Photo courtesy Peter D'Amato A Venus Flytrap from California Carnivores

You're reading the table of contents of your new science book and there it is in black and white: carnivorous plants. Thoughts race through your mind, "Seriously, carnivorous plants? Carnivorous means flesh-eating, right? Plants that eat flesh? Do they eat human flesh? Could one eat my dog? This cant' be for real, can it?"

Yes, it can.

Carnivorous plants have existed on this planet for thousands of years. In fact, today there are more than 500 different kinds of these plants. Their appetites range from insects and spiders to small, one- or two-cell aquatic life forms. To be considered carnivorous, a plant must attract, capture, kill and digest insects or other animal life.

One carnivorous plant in particular has captured the public's imagination: The Venus Flytrap (Dionaea muscipula). Although the Venus Flytrap has fascinated people across the world, the plants actually grow in an incredibly small geographic area. In the wild, they are found in a 700-mile region along the coast of North and South Carolina. Within this area, the plants grow in humid, wet and sunny bogs and wetland areas.

Photo courtesy U.S. Geological Survey

OK, don't get carried away thinking you'll avoid any outdoor activity while visiting the Carolinas because you or your dog could be on the menu. Here are some of the Venus Flytrap's mealtime favorites: spiders, flies, caterpillars, crickets and slugs. See, humans and canines are not on the list. Now we know what they eat, but let's see why they eat it.

Most plants thrive on gases in the air plus water from the soil. During a process called photosynthesis, plants use the energy of the sun to convert carbon dioxide and water to sugar and oxygen. The sugar produced is then converted to energy. In addition to using sugar to get energy, plants need to make amino acids, vitamins and other stuff to survive. To accomplish this, plants require additional nutrients like nitrogen, phosphorus, magnesium, sulfur, calcium and potassium. These additional nutrients are usually found in the surrounding soil.

While Venus Flytraps do get some of their energy like other plants do, through the process of photosynthesis, they aren't able to get the additional nutrients they need from their surroundings. In the bogs where Venus Flytraps live, the soil is acidic, and minerals and other nutrients are scarce. Most plants can't survive in this environment. But the Venus Flytrap has developed the ability to thrive in this unique ecological niche. It has an another way of getting key nutrients like nitrogen. It eats living creatures. Living creatures like insects provide a good source of the nutrients missing from the soil.

Human vs. Flytrap While our imaginations dream up huge killer plants, we're the real threat. The Venus Flytrap has been endangered in the wild due to: over-collection by Flytrap enthusiasts draining and destruction of the natural wetlands where they grow pollution Because of this, there is a hefty fine in the Carolinas for taking Venus Flytraps from their native habitats. But that doesn't mean you can't have one. You can legally buy Venus Flytraps from a number of nurseries.

We now know the "what" and "why" - but how do they do it? Come on, plants don't have eyes, hands, legs or even stomachs for that matter. They can't walk over to the local "Buzzer Queen" and order a caterpillar and fly sandwich with a side of spider legs. So how do they capture and digest their prey? It all centers on a specialized set of leaves that act as both mouth and stomach in one.

First, the Venus Flytrap's leaves form a trap. The leaves secrete a sweet nectar that attracts insects searching for food. When an insect lands or crawls on the trap, it is likely to run into one of six, short, stiff hairs on the trap's surface. These are called trigger hairs, and they serve as a primitive motion detector for the plant. If two of these hairs are brushed in close succession, or one hair is touched twice, the leaves close down upon the unsuspecting insect within half a second. The insect caught inside the partially closed trap will continue to thrash about, trying to escape. At least one (if not all) of the trigger hairs will be tweaked by the insect's movement. This serves as the signal to close the trap entirely.

Inanimate objects like twigs and leaves that fall into the trap, or objects that are placed there - like a pencil (you know you'd try it, too), will not move around and fire the trigger hairs. So the trap stays in its partially shut state until tension can be re-established in the leaves of the trap. This process takes about 12 hours, at which point the leaves spread apart again. The unwanted object either falls out as the leaves re-open or it's blown out by the wind.

Photo courtesy David Webb and The Botanical Society of America An insect crawling on the jaw-like leaves of the Venus Flytrap

Let's say the Venus Flytrap has trapped a small, juicy caterpillar. It has struggled enough so that the trap is now fully closed. What happens next? The edges of the Venus Flytrap's leaves have finger-like cilia that lace together when the leaves press shut. These long, hair-like projections make the plant look like it has spiny teeth; but the cilia are really only used to latch the trap shut. Once shut, the leaves form an airtight seal. This keeps digestive fluids and insect parts inside the trap and bacteria and molds outside the trap. It's good to keep bacteria and mold out because if allowed to grow within the trap, not only will it decompose the rotting insect inside, it will also attack the plant.

Insect, check. Trap sealed, check. Now it's time for the leaves to change from trap to stomach. Just like our stomach, the trap secretes acidic digestive juices. The insect is bathed in these juices over a period of five to 12 days, during which the insect is digested and nutrients are extracted. The time it takes depends on the size of the insect, the age of the trap and the surrounding temperature. The larger the insect is, the longer it takes to break down. Because digestive fluid is recycled after each digestion, an older trap may secrete a somewhat weaker mix of acid and enzymes. The ambient temperature can affect the rate of decomposition. For example, increasing temperature can speed up the process.

Once the nutrients are depleted from the acidic bath, the plant reabsorbs the digestive fluid. This serves as a signal to reopen the trap. The remains of the insect -- anything that couldn't be digested, like the exoskeleton -- are usually either washed away in the rain or blown away by the wind.

Other Carnivorous Plants Even before reading this article, you had probably already heard of the Venus Flytrap. But what about other carnivorous plants? Read this list to see if you have heard of any of these plants. Albany Pitcher Plant Bladderwort Butterwort Cobra Lily Corkscrew Plant Dewy Pine Monkey Cup Rainbow Plant South African Fly Bush Sundew Waterwheel Plant