If you’re the kind of gardener who hopes to find predatory insects among your plants and flowers, be careful what you wish for when it comes to praying mantises. They eat good bugs as well as bad bugs.
But bugs aren’t the only things they eat. Mantids are agile, sit-and-wait indiscriminate predators that can strike with such lightning-like quickness that they’ve even been known to snatch an unsuspecting hummingbird. However, you shouldn’t be overly alarmed about witnessing such an attack if you are someone who enjoys watching the antics of hummingbirds fighting for the rights to a feeder. "I would not call mantids eating hummingbirds a common occurrence," said John Abbott, chief curator and director of Museum Research and Collections at the University of Alabama.
When it does happen, he said, it tends to occur at feeders rather than when the birds are hovering over a flowering plant. "I think in a natural situation, it would be much more difficult for a praying mantis to grab a hummingbird, not that it can’t happen. It’s just that a hummingbird is going to be a little more on its guard and tougher to catch in a natural setting, whereas if you have a feeder with several hummingbirds coming in they become pre-occupied with battling themselves and not paying attention to what’s around them. Then a praying mantis crawls up and finds a good perch, and I think this more-often-than-not is where they are able to grab a hummingbird."
Mantids feeding on hummers or even some small songbirds is such a rare occurrence that Abbott doesn’t think they deserve such a bad rap for being indiscriminate predators. "My guess is they probably end up capturing more pest insects than beneficial ones," he said.
Also on the positive side: you can never blame holes in plant leaves on them. They don’t feed on vegetation, only live prey — which can include an occasional frog or lizard. Because they don’t eat plants, there isn’t a particular plant or group of plants to include in your garden to attract them. What mantids are looking for is a favorable ecosystem that creates a habitat for insects and offers the mantids places to hide and hunt. "Just create a natural heterogeneous robust garden, and those plants will be attractive to a mantid," explained Abbott.
Be aware, though, that a praying mantis can be hard to spot. Abbott attributes that to two things: camouflage and cryptic behavior. "They can blend in quite well and then wait in a carefully positioned spot for a prey item to come by. That means that you are not going to easily notice them, either. But praying mantises are certainly not rare."
Before you go out into your garden looking for these fascinating insects, here are a few facts about them that will make observing them even more interesting.
Praying mantises are related to cockroaches
In fact, they are essentially predatory roaches, said Abbott. This is a point he says he always tries to make with visitors to the University of Alabama museum in Tuscaloosa. He finds their reactions interesting, recalling one group that was fascinated by scorpions and tarantulas but freaked out by cockroaches, which he called harmless. "You can see morphologically how similar they are," said Abbott of the resemblance of praying mantises and roaches. "A lot of (mantids) have these big broad pronotal shields, which are very reminiscent of a roach." Their heads are very similar looking. They are very closely related. "For a long time now, people have recognized similarities between roaches and mantids and even termites," said Abbott. "But, it was not until molecules confirmed a lot of those relationships the entomological community overall has accepted that. These days roaches and termites are now put in the same order. They used to be in a different order. Historically, at times, people would use the order Dictyopera to put roaches and mantids together. I suspect it won’t be a year or two until somebody does some more analysis and proposes that roaches, mantids and termites all go in the same order. So, basically, you can think of termites as social roaches and praying mantises as predatory roaches."
Those praying arms are dangerously deceptive
In fact, the arms of praying mantises are deadly weapons called raptorial forelegs. The mantids attack their prey by suddenly elongating and jutting out their folded-up forelegs, which are actually fairly long segments. Spines on these predatory forelegs help them hold onto their victims. Mantids are one of a few groups of insects that have forelegs that are especially adapted for capturing prey, explained Abbott. Rather than just letting them dangle, mantids fold them up in a way that gives the impression of a prayerful pose, which is, of course, how they got their name.
