Mantids not best for garden

By Marianne C. Ophardt, Special to the Tri-City HeraldOctober 12, 2012 

PASCO, Wash. -- Boy, was I surprised to find a praying mantid in my hand instead of the leaf I thought I was picking up!

This fall, I've run across several mantids in the garden. "Mantid" is a broad term that refers to all members of the mantid family, and "mantis" is more specific, referring only to members of the mantis genus.

Here are the top five reasons I find mantids fascinating insects:

1. They're aliens: While there is a small (1-inch-long) gray native mantid found in our region of the state, it's rarely encountered.

The most common alien mantid in our area is the European mantid (Mantis religiosa). It came to the U.S. hitchhiking on a shipment of nursery plants sent to North America in 1899.

The European mantid is 2 to 3 inches long and bright green to tan in color. It has a black "bull's-eye" on the inside surface of its front legs.

Another common species in Washington is the Chinese mantid (Tenodera aridifolia sinensis), introduced into the United States in 1895 from China for the purpose of pest control. It's from 3 to 5 inches in length and green to brown in color. The egg cases of both species are commonly found for sale in nurseries and via mail-order.

2. They're cannibals: The primary diet of these large mantids consists of insects that come to them, including beetles, leafhoppers, flies, grasshoppers, moths, spiders and honey bees. They also will eat other mantids and their own siblings, especially right after they hatch. And while there is a general belief that female mantids eat their mates, some reports suggest that this is because investigators used starved mantids in their studies.

3. They look weird: These insects have fascinated observers for centuries because of their strange appearance. They have been given the descriptive name of "praying" because of the way their front legs fold, resembling a person with their hands folded in prayer.

While they may look like they're folded in prayer, these raptorial forelegs are what make mantids such effective killers. There are spines on the upper insides of their legs that allow them to grasp and hold onto helpless prey. Did you know that mantids usually bite the head off their victims first before consuming the rest of the body?

The mantids' heads and bulging eyes are features that makes them fearsome garden predators. Mantids can turn their head more than 180 degrees while looking for prey, plus they have two big compound eyes and three simple ones that enable them to see prey 60 feet away.

4. They blend in well: Mantids are experts at camouflage. The European and Chinese mantids are able to their change body colors (in shades of green to brown) to match the background where they're sitting.

5. They're not effective garden predators: Although mantid egg cases often are sold as a way of controlling garden pests without pesticides, mantids aren't effective predators. With only one generation each year, their population in the garden builds up quite slowly.

Instead of hunting, mantids wait for insects to come to them, so they aren't good at controlling the most common damaging pests in the garden, like caterpillars, mites and aphids.

Also, don't forget they're cannibals and will eliminate other mantids in the area competing with them for food.

* Marianne C. Ophardt is a horticulturist for Washington State University Benton County Extension.

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