I made a new friend the other day in Indiana! It’s a little praying mantis friend 🙂
There are around 2,400 known species of mantids (Mantidae). These large, slow-moving insects are typically found in tropical and subtropical regions. They are found on all continents except Antarctica. Mantids are easily recognizable from the enlarged upper portion of their front legs.
There are only 20 species of mantids that you can find in the United States. Of those, only three can be found in the Midwest where I was. While I would have loved to see the native Carolina mantis (Stagmomantis carolina), the reality is that I found a Chinese mantis (Tenodera airdifolia). If you find a mantid in your backyard, chances are it will also be a Chinese mantis. The Chinese mantis is larger than the Carolina mantis and has been able to outcompete the Carolina mantis for food.
Some quick name facts
You might have noticed me using ‘mantid’ instead of ‘mantis.’ Don’t worry; it’s not a typo! The term ‘mantid’ refers to any species within the family Mantidae. ‘Mantis’ is technically the term for a specific genus of mantids. So, just like all squares are rectangles but not all rectangles are squares, all mantises are mantids, but not all mantids are mantises.
The terms ‘mantid’ and ‘mantis’ reflect mantids’ pious posture and their supposed supernatural powers. Their name comes from ancient Greek: ‘mantis’ means ‘diviner,’ and ‘mantid’ means ‘soothsayer.’ The term ‘praying’ is also a nod to religion – praying mantids hold their forelegs as if praying!
If you’ve heard about praying mantids, you’ve probably heard that males are smaller than females and that females will eat their partners during sex. But while praying mantids do partake in sexual cannibalism, they don’t do it nearly as often as you may think. For starters, not all mantid species practice sexual cannibalism.
In addition, females eat their mates only about 30% of the time. Males are only really in trouble if the female is particularly hungry. The hungrier the female, the more likely she’ll eat her mate. This makes sense, as creating and laying eggs takes a lot of energy; a male represents a convenient food source. Female mantids that cannibalize their mates may produce significantly more eggs than those that don’t.
“But doesn’t eating your partner mean your eggs won’t get fertilized?” Don’t worry. Praying mantids have a solution for this problem! During mating, the male will mount the female from behind. If the female feels hungry, she’ll turn around and bite off the male’s head. But the male’s body doesn’t know its head is gone, so it keeps mating with the female. This can sometimes go on for hours until the body finally dies or the female consumes it all.
And don’t worry, this sexual cannibalism may benefit the male, too. By having his body inside the female and blocking her reproductive tract, a male can successfully stop other males from mating with the female. This increases the chances that the offspring will be his. This is important since he won’t get another chance to fertilize any other eggs!
Praying mantids are ambush predators. They slowly stalk or ambush their prey, relying on impressive camouflage to get close. A praying mantid’s coloration depends on its environment: European praying mantises are green or brown to blend in with the native plants, while orchid mantises are colored to look like a flower. Praying mantids sometimes even sway slightly to better mimic a leaf or flower moving in the breeze.
Praying mantids eat exclusively living prey but are otherwise generalists and eat whatever comes along. For the smaller mantids, this usually means insects, but larger praying mantids can catch and eat small birds and mammals.
Praying mantids typically wait silently until their target walks by. Then, they strike with their forelegs in an attack that takes only milliseconds. The spines of their forelegs are interlocking to keep prey captured; sometimes, the target even ends up impaled.
Praying mantids succeed in ambush hunting in part because they have excellent eyesight. For starters, praying mantids are the only insect that can swivel their head 180 degrees. This is due to a flexible joint between the head and the thorax.
They’re also the only invertebrate (that we know of) that can see in 3-D. Seeing depth likely helps praying mantids accurately calculate where and when to strike when catching their food.
This discovery happened relatively recently (2016). For most of history, humans have usually assumed that invertebrates couldn’t see in 3-D because of their simple nervous system. However, the exceptional hunting ability of praying mantids suggested they could see in 3-D, prompting a group of enterprising scientists to outfit African praying mantises with tiny 3-D glasses and had African praying mantises!
After affixing little blue and green lenses to a mantid’s eye with beeswax, the researchers showed it a ‘movie’ of bugs moving around. The mantises weren’t fooled when the movie was in 2-D, and they didn’t bother trying to catch them. But when the movie was played in 3-D, the mantises struck at the screen to try to catch the bugs. This suggests that mantids do indeed use 3-D vision when they’re hunting.
Even though they can see in three dimensions, praying mantids don’t see like us. Their eyes are made of two compound eyes and three small, simple eyes that only see light and movement (called ocelli). With their ocelli, praying mantids can detect motion from 60 feet away.
Why do we care about mantid vision? Because knowing how an animal with such a simple nervous may help us make tiny, energy-efficient robots in the future. After all, praying mantids prove you don’t need that much processing power to have accurate vision!