Praying, or just preying?

Gardeners wonder about those wads of what looks like brown styrofoam that you notice attached to stems and branches, usually once the leaves fall in autumn. They stick there all winter until the first unseasonably hot weather, when hundreds of perfect, miniscule praying mantids crawl out of their egg sac in a single file.

After a warm day last week, the Praying Mantids hatched in my garden. Now there are hundreds of them, crawling on the grass, resting in the shrubbery, poised stationary on the side of the house, and struggling in vain in spider webs. They’re so tiny that it hurts my eyes to look for them, but if I can spot one there are usually more nearby. Over the next few months they’ll grow to become the largest insect in the garden, then die off when the cold weather hits in November.

Praying mantids are commonly sold along with ladybugs as beneficial insects, but I have my reservations. While the ladybug only eats insects like aphids that suck plant juices, a mantis is a totally indiscriminate carnivore. As a youngster it devours a lot of small insects that parasitize plants, but I’ve observed that as it gets bigger, its prey is often the large insects we’re trying to attract to our gardens, such as butterflies and other pollinators. Last summer I watched a praying mantis catch a honeybee, rip off its top half and toss it away, then dig in to the rest like we would eat a carton of popcorn at the movies. All that was needed was a tiny screen and a theater seat, since it looked like he was already wearing the 3-D glasses.

Although there is a Carolina Mantis (the state insect of South Carolina, in case you wondered) the mantids common in our area are usually not native, but one of two species introduced decades ago from Europe and China for insect control. This begs the question of whether these insects, interesting as they are, could really be considered beneficial. They haven’t co-evolved to share habitat with larger native beneficials like bees, butterflies, and moths. And I’ve noticed that each year I seem to be hosting more Praying Mantids and fewer butterflies at my garden parties. 

It’s hard not to admire an insect that can turn its head; compared to other bugs it almost looks human. While I can’t entirely endorse the Praying Mantis, it’s too cool to reject either. So I’ll continue to watch these creatures grow throughout the summer, until the uneasy day when I catch a four-inch long mantis ripping out a swallowtail butterfly’s thorax. Then the debate will reopen.