Friend or Foe?


Most of my life I have believed that Praying Mantises are natural beneficial insects for our gardens and environment. But are they really? I would even suggest we begin, as I have, treating them as an invasive species. Now hear me out before you go calling me crazy.
First of all, we do not have any “native” Mantis species in Michigan, the closet is the Carolina Mantis which is native south of Michigan and has been recorded on a few occasions mostly in the southeast part of the state. This North American native is only about 2 inches long and likely does no harm to our native insect populations. The egg case is small and narrow with two lines visible on it.
Next, we have the mantis that I grew up with thinking it belonged here but later found that it was actually the European Mantis and native to Europe. This species is about an inch longer than the Carolina Mantis and may have a minor impact on our native insects. The European egg case is a bit bigger but still long and somewhat narrow, it is shown on the left in accompanying photo.
Finally, we have my nemeses mantis, the large Chinese Mantis that was introduced from China in 1896 to combat pests. It has been and is being sold as a beneficial insect control for pests in your garden. This species is the largest in North America coming in at about 5 inches long, give or take a bit. They are voracious eaters, devouring almost everything that moves in front of them. If handled incorrectly they will attempt to bite and can give a painful pinch to the hand holding it. They are known to eat almost anything that comes before them including insects of all types, hummingbirds, insect pollinators, butterflies, small reptiles and amphibians. One that we captured this past some on a Prairie walk at the Hudsonville Nature Center was eating a honey bee. This mantis lays not just one, but can lay two or more egg cases each year. The egg case is shorter and larger around than the other two species making it easy to identify, it is pictured on the right in the accompanying photo.
At the Hudsonville Nature Center, we have a six-acre planted prairie. In the past it has been occupied by many pollinator and butterfly species. A few years ago, I noticed the decline in the presence and numbers of both species and individuals of the many species of not only the pollinators and butterflies, but insect in general in this parcel. Then while walking through this prairie the end of March 2018, I began to find a large number of Chinese egg cases. That afternoon I collected over 100 egg cases in the six acres. Many were attached to woody stems and higher up from the ground than the few European ones I found that day. I collected all that I found and removed them. This past summer the butterflies are returning and the other pollinators are slowly being seen again.
So, I ask you is the Chinese Mantis a friend or foe in our Michigan ecosystems? Personally, I go so far as to call them an invasive species causing much harm.

Left: European, Right: Chinese

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