You may have noticed some large, charismatic insect friends hanging out in tall grasses or low bushes lately, or perhaps absorbing the warmth of the sun on the side of a building.
Late summer and early fall is prime time for seeing praying mantises. The adults have finished mating and the females are out and about laying their egg cases, known as oothecae. As winter approaches, the adults will die and their oothecae will be left behind to overwinter, awaiting the warmth and moisture that comes with spring. At that point the conditions will be right and eggs will hatch. Somewhere around 100 to 200 nymphs will emerge from the ootheca, and this next generation will disperse amongst the grasses and shrubs that will be their home for the next several months.
European mantis in green coloration. Photo by eLKayPics, licensed via Creative Commons.
In Massachusetts there are two species of praying mantises, the Chinese mantis, Tenodera aridifolia, and the European mantis, Mantis religiosa. As you can guess from their common names, neither of these insects is native to North America. Both species were introduced over 100 years ago, likely by gardeners looking to control pests.
Here at the Hitchcock Center we’ve seen our fair share of mantises. One difference between the two is their size. Chinese mantises are the largest mantis species among more than 20 found on our continent, reaching 11 centimeters (4.3 inches) when full grown. European mantises reach 7 cm as adults. In both species, females grow 1 to 2 cm longer than males, and are less agile but more physically powerful. Another difference between the European and Chinese mantis is the patterning on the head. Chinese mantises have vertical stripes on their faces whereas the faces of European mantises lack stripes.
Individuals of both species come in green and brown types, or morphs. Once, when some students in a Hitchcock homeschool program were observing a brown European mantis sunning itself on the side of our building, the students speculated on why some mantises were green and others were brown. No one (including the teachers!) knew the answer, although several great hypotheses were suggested.
This question of why some mantises were brown and some were green has been an open topic of research at least throughout the 20th century, with lots of hypotheses suggested but until recently no good evidence to support one idea over the others. A popular explanation was that the morph color was camouflage. Others observed that individual mantises could change from green to brown, or vice versa, after they molted their exoskeleton, and that the switch seemed to be associated with changes in the temperature and humidity of their environment. The answer, it turns out, seems to be a little of all of the above.
My curiosity about this led me to a 2010 paper in the Bulletin of Insectology by Roberto Battiston and Paolo Fontana titled “Colour change and habitat preferences in Mantis religiosa.” The authors studied European mantises in northern Italy and recorded data relevant to their coloration and habitat preferences.
European mantis in brown coloration. Photo by liesvanrompaey, licensed via Creative Commons.
Battiston and Fontana observed that the proportion of mantises they found that were brown was higher during the hot summer months, when the grasses the mantises preferred to live on were a yellowish-ochre color and the thorny bushes they liked were brown. After the first autumnal rain, when the same vegetation was greenish, a higher proportion of mantises caught were green.
They also raised several European mantises in the lab. This gave them the opportunity to directly control the background color the mantises were living on. The captive mantises were kept on brown sticks and dirt, and displayed green tones by the end of autumn, but less intense greens than those seen in wild individuals, and the entire body didn’t always change.
The authors concluded that the hot sun, low humidity and intense light of the Italian summer promoted the production of both brown ground vegetation and brown mantises. More moderate temperatures, higher humidity and low light intensity promoted green vegetation and mantises. In other words, climatic variables are a causal factor in mantis color change. But while sunlight and humidity can trigger a praying mantis to shift its color after a molt, this adaptation is likely a response to predation pressures. A brown mantis during the green summer (or a green mantis during the brownish fall) would be easier for a visual daytime predator like a bird to see.
Climate, plant color and hungry predators are all factors interacting and resulting in a brown or a green mantis. Through the observation of one insect we get a glimpse into the dynamic relationship of variables that are constantly interacting and influencing one another in our world. This question of mantis color can open our eyes to the immense complexity of the interconnected web of life that we’re a part of.
This study provides good support for the concealing-coloration hypothesis for mantis color change, along with good evidence for climatic variables contributing to the change. I wonder if we would find the same patterns in mantis coloration if we repeated the study here in Amherst? Have you seen any mantises this summer and fall, and if so, were they green or brown?
Patrick O’Roark is an environmental educator and live animal caretaker for the teaching animals at Hitchcock Center for the Environment.
Earth Matters, written by staff and associates of the Hitchcock Center for the Environment at 845 West St., Amherst, appears every other week in the Daily Hampshire Gazette. For more information, call 413-256-6006, or write to us.
I saw a brown mantis in my yard in Boston but it’s body was slender and arched, and it looked exactly like a grass-like mantis. Could some have migrated north due to climate warming?
Haverhill, MA. Brown and green Chinese Mantis spotted. I have a nice picture which shows it’s pretty face if you’d like to see
Heey i live in haverhill too! Saw one a couple weeks ago amazing!
We saw a green praying mantis in our yard in Plymouth, MA
I’m in Hampstead, North Carolina. My 5 year and I found green and more brownish mantis. I enjoyed your article. Thank you. I am learning as well as teaching her with this remote learning day .
Dziękuje za ciekawy artykuł. Mieszkam na południu Massachusetts , w Webster i wczoraj znalazłam modliszkę w basenie. Wydawało się, ze nie żyje- nie wiem jak długo była w wodzie. Po godzinie czasu okazało się, ze modliszka rusza się. Nie odeszła , chodzi po stole przy grillu – na zewnątrz domu.
I have had one living on my holly bushes since September 12 in Taunton. I saw him yesterday 10/15/20. I’m amazed he’s still alive!
A beautiful green mantis is living in my window box that is full of variety of grasses. I’d love to bring him inside for the winter, alas…
Can I upload images if the mantis to your website? TY Tricia
I have a pic of my brown mantis..saw 10/13/2031 @245pm Lowell Massachsetts 01852
I’ve seen both green & brown praying mantis. Today October 22, 2021 I spotted a brown one on my deck! So cool looking love how they turn their head to look right @ you !
Winchester, MA
We’re in Northern NJ. Haven’t seen one for two years but on a run I just saw two smaller brown ones, in the road. What’s up with that?
One in my yard….brown this week.
I’ve had 3 sightings of a brown mantis with green ”under wings”, and a striped triangular head. It took up residence in a butterfly bush for about 10 days at the end of September. On October 2 it was feeding on a Raspberry bush that I was trimming. It was able to get to a nearby fence where I photographed him turning its head to look right at me… just a little eerie! A week later I “ran” into it on the driveway. I scooted it on to the grass hoping it would make it to the other butterfly bush. I was stunned by its size and its ability to maneuver on those thread-like legs.