Sex can be risky for males, but the reason is often misunderstood
One study concluded that females may decapitate males about 15 percent of the time when they mate. One of the reasons given for this that has even appeared in old science textbooks, said Abbott, was that this was thought to be an obligatory mechanism by which severing the male’s head caused his muscles to contract and forced him to ejaculate sperm and transfer it to the female. "That’s not true," said Abbott. "It is not necessary for the male to lose his life in order to mate with the female. While 15 percent is not insignificant, that’s not the most common occurrence." What is happening, he said, is that these are pretty indiscriminate predators and the females are often larger than the males. One of the things he said that helps to explain this type of behavior from an evolutionary perspective is that being eaten as a result of having sex is an investment on the part of the male. "If the male gets eaten while mating, then you can think about it as he is basically providing nutrients for the female to gestate the eggs. Thus, it is advantageous in that sense for the male to lose his life because by doing that he is providing a nutritional resource that gives those eggs — and thus his genes — a better chance of survival. This happens in other groups, and that’s one idea behind why there is such a high percentage of females eating males."
Praying mantises only have one ear
Abbott remembers a Trivial Pursuit question decades ago that he still chuckles about … what is the only insect that has a single ear? The answer, of course, is the praying mantis. Normally insects have ears on each side of the thorax, said Abbott. But, in mantids their tympana, or ear, is merged into a singular structure and is located on the underside of their body between their legs.
Mantids have a strange body shape for a reason
They have basically evolved to be good predators, said Abbott. In addition to the raptorial forelegs, they are capable of turning their head almost 180 degrees so they can see back over their shoulder, which helps make them agile predators and also helps them escape predators. In fact, the elongated body form of the thorax is clearly an advantageous body form for a predator. It's worth nothing that here’s another group of insects not related to praying mantises called mantisflies that have a superficially similar look to praying mantises. "That’s why they get their name, mantisflies, and they are predators as well," said Abbott. "It’s convergence that these things look alike. So, it’s obviously a useful predatory form to have. They are smaller, and most people wouldn’t recognize the difference. They are common, but it’s not a group most people are going to be familiar with."
Mantids are found throughout the U.S.
There are about 2,300 mantid species worldwide, with the greatest diversity occurring in the tropics of both the Eastern and Western Hemispheres However, relatively few of these, about 20, occur in North America compared to their overall numbers. Even so, mantids can be found across the United States, with the greatest diversity in the South and East because they are a tropical-related group.
Mantids can go from predator to prey
While it‘s not common, mantids can prey on lizards and frogs in addition to birds. What’s more common, said Abbott, is lizards and frogs preying on mantids. Other creatures that prey on mantids include spiders, insectivorous birds and even bats.
Mantids might be confused with walking stick
One species of praying mantis, Brunner's Mantis (Brunneria borealis), looks like a walking stick, said Abbott. "It is really long and has no wings but it has those raptorial forelegs and that distinctive mantid head. If you look closely you’ll say, 'Oh yeah, I see those.' But, superficially, at a glance, it will very much look like a walking stick. All of the walking sticks in the United States except one species in Florida, Mayer's Walkingstick (Haplopus scabricollis), which has short wings, are wingless." The key ways to the difference between a praying mantis and a walking stick are that praying mantises have the predatory forelegs (walking sticks do not because they are vegetarians and don’t need them) and the triangular head that is distinctive of a mantid.
Mantids overwinter by producing an egg case called an ootheca
The adults can’t survive freezing temperatures, but in cold-weather climates, they ensure the survival of their species by laying hundreds of eggs that are essentially glued together in an egg case called an ootheca. "Basically, roaches do the same thing, and it’s another example of how they are similar," said Abbott. "You can often determine the presence and the species of a mantid in your garden (even if you don’t see it) from their ootheca because the ootheca are fairly species-specific in shape and appearance," said Abbott.
Females frequently will wrap the egg cases around something thin such as a tree limb or twig or a fence wire. Sometimes you’ll even see them attached to the sides of houses. As with many insects, the egg case often contains hundreds of eggs because only a few of the eggs will ever become mature mantids. For one thing, not all the eggs will hatch. For another, wasps will sometimes prey on the eggs. The majority of the eggs that do hatch will become prey for other insects, and sometimes even brothers and sisters will kill and eat each other. Sometimes garden centers or online vendors will offer ootheca for sale, but Abbott urged caution in purchasing these. "There’s nothing wrong with that I suppose, as long as the species you are putting into your garden is naturally found in your area. You have to be careful that you are not introducing a species into an area where it shouldn’t belong. That’s always a hazard with such activities."