Predators in your Garden
by Howard Youth
Do mantids lurk in your backyard? There's a good chance they do, though you may not usually see them. Like the other 2,000 or so species found in other parts of the world, Washington's mantids are masters of disguise. The four local species range from green to tan in color, matching surrounding foliage and twigs. This camouflage serves two purposes: It hides mantids from their many daytime predators, mainly birds, and it allows them to approach and ambush prey.
Most gardeners welcome mantids as beneficial insects, thinking that they spend their lives feasting on pests. But this common belief is not completely true. "They are generalized predators," says David Nickle, a research entomologist at the USDA's Systematic Entomology Laboratory. "They feed on any kind of prey they can get their hands on--and they don't differentiate between good and bad." Nonetheless, local mantid diets include such common garden pests as cabbage butterflies, Japanese beetles, flies, and caterpillars. Mantids may also take the occasional bee or katydid.
Young nymph mantids hatch each spring from egg cases left by their mothers the previous year. Tiny young mantids emerge en masse and spread out, often helped by strong winds that carry them far and wide. By mid-summer, you can find adults and large nymphs (mantids grow to adult size in a series of growth spurts called nymphal stages or instars). By early fall, the females lay their eggs in protective, foam-like cases on plant stems or branches that sit above where snow would normally pile. The first frosts kill off the adults, and in spring the cycle starts anew.
So what's the best way to find your elusive backyard mantids? "Go out at night with a flashlight," is Nickle's recommendation. At night, mantids are much more active, mating, laying eggs, and moving around on top of the vegetation while their diurnal predators sleep.
To encourage mantids to lay eggs and hunt in your yard, you need to provide a stable environment for them. This means growing plenty of foliage that is not regularly mowed or cut, and not using pesticides. Vegetation needs to be dense enough to shelter mantids from birds, and stems and branches with egg cases should be left uncut for the winter.
Three of the Washington area's four mantids are introduced: the European (Mantis religiosa), the narrow-winged (Tenodera angustipennis), and the Chinese (Tenodera aridifolia). The Carolina mantid (Stagmomantis carolina) is native, ranging from our area south and west to California and Mexico.
You can sort out the mantids you find by following these pointers. The Chinese mantid grows the largest--up to five inches long from its head to the tip of its wings (about an inch or more longer than the others). A good fieldmark is the lime-green fore wing, which contrasts with the rest of the wing, which is tan or darker green. The narrow-winged mantid resembles the Chinese, but is slightly smaller (the hind wing of this mantid is narrower from front to rear than in the Chinese, but this can only be differentiated upon close inspection).
The European mantid can be green or tan, but it lacks the Chinese's bright fore wing. In addition, under its belly, or abdomen, you'll find dark cross bands. (Caution: Handle mantids with care--large ones can give you a sharp pinch if they strike at your hand.) The native Carolina mantid, which is more often green than tan, has shorter wings that rarely reach the tail as in the previously described species. Identifying mantids of smaller sizes can be very difficult because of the varied nymph stages of the different species.
(ZooGoer 26(5) 1997. Copyright 1997 Friends of the National Zoo. All rights reserved.)
