This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: In the world of carnivorous plants, Venus flytraps—with their showy, snapping reflexes—have long hogged the limelight. But plants have many creative bug-capture strategies, from slippery waxes to vibrating lids to bizarrely textured fluids.
Raffles' pitcher plant (Nepenthes rafflesiana) is one such example. The tropical vine has funnel-shaped leaves called pitchers with enticing nectar on their rims but no delightful drink inside. Instead, they are filled with acidic digestive fluid that stretches when pulled, like a piece of chewing gum.
When flies and ants slip on the leaves' rims, they tumble into a pool of this liquid. But struggle as they might, the bugs can't escape. "It's like quicksand," says Laurence Gaume, an ecologist with the French National Center for Scientific Research and the University of Montpellier.
The faster the insects wriggle, the more the fluid resists, courtesy of long strings of sugars it contains. After years of study, scientists are still learning new things about how Raffles' pitcher plants weaponize this strange fluid. Gaume first noticed the unusual properties of N. rafflesiana's digestive liquid during her fieldwork in the early 2000s, and she wondered if they could explain its bug-catching abilities.
Two features struck her: The pitcher fluid seemed thick and resistant to flow—it had fairly high viscosity, in physics terms. More unusually, when stretched between her fingers, the fluid formed a thin thread, which suggested strong elasticity. To investigate the fluid's properties, she teamed up with physicist Yoël Forterre of the French National Center and Aix-Marseille University in France.
In an article published in 2007, the scientists were the first to describe both the liquid's viscosity and its elasticity. They found that the fluid's elastic force—a property of its long polysaccharide molecules—was 10,000 times greater than its viscosity when insect movements were simulated. In fact, the frantic kicks of an insect lower the liquid's viscosity, making it runnier. (This thinning effect also occurs when liquids like paint and melted chocolate are quickly stirred.) But the fluid's strong elastic force still keeps the insects stuck: When the bugs try to withdraw their limbs from the pool, the liquid pulls back, especially when the insects move quickly.
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