The Venus Flytrap's Lethal Allure | Science | Smithsonian
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One of only two plants worldwide that actively trap animal prey, the flytrap is at home in a surprisingly small patch of U.S. soil. (Lynda Richardson)

The Venus Flytrap's Lethal Allure

Native only to the Carolinas, the carnivorous plant that draws unwitting insects to its spiky maw now faces dangers of its own

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As I slogged through black swamp water, the mud made obscene smooching noises each time I wrenched a foot free. “Be careful where you put your hands,” said James Luken, walking just ahead of me. “This is South Carolina”—home to multitudinous vipers, canoe-length alligators and spiders with legs as thick as pipe cleaners. Now and then Luken slowed his pace to share an unnerving navigational tip. “Floating sphagnum moss means the bottom is solid—usually.” “Copperheads like the base of trees.” “Now that is true water moccasin habitat.”

Our destination, not far from the headwaters of the Socastee Swamp, was a cellphone tower on higher ground. Luken had spotted a healthy patch of Venus flytraps there on an earlier expedition. To reach them, we were following a power-line corridor that cut through oval-shaped bogs called Carolina bays. Occasionally Luken squinted at a mossy spot of earth and declared that it looked “flytrappy.” We saw other carnivorous species—lippy green pitcher plants and pinkish sundews no bigger than spitballs—but there was no sign of Dionaea muscipula.

“This is why they call them rare plants,” Luken called over his shoulder. “You can walk and walk and walk and walk and not see a thing.”

Luken, a botanist at Coastal Carolina University, is one of the few scientists to study flytraps in the wild, and I was starting to understand why he had so little competition.

A shadow of a vulture glided over us and the sun glowered down. To pass the time Luken told me about a group of elementary-school teachers he’d recently led into a salt marsh: one had sunk nearly up to her neck in mud. “I really thought we might lose her,” he said, chuckling.

As we neared the cellphone tower, even Luken began to look a little discouraged. Here the loblolly and longleaf pines were shriveled and singed-looking; wildfires that had roared through the Myrtle Beach region apparently reached the area. I sipped at the last of my water as he scouted for surviving flytraps in the margins of a newly dug fire line.

“Give me your hand,” he said suddenly. I did, and he shook it hard. “Congratulations. You’re about to see your first flytrap.”

Venus flytraps’ considerable eccentricities have confined them to a 100-mile-long sliver of habitat: the wet pine savannas of northern South Carolina and southern North Carolina. They grow only on the edges of Carolina bays and in a few other coastal wetland ecosystems where sandy, nutrient-poor soil abruptly changes from wet to dry and there’s plenty of sunlight. Fewer than 150,000 plants live in the wild in roughly 100 known sites, according to the North Carolina Department of Environment and Natural Resources.

Instead of absorbing nitrogen and other nutrients through their roots, as most plants do, the 630 or so species of carnivorous plants consume insects and, in the case of certain Southeast Asian pitcher plants of toilet-bowl-like proportions, bigger animals such as frogs, lizards and “the very, very occasional rodent,” says Barry Rice, a carnivorous plant researcher affiliated with the University of California at Davis. The carnivores are particularly abundant in Malaysia and Australia, but they’ve also colonized every state in this country: the Pine Barrens of coastal New Jersey are a hot spot, along with several pockets in the Southeast. Most varieties catch their prey with primitive devices like pitfalls and sticky surfaces. Only two—the Venus flytrap and the European waterwheel, Aldrovanda vesiculosa—have snap traps with hinged leaves that snag insects. They evolved from simpler carnivorous plants about 65 million years ago; the snap mechanism enables them to catch larger prey relative to their body size. The fossil record suggests their ancestors were much more widespread, especially in Europe.

Flytraps are improbably elaborate. Each yawning maw is a single curved leaf; the hinge in the middle is a thick vein, a modification of the vein that runs up the center of a standard leaf. Several tiny trigger hairs stand on the leaf’s surface. Lured by the plants’ sweet-smelling nectar glands, insects touch the trigger hairs and trip the trap. (A hair must be touched at least twice in rapid succession; thus the plant distinguishes between the brush of a scrambling beetle and the plop of a raindrop.) The force that closes the trap comes from an abrupt release of pressure in certain leaf cells, prompted by the hair trigger; that causes the leaf, which had curved outward, to flip inward, like an inside-out soft contact lens snapping back into its rightful shape. The whole process takes about a tenth of a second, faster than the blink of an eye. After capturing its prey, a flytrap excretes digestive enzymes not unlike our own and absorbs the liquefying meal. The leaf may reopen for a second or even a third helping before withering and falling off.

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About Abigail Tucker

A frequent contributor to Smithsonian, Abigail Tucker is writing a book about the house cat.

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