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Let these plants swat the bugs for you

they're widespread and hungry, but they'd only hurt a fly

By Pamela D. Jacobsen / May 1, 2001

Some plants get so hungry they eat flies, spiders, and even small frogs. What's more amazing is that these plants occur naturally (in special environments) in every state. In fact, they're found on every continent except Antarctica.

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You've probably seen a Venus' flytrap. It's often sold in museum gift stores, department stores, and even supermarkets. A small plant, it grows 6 to 8 inches tall in a container. At the end of its numerous elongated stalks are specially modified leaves that act like traps. Inside each trap is a lining of tiny trigger hairs. When an insect lands on them, the trap snaps shut. Over the course of a week or so, the plant dines on its catch.

The Venus' flytrap is just one of more than 500 species of carnivorous (meat-eating) plants, says Barry Meyers-Rice. He's the editor of the International Carnivorous Plant Society's newsletter. Note: Despite any science-fiction stories you might have read, no carnivorous plant poses any danger to humans.

Dr. Meyers-Rice says a plant is carnivorous (or insectivorous, "insect eating"), only if it does all four of the following: "attract, kill, digest, and absorb" some form of prey. Prey includes a number of nectar-loving insects including flies, butterflies, and moths. Carnivorous plants look and act like other green plants - well, most of the time.

All green plants make sugars through a process called photosynthesis. Plants use the sugars to make food and nectar. What makes "meat-eating" plants different is their bug-catching leaves. They need insects for one reason: nitrogen. Nitrogen is a nutrient that they can't obtain any other way. Why?

Almost all green plants on our planet get nitrogen from the soil. Carnivorous plants can't. They live in places where nutrients are hard or almost impossible to extract from the soil because of its acidity. So they've come to rely on getting nitrogen from insects and small animals. In fact, nutrient-rich soil is poisonous to carnivorous plants. Never fertilize them! But don't worry, either, if they never seem to catch any insects. They can survive, but they'll grow very slowly.

Most carnivorous plants live in bogs and wetlands. To be called a bog, an area must have sphagnum moss and water of a specific acidity. Bogs are usually fed by rainwater only. No in-flowing streams or underground springs bring in outside nutrients.

Many carnivorous plants grow alongside streams, or in other areas that are consistently moist. If the ground does dry out, some plant species become dormant - they hibernate, in effect. Or, the parent plant may produce seeds and die. When weather conditions are favorable again, the seeds grow into new plants.

Jerry Hinkley is a biology professor at the College of Lake County in Grayslake, Ill. He takes his science classes on field trips every year to see carnivorous plants. They go to a "quaking bog" just outside Volo, Ill. When someone steps on this sphagnum moss-carpeted bog, each footstep makes the ground bounce up and down, or "quake" slightly.

Hinkley has found small clumps of pitcher plants in Volo Bog. The pitcher plants are a "dazzling thing to see," he says.

Pitcher plants (plant family, Sarraceniaceae) have an exotic urn or pitcher-shaped appearance, hence their name. Instead of traps that snap shut, like the Venus' flytrap, pitcher plants use a passive approach to detain their prey.