One of the few signs of insect life to be seen in the winter are egg cases, like the oothecae of mantids.
The chunky, squared-off oothecae of Chinese mantids are particularly easy to spot long after leaves have fallen, affixed to twigs and small branches. Each can contain hundreds of eggs, though both cannibalism of siblings upon hatching as well as the general dangers any tiny insect faces in the world whittles down significantly the number who reach adulthood.
In recent years, more and more gardeners and native plant aficionados have been suggesting removing and destroying the crunchy-looking cases when encountered. Their contents are considered unwelcome non-natives with a nasty habit of mercilessly and indiscriminately devouring other insects, beneficial or not: bumble bees, butterflies, moths, and even the occasional unfortunate vertebrate, including hummingbirds, may become a meal.
Our smaller native Carolina mantis may also suffer at the raptorial forelegs of its cousin; not only can the Chinese mantis — almost twice as big as the Carolina mantis — outcompete it for prey, the smaller mantis can also itself become prey for the larger.
But the jury seems to be out on the extent of the harm caused by the Chinese mantis. It was introduced onto this continent more than a century ago, and has naturalized across much of the U.S., particularly in the eastern states without devastating effects thus far. Given the many other dangers little Carolina mantids and beneficial insects in general face from us, including habitat loss and pesticide use, we might consider leaving the oothecae and working to make our world more hospitable to all our insect friends.
Chinese mantids and their egg cases have nothing to fear from me, at least. I still think they're neat.
Resources/Additional Reading
- Missouri Department of Conservation: Chinese Mantis
- Challenging the Conventional Wisdom About Praying Mantids (NC Extension). Includes some great photos showing the inside of oothecae, with an anti-Chinese mantid perspective.
- Iowa State University Extension & Outreach: Praying Mantis
- Wisconsin Horticulture: Praying Mantids
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