Picky eaters: Venus flytraps only chow down on certain insects, study finds

RALEIGH, N. C. — Venus flytraps are the stuff of horror movies. Insects that help pollinate these carnivorous plants, however, can relax. A new study finds Venus flytraps are actually picky eaters, in a sense, only opting to close their colorful jaws on bugs that aren’t pollinators.

Out of hundreds of carnivorous plants, Venus flytraps have their own unique genus and location, all existing within a 100-mile radius of Wilmington, North Carolina. Researchers at North Carolina State University sought to learn more about the insects that pollinate them, and in the process learned that the snapping jaws have an uncanny ability to detect which insects are friends or foes. The pollinators are allowed to go free while the plant dines off the alternative menu.

Flower beetle on a Venus flytrap.
Flower beetle on a Venus flytrap. (Photo credit Clyde Sorenson / North Carolina State University)

“Everybody’s heard of Venus flytraps, but nobody knew what pollinated them–so we decided to find out,” says Clyde Sorenson, coauthor of the study and a professor of Entomology with the university, in a release.

The researchers studied 100 insects found on flowers during the Venus flytrap’s five-week flowering season. They identified each insect and looked to see which ones were toting pollen and how much. Just a few insects — a green sweat bee, a checkered beetle and a notch-tipped flower longhorn beetle — were prevalent and packing a lot of pollen.

Of the prey they retrieved from more than 200 Venus flytraps, researchers say they never found a case where one of the three major pollinator species were made into a meal, despite the fact that the pollinators were repeatedly flirting with the jaws of death.

“One potential reason for this is the architecture of the plants themselves,” according to lead author Elsa Youngsteadt, a research associate with the university. “Venus flytrap flowers are elevated on stems that stand fairly high above the snap traps of the plant, and we found that 87 percent of the flower-visiting individuals we captured–including all three of the most important species–could fly. But only 20 percent of the prey could fly. The pollinator species may simply be staying above the danger zone as they go from flower to flower, making them less likely to be eaten.”

Checkered beetle on a Venus flytrap blossom.
Checkered beetle on a Venus flytrap blossom. (Photo credit: Elsa Youngsteadt / NC State University)

Researchers say there is still a lot to learn about the Venus flytrap. “We know that the snap traps are different colors than the flowers, and may possibly lure different species,” Sorenson says. “We don’t yet know if they release different scents or other chemical signals that may also differentiate which portions of the plant are attractive to pollinators versus prey. That’s one of the questions we plan to address moving forward.”

In addition, the authors would like to study other sites within the plant’s native range to find out whether the same pollinators are just as important in all locations. They would like to find out how much pollen is required and how much nectar is produced as a result. Another burning question: why do periodic fires in their native habitat help the Venus flytrap to thrive?

“These findings answer basic questions about the ecology of Venus flytraps, which is important for understanding how to preserve a plant that is native to such a small, threatened ecosystem,” says Youngsteadt. “It also illustrates the fascinating suite of traits that help this plant interact with insects as both pollinators and prey.”

A plant that can choose from a menu and grow a stomach sure earns its place alongside Little Shop of Horrors, particularly if you are a fly.

The study’s results were published in the April 2018 edition of the journal American Naturalist.