The Praying Mantis, a Friend and Foe of Gardens?

mantisPerplexed gardeners might suspect that the frothy, walnut-size blobs attached to shrubs, fence posts and grass stems this time of year are insect-related. But not many guess that these are the egg masses of praying mantises.

There are several species of insects in the Northeast that are collectively called praying mantises. The largest in New England, the Chinese mantis (Tenodera sinensis), is responsible for most of the big egg masses. The Carolina mantis (Stagmomantis carolina), our smallest and only native species, and the European mantis (Mantis religiosa) also deposit eggs in insulated sacs, or “oothecae.”

Brought to North America at the turn of the 20th century as predators of agricultural pests, both the Chinese and European mantises are continuously replenished when home gardeners buy mantis eggs from garden supply stores. The insects are summertime terrors, suitably adapted for capturing and devouring small insects. But the largest of them will target frogs, snakes, hummingbirds and small mammals.

Mantises are masters of camouflage, and despite their size (a Chinese mantis can grow to be four or five inches long), they can go unnoticed through the warmer months. Winter is frequently the best time to discover whether a local park or garden has a population of mantises, because their eggs are fairly conspicuous once the leaves have fallen.

Urban myths about praying mantises abound.

First, there is no fine for killing a praying mantis. Growing up in Canarsie, Brooklyn, my friends and I imagined penalties of $50 to $250 — depending on whether the murder was premeditated. A mantis found in the grill of a station wagon was an accidental death, but turning a magnifying glass on a mantis could get you the maximum sentence.

The claim that praying mantises feed on hordes of garden-destructive insects is true, but mantises are equally happy to rid your garden of beneficial pollinators, such as bees and butterflies. Mantises are also not above cannibalism. The egg case sold in catalogs will generally hatch into happy Chinese or European mantises eager to eat one another, or any native Carolina mantises nearby.

Then here is the mother of all mantis tales: The male mantis cannot copulate without the risk that the female will bite his head off. Though generally untrue, the idea is not completely without merit. The mantis’s brain coordinates motor control, but ganglia within his abdomen control copulation. So having literally lost his head, a mantis may be capable of more aggressive copulation once the tempering influence of the brain is removed. There may be more than just nutrition inspiring the female.

Studies of wild mantises indicate that a fast male won’t be a meal. In fact, most flew off after mating. Earlier studies conducted in laboratory tanks left males with nowhere to run — which may explain how more captive males met their mates and their makers together in one last wild burst of glory.

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