Garden Dilemmas, Delights & Discoveries, Ask Mary Stone, New Jersey Garden blog

Praying Mantises Beneficial or Bad

A woman's hands holding praying mantis nests that look like dry brownish marshmallows

Hello fellow readers, While praying mantises can be beneficial, others can be bad for the garden. It largely depends on whether they are native or non-native. And, what pests you intend to target as even the native praying mantis feed on bugs that are good for your garden.

Praying mantis nests look like dried up marshmallows

Upon returning the ladybug house to my kind neighbor who offered her ladybugs to tend to my aphid dilemma, Monica showed me the nests of praying mantis she also mail ordered. They were in a small aquarium-type container sitting in her vegetable garden. Praying mantis nests look like dried up marshmallows and, unbeknownst to me if you put them to your ear, you hear a crackling sound—  I suspect the sound of baby mantises growing inside.

“Babies,” Monica texted a few weeks later, along with a photo of the cute little praying mantis poised on her basil.

Praying mantises’ behavior may overshadow the benefits in the garden.
a newborn praying mantis on oregeno leaf

Baby Praying Mantis / Photo compliments of Monica

It’s remarkable how a newborn praying mantis looks like a miniature grownup one, unlike most critters. But as I learn more about this fascinating creature, the queasiness over their behavior seems to overshadow the benefits they serve in the garden.

Maybe you’ve heard how females often eat the heads of the males after mating. They then lay their egg sacks on twigs, fences, siding, or other structures before they die in the fall after the first frost. A female lays about 300 eggs in frothy liquid excrement that then solidifies. Only a fifth of the eggs will survive to adulthood. If you purchase nests to hatch at home, its best to buy them when it is warm enough to release them right away; otherwise, they emerge famished and are known to eat one another if they can’t find food quickly.

While praying mantises can be beneficial, they also eat beneficial bugs.

While the native Carolina praying mantis (Stagmomantis carolina) are considered beneficial controlling pests such as mosquitoes, flies, and crickets, they also eat beneficial bugs. So, it’s best to identify your target pests before considering them as biological controls.

The population of the native praying mantis is lessening due to introduced species such as the invasive Chinese mantis. Tenodera sinensis, native to Asia, are sold as pets. They say a nurseryperson near Philadelphia mistakenly introduced them here in 1896. They’re over four inches long versus the native species, which only grow to two to two-and-a-half inches.

Non-native praying mantis feed on native mantises, toads, and hummingbirds

Both the native and non-native praying mantis vary from greyish to brownish to green, adjusting with each molting to blend with their environment. The Chinese mantis shares the same appetite as the native ones but also feed on monarch butterflies, small reptiles such as toads, and little frogs, even hummingbirds. They also eat the native praying mantis. Then there’s the European mantis (Mantis religiosa), a bit smaller than the Chinese mantis brought here to feed on the gypsy moth caterpillar. They, too, are now considered invasive.

Sadly sources are selling non-native praying mantis as biological controls.

Even credible sources are selling non-native praying mantis as biological controls. Maybe they don’t know the detriment they are causing the native populations. So be sure to shop for praying mantis native to your area by using the scientific name. Or, perhaps better yet, let Mother Nature decide if they should be in your garden. Garden Dilemmas? AskMaryStone@gmail.com (and now on your favorite Podcast App.

Click through to the previous column about Monica’s Beneficial Ladybugs. 

Link to New Jersey Audobon’s column on Praying Mantis – Indiscriminate Predator

Mary Stone, owner of Stone Associates Landscape Design & Consulting. As a Landscape Designer, I am grateful for the joy of helping others beautify their surroundings which often leads to sharing encouragement and life experiences. These relationships inspired my weekly column published in THE PRESS, 'Garden Dilemmas? Ask Mary', began in 2012. I dream of growing the evolving community of readers into an interactive forum to share encouragement and support in Garden and Personal Recoveries - seeking nature’s inspirations, stimulating growth, weeding undesirables, embracing the unexpected. Thank you for visiting! Mary

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