The teeth of a Venus flytrap create a 'horrid prison' for its prey

March 31, 2019, 8:43 a.m.
Venus flytrap with trapped fly
Photo: Kuttelvaserova Stuchelova/Shutterstock

When an unsuspecting insect lands on the leaf of a Venus flytrap, it trips tiny trigger hairs on the surface of the plant's lure. To ensure the plant has truly encountered prey, and not a raindrop or some other useless substance it can't eat, the trigger hairs must be tripped twice within 20 seconds, reports the San Diego Zoo. Then — wham! — the "jaws" of the plant snap shut in less than a second, trapping dinner.

The plant's hinged traps are edged with small, teeth-like bristles that can make a significant difference in whether prey stays confined. Testing one of Charles Darwin's original hypotheses about the flytrap, researchers in a new study found the spikes play a key role in preventing medium-sized prey from escaping.

"We provide the first direct test of how prey capture performance is affected by the presence of marginal spikes, trichomes that provide a novel function in Venus flytraps by forming what Darwin described as a 'horrid prison,'" writes lead author Alexander L. Davis, a Ph.D. student in the department of biology at Duke University, in a statement.

For the study, which was published in The American Naturalist, researchers set up 34 Venus flytraps in a laboratory with "on-ramps" offering easy access for crickets to reach the plants. They removed the teeth in half of the plants and recorded what transpired. The researchers then performed a similar experiment with 22 flytraps in a botanical garden.

In the lab setting, flytraps with teeth caught 16.5 percent of insects, while their toothless counterparts only trapped 5.8 percent. Similarly, plants in the botanical garden had a success rate of 13.3 percent when they had their spikes, but only 9.2 percent if their spikes had been removed.

Interestingly, teeth seemed to offer the most assistance in keeping medium-sized prey trapped. Davis speculates that larger insects could use the spikes as leverage to pry themselves free, wiggling out of the flytrap before they could be eaten.