Praying Mantids: The Good, The Bad, The . . . Interesting

In my role as Extension entomologist, I recently participated in a couple of programs in Madison where the subject of praying mantids was raised. The first program was a gardening expo where I tended a Good Bug/Bad Bug Booth. A very enthusiastic and knowledgeable gardener approached me with an air of purpose about her, and proceeded to tell me that she was going to try praying mantids "one more time". This gardener had been purchasing mantid egg cases for a couple of years, and hanging them in the shrubbery around the garden. She had never once seen a mantid; and upon examining the egg cases, had never seen one with holes from which the "babies" might have hatched. I discussed several possibilities with her, but finally I had to end with, "But, you know, praying mantids don't really provide much help with pest control; you might want to invest in more effective beneficials." To which I received the very knowing reply, "Oh, I know they don't help. I just think they're interesting, and I wanted to be able to show them to my kids!"

The second program was for a group of commercial greenhouse flower growers. We were hosted by a grower who produces certified organic herbs. She explained that her pest management was based largely on biological controls. She proceeded to tell us what worked and what didn't. In the "didn't work" category were birds (messy), chameleons (too scary for the customers), and praying mantids. The problems with mantids were multiple: there were never enough to do much good; they ate some of the other beneficials; they tended to "bite the heads off" of their siblings; and they "reared up and hissed" at the customers. Needless to say, they were no longer a part of this particular pest management program.

These two true stories are what prompted the title of this article. First, "the good". Mantids are beneficial to the extent that spiders are beneficial. They do prey on pests; but they do represent the extreme "generalist" in the world of predatory insects. Which leads to "the bad". Mantids will eat virtually anything they can catch, including their siblings and other beneficials. Large mantids, such as the commercially available Chinese mantid, will even catch and eat bees and other pollinators. But finally, "the interesting". The family of insects known as Mantidae is large, and there are many fascinating, peculiar, even bizarre mantids in the world. Because of their large size, large and seemingly inquisitive eyes, and their "praying" stance, we as humans seem to be able to identify with them. They can be useful subjects to teach about nature and its various mechanisms of balance. They can be a wonder to children. If you find them in your garden, appreciate them as components of nature. If you wish to purchase them, do so as a source of education or interest. Just don't expect that they will provide much benefit in pest management.

- Dan Mahr, University of Wisconsin

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