Carnivorous Plants May Lure Insects With Specially Tailored Scents

Carnivorous pitcher plants seem like something straight out of a science fiction novel: They lure curious insects to their petal-like leaves, and once the bugs fall inside their long, narrow cavity, the plants trap them in a sticky digestive liquid that’s impossible to escape.

But these voracious plants are very real—and scientists are trying to work out how they draw prey into their death traps. One specific subset, known collectively as Sarracenia and found primarily in the bogs of the southeastern United States, eats everything from bees and moths to ants and flies. But botanists have never been able to pinpoint exactly how the Sarracenia plants attract bugs in the first place—or whether they target specific types of prey. Scientists have put forward numerous hypotheses: Maybe the size of the pitcher or the color of the leaves attracts their next meal. Or, perhaps the plants’ scents or nectar glands are impossible for insects to resist.

Now, researchers suggest pitcher plants emit various deadly concoctions of odors to attract different kinds of prey. They shared their findings in a new paper published last week in the journal Plos One.

To understand the role of scent in attracting prey, the team took samples of chemicals called volatile organic compounds, or VOCs, produced by 16 laboratory-grown trumpet pitcher plants representing four different species. Different blends of VOCs can produce different odors.

Next, they compared those odor formulas with the types of insects they found in each plant’s pitchers. They found a link between the scent cocktail a plant produced and the kind of bugs it was digesting. For instance, plants that produced monoterpenes and benzenoids—which are compounds emitted by flowers and fruits—attracted more pollinators, like bees and moths. Plants that emitted fatty acid chemicals, meanwhile, lured more ants.

The findings suggest that carnivorous plants “are not simple passive plants with random captures, and that they can target their prey,” as study co-author Laurence Gaume, a botanist at the French National Center for Scientific Research and the University of Montpellier, tells CNN’s Kate Golembiewski.

The trends revealed in the study are correlations only—researchers did not prove a causal link between odors and bugs. But the findings are a good starting point for understanding more about the unusual lives of carnivorous plants.

“These plants are somehow clued in to say, ‘OK, time to smell good, time to get something in there,’” says Jonathan Gershenzon, who directs the Max Planck Institute for Chemical Ecology and was not involved in the study, to New Scientist’s Sofia Quaglia.

In the future, the researchers hope to conduct more experiments, such as seeing how live insects react to the different odor formulas emitted by the plants. They also want to sample odors produced by pitcher plants growing in their native habitats in the wild. With more data, the research may someday prove useful for real-life applications, such as controlling pests with different odors.

For now, though, the role of scent remains largely a mystery.

“Of the signals involved in communication, odor is probably the most cryptic to humans,” says Gaume to the Natural History Museum in London’s James Ashworth.

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Sarah Kuta is a writer and editor based in Longmont, Colorado. She covers history, science, travel, food and beverage, sustainability, economics and other topics.