Ever wondered about meat-eating plants?

Plants and animals usually have different ways of feeding themselves. Within the animal kingdom, herbivores eat plants, carnivores eat mostly herbivores, and omnivores eat both. (Even though your little brother might refuse to eat anything green, he still qualifies as an omnivore.) When animals die, their bodies decompose (break down) and return nutrients to the soil that help plants grow.

Most plants don’t eat anything. Instead, they use light from the sun to convert water and carbon dioxide into a sugar that helps them grow. (This process is called photosynthesis.) They also absorb nutrients such as nitrogen and phosphorous from the soil.

Animals have the ability to move around to feed themselves. Plants don't. If a plant is growing in a nutrient-poor environment, it must adapt to survive. Carnivorous plants are rare, but 600 species have been identified throughout the world.

The first time I learned about carnivorous plants was in third grade. My teacher introduced her class of budding botanists to the Venus’ flytrap. We watched a short movie and were amazed to learn that these plants ate flies.

Carnivorous plants eat mostly insects, but one-celled organisms, spiders, beetles, crustaceans and occasionally small frogs, lizards and mice are also on the menu.

One way of categorizing carnivorous plants is by describing how they catch their prey. Their traps vary in size, shape and function, but they are basically specialized leaves.

Snap traps. Venus' flytraps and waterwheel plants have leaves that are hinged in the middle, so they can close like a book. The leaves snap shut when trigger hairs are touched. The leaves of Venus' flytraps have spines on the ends that look like the bars of a jail cell when closed and serve the same purpose.

Flypaper traps. The leaves of sundews and butterworts are dotted with glands that produce a sticky substance. In some species, the leaves are passive, which means the insect is simply trapped by the plant's secretions. In others, the leaves curl up like a fist to help capture prey after sensing its presence.

Suction traps. Bladderworts are aquatic plants that have leaves shaped like bladders (pouches) with a vacuum inside. One end is covered with a "door." When something touches the trigger hairs on the door, it opens, and the vacuum sucks the prey into the trap.

Pitfall traps. The leaves of pitcher plants have evolved into tubelike structures filled with water and digestive enzymes. The top of the trap often has a covering that looks a little like a raised toilet seat. Its function is to keep the trap from overflowing with rainwater. Once an insect falls into the trap, it's unable to free itself and it drowns.

Lobster-pot traps. Like traps used to catch lobsters, these have one-way entries. The trap of corkscrew plants consists of a Y-shaped leaf. Tiny one-celled organisms find their way into the leaf, but hairs that point inward prevent the prey from escaping.

After carnivorous plants catch their meal, they obtain the nutrients they need in one of two ways. Some plants produce chemicals that digest the prey. Some harbor other organisms, such as bacteria, that lend a hand. After their “partners” digest the animal, the plant can absorb the nutrients for its own use.

So the next time your mom or dad asks you to eat some vegetables, be glad the vegetables don’t want to eat you!

Bennett is a Washington pediatrician. His Web site, www.howardjbennett.com, includes past KidsPost articles and other cool stuff.

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