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Bugs Beware!
Exploring Carnivorous Plants

Author: Sarah Pounders

Carnivorous plants are a prime example of living organisms adapting to survive in a challenging environment. A special ability to capture and decompose animal life forms and then absorb the nutrients they release allows these plants to thrive where other plants struggle. Most are found in boggy wetlands where acidic conditions, high water content, and low oxygen levels lead to very slow decomposition of organic matter and very low soil nutrient levels.

The most common prey of carnivorous plants are small insects such as gnats, flies, bees, moths, beetles, and ants, though on rare occasions animals as large as frogs and small rodents have been found in their traps! Might carnivorous plants devour humans? Don’t worry, scientists have yet to discover one big enough to accomplish such a feat!

Carnivorous plants use a number of tricks to lure insects. The most common enticements are color, scent, and nectar. Insects arrive with the promise of a tasty meal, never realizing that they’re the ones on the menu. There are many subtle adaptations that result in unique trapping mechanisms; examples of the most common of these methods are listed below.

Snapping Traps – Plant leaves enclose prey when a trigger is activated. Examples include the Venus flytrap (at right) and waterwheel plant.	Dionaea muscipula
Pitfall Traps - Tube-shaped leaves serve as pits of doom for insects. Once they enter, they can’t fly or crawl out, usually because the walls are slippery and covered with downward facing hairs or growths. Insects eventually drown and decompose in a liquid mix at the bottom of the pit. Examples include the many species of pitcher plants (Serracenia) and monkey cups (Nepenthes).	Nepenthes ampullaria
Flypaper Traps - Sticky or gooey surfaces entangle insects. Examples include sundews (Drosera) and butterworts (Pinguicula).	Drosera spatulata
Suction Traps - A trap door mechanism springs open when triggered and sucks the insect into a sac-shaped structure, then closes behind it. The bladderwort (Utricularia) at right is an example.	Utricularia macrorhiza

(For more detailed descriptions of each of these trapping techniques, check out Carnivorous Plant FAQ courtesy of the International Carnivorous Plant Society. You'll find basic animation of traps in action by visiting here.)

Once insects are trapped, plants release enzymes to start the decomposition process. “Digestion” of the insects may also occur through symbiotic relationships with other organisms, such as bacteria. Interestingly enough, other insects may also help with the prey’s demise: Some are immune to carnivorous plant traps and actually scavenge a plant’s surface for those who have been trapped. As these opportunists eat the smorgasbord laid out by the carnivorous plant they leave behind their droppings, which the plant also breaks down for its nutrients!

There are approximately 650 different species of carnivorous plants worldwide, found in every state in the United States and on every continent except Antarctica. In general they grow slowly and are very particular about their growing conditions: full sun, plenty of water, high humidity, and warm temperatures. Attempting to grow carnivorous plants outside of their native environment is tricky, though with care and experience you can succeed. If you want to try them in your classroom, don’t be disappointed if they don’t survive - even experts have lost a few during the learning process. A nearby botanical garden or nature preserve may have a collection you can view instead.

Despite their broad distribution across the globe, carnivorous plants are in danger of becoming extinct for a number of reasons.

Habitat loss. Wetlands are being lost to land development for housing and farming. Since carnivorous plants aren't easily transplanted to new environments, when their natural habitat is gone, their wild populations will also disappear. Carnivorous plants have the advantage in poor soils, but in areas with normal soil conditions, non-carnivorous plants (both native and invasive species) will out compete carnivorous ones for space and resources.

Collection of wild populations. Even though carnivorous plants are hard to grow and rarely survive long for any but the most experienced gardener, some individual and professional growers obtain their stock from the wild, despite laws and regulations limiting and in some cases prohibiting collection.

Pollution of habitats. In addition to loss of bogs and wetland habitat, pollution of the land and water by pesticides and fertilizers also has a hand in reducing populations.

Protecting these unique plant species is vital to maintaining biodiversity in the plant kingdom. What’s Up with Wetlands? introduces students to current events related to carnivorous plant populations and challenges their critical reading skills. Create a Carnivorous Plant challenges them to ponder the relationship between prey and predator by designing their own unique carnivorous plants.

For more background information to support your classroom explorations, visit:

Peter's Savage Garden (Exploratorium's Science of Gardening Videos)

Carnivorous Plant Pages (Botanical Society of America)

Carnivorous Plant FAQ (Sarracenia.com, on behalf of the International Carnivorous Plant Society)

International Carnivorous Plant Society

California Carnivores

Wondrous Wetlands

All images above are © sarracenia.com. Used by permission.