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Praying Mantis: Garden Friend? Or Fiend?


Praying Mantis: Garden Friend? Or Fiend?

Q. Linda in Pennington New Jersey originally wrote: "I found some galls on my butterfly bush and spice bushes. Are they good, bad or what? They are the size of a cherry tomato and have a glossy coat. I would like to know what they are; and if I should destroy them? Or be glad I have them."

A. To which I replied, "they're praying mantis egg cases; be happy you have them!"

Q: A few days later, Linda wrote back: "When you said praying mantis egg cases I was happy; but my daughter sent me a link to a Facebook page that identified them as non-native Chinese praying mantis egg cases. The Chinese praying mantis consumes native pollinators, butterflies and native mantises. So now I'm going on a hunt to get rid of them."

A. Linda--that was YOUR email on OUR Facebook page! The photo you sent of the egg case was great, and the post itself created a storm of controversy; 133 'likes' and 25 comments, which ranged from 'destroy them all!' to 'don't kill any of them'! So before we delve into this, I hereby submit my personal definition of the three types of garden insects:
    • Beneficial insect: one that ONLY eats garden pests, often a very specific pest, like green lacewings feeding on aphids.

    • Predator: Will eat anything it can catch. A good example outside of our mantis topic is the large group of 'mini wasps' that lay their eggs inside of caterpillars. They could target a larval butterfly instead of as a nasty pest like the tomato hornworm. Same as spiders; they eat anything they can catch. Both are welcome defenders in my garden.

    • Pest insects: The ones in your garden right now.
Although often touted as beneficial, the various groups of mantises around the world are all predators like spiders. But nobody I know buys mail-order spiders, while a lot of gardeners DO buy mantis egg cases, which may contain eggs of the larger and hardier Chinese variety. (Which have been imported for pest control for well over a hundred years.) At the far extreme, other gardeners seek out and actively destroy the egg clusters of the Chinese mantis. Some say it's because they are endangering the smaller Native American 'Carolina Mantis.' Others note that the Chinese mantis has been known to prey on hummingbirds, native bees, butterflies and small amphibians.

Guess what? So will any other mantis species if they get the chance. Not to mention that they all eat other members of their own species, especially the female, whose (hopefully) unique post-courtship behavior can make males as scarce around town as a free viewing of the film "Fatal Attraction".

Moving on, let's review the three different species you might find in your garden, beginning with the one rarely mentioned.
    • The European mantis. Said to have arrived on our shores in a shipment of plants in 1899, this 'Old World Mantis' (Mantis religiosa) receives only praise from the University of Delaware's celebrated "Bug Man", Dr. Michael Rapp, who notes that these Europeans seem to have a distinct appetite for the nasty stink bug! He also notes that, in his garden, they love to eat the milkweed bug that ravages the only host plant for monarch butterfly babies, but they leave the monarch caterpillars alone. The European mantis is widespread on the East Coast and up into Canada, around three inches long (the female is slightly larger) and comes in a vast array of different colors.

    (Note: The Brandywine Conservancy, who have issued what is probably the biggest thumbs down on Asian manti), is the only source I could find that says that the European mantis was deliberately introduced to control gypsy moth caterpillars and that it was the Chinese variety that came here accidentally. Go figure.)

    • We move on to the other non-native species, the dreaded Chinese Mantis! (Tenodera aridifolia). Despite being described by non-fans as only slightly smaller than Godzilla, the females (always bigger than males) are about four inches long. While the Conservancy disagrees, it seems highly likely that they were imported here as pest control. Yes, they will eat teeny tiny little birds, but big birds love to eat THEM, as do bats when the manti fly by night.

    • And finally we have our very own 'Carolina Mantis' (Stagmomantis Carolina), so named because it was first seen in the Carolinas, but is now found almost everywhere in the continental US, Canada and South to Brazil. (It is also the official state insect of South Carolina.) It is slightly smaller than the others at two and a half inches long, and changes color when it molts to try and match the colors in its hunting ground.
And now: DRUM ROLL! The really BIG news: The Carolina mantis is NOT an endangered species. Nor is it 'threatened'. In fact, none of the roughly 200 species of mantis found in North America are in any kind of trouble; (they are alpha predators, after all). Despite many hours of searching, I could find no evidence that our scrappy little native guys are being devoured to extinction by giant Asian menaces; just hearsay and cage rattling from people who perhaps watched too many Kaiju movies.

So you probably know where I stand on this issue. As with spiders, I enjoy the presence of mantises in my garden even though they are predators. And while I do urge you to read up on these fascinating creatures, do so with a few grains of salt when you come across mantis-shamers.

As with the fabulous Japanese honeysuckle, too many gardeners and organizations tend to make lists of insects and plants they want you to destroy, but that many of us enjoy. For my money, this kind of activity is way too close to other lists of 'bad and good' things that our past should warn us not to make.

And gardens should be about life, not death.

Oh--and it turns out that CAROLINA mantis egg cases are widely available for sale. If you think they really are in trouble, raise a batch and even the odds!~

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