningly, the mantises had also consumed bees, wasps, butterflies, and dragonflies. The results from this study demonstrated the incredible diversity of praying mantises’ diet which included important pollinators and natural pest predators.

Managing Mantid Populations: Ethical and Practical Considerations

Given the ecological implications of non-native mantis species, some conservationists advocate for the selective removal of these species to protect native populations. This involves identifying and destroying egg cases of non-native mantises while preserving those of native species. However, this approach requires careful consideration and knowledge to avoid unintended consequences​​.

Gardeners’ Role

Gardeners can play a crucial role in managing mantid populations by monitoring and selectively managing egg cases found in their gardens. If you find an egg case in your yard, it is often best to leave it undisturbed if it belongs to a native species. If the egg case is from a non-native species and is in a vulnerable location, call your local agricultural extension to find out what the recommendation is in your area but it’s possible you may be able to carefully relocate it to a less disturbed area. This helps ensure that the mantises can hatch and contribute to pest control without negatively impacting native species. Avoid introducing non-native species to your garden no matter how sensational the marketing is. If you are looking for effective natural pest control using native species, you may want to consider ladybugs (lady beetles) or green lacewings which consume only certain garden pests versus praying mantises which are indiscriminate hunters, meaning they will eat almost anything they can catch including helpful pollinators.

All this was a good opportunity to talk with my son about ecosystems and the role species and individual creatures play in that environment. And how we humans impact those systems, positive and negative, and the unintended consequences that can happen when we meddle even with the best of intentions. Of course, that led to a long lecture from him on the role of ants in the ecosystem and their complex social lives but I will leave that for a future blog post!

Our Celebrity Praying Mantis

Turning back to the girl who started me down this path, I must confess I held something back about the praying mantis who was introduced to the managed ant colony. At the end of the video, the colony owner wondered what to do with the praying mantis if she successfully reduced his colony’s population. He casually mentioned that perhaps he would release her in the wild. I am sure he thought this would be a kindness but this comment set off alarm bells in my brain which is why I started digging into this topic to learn more. I knew that releasing a non-native species would be problematic but I had no idea how large the population of non-native mantises is nor the impact they could have on local ecosystems. It is yet to be determined exactly how big an impact nor can we tell what will happen over time as native mantid species and their prey species adapt but certainly we don’t want to be releasing additional non-native mantises to the wild.

Embracing the Complexity of Praying Mantises

Praying mantises are remarkable insects with their unique appearance and predatory prowess. Their role in controlling pest populations makes them valuable allies in gardens and agricultural fields. However, the presence of non-native mantis species presents a complex challenge that requires careful management and consideration.

By understanding the biology, behavior, and ecological impact of praying mantises, we can appreciate their importance in our ecosystems and make informed decisions to protect native species and maintain biodiversity. Whether you are a gardener, a nature enthusiast, or a conservationist, embracing the complexity of praying mantises can lead to a deeper appreciation of these fascinating insects and their role in our natural world.

Let’s connect!

Please share, have you seen a praying mantis? When and where? What species do you think it was? I would love to hear your thoughts on the debate about native and non-native species and what you think we should do to balance these populations and their role in our local ecosystems. Comment below or visit the From Flora to Fauna Facebook page and share your thoughts (and photos!) there.

Resources

Rankin et al. (2023). Diets of two non-native praying mantids (Tenodera sinensis and Mantis religiosa) show consumption of arthropods across all ecological roles. Food Webs, 35, e00280.

explore | connect | share | transform