Steering Clear of Entrapment

The green sweat bee, Augochlorella gratiosa, is an important Venus flytrap pollinator.

Elsa Youngsteadt

The carnivorous Venus flytrap, Dionaea muscipula, uses its specialized leaves as snap traps to feed upon arthropods. But, as a flowering plant, it also relies on invertebrates for pollination. A new study provides the first catalog of flytrap flower visitors and examines whether these potential pollinators should worry about becoming prey.

Researchers led by entomologist Elsa Youngsteadt at North Carolina State University spent four days collecting flower visitors and trapping prey from thousands of wild Venus flytraps in coastal North Carolina. For the 426 flower visitors, the researchers recorded which animals picked up pollen, how much pollen they carried, and how much of it was flytrap pollen. They also collected 212 prey animals, primarily spiders and insects, from the plants’ closed traps.

The 238 flower visitors carrying flytrap pollen included bees, beetles, spiders, butterflies, flies, and other insects. The most important of these, based on abundance and pollen load, was a sweat bee, Augochlorella gratiosa. The researchers recorded forty-nine individuals of this species, 82 percent of which carried flytrap pollen. On average, over 90 percent of the pollen they carried was flytrap pollen, indicating high flytrap “fidelity”—the bees were most likely not visiting many other types of flowers. Other abundant flytrap pollen carriers included the longhorn beetle (Typocerus sinuatus) and the checkered beetle (Trichodes apivorus). The researchers next hope to measure how efficient different flower visitors are at distributing pollen among flytraps, to determine which one is the most important pollinator.

Only thirteen of the ninety-eight flytrap flower-visiting taxa—and none of the ten most abundant, except a single crab spider—were also found in traps. Future research will explore the mechanism for this separation between pollinators and prey. The researchers suspect this is due to the height of the flowers, which mainly attract flying insects, while the lower traps mainly catch crawling animals. 87 percent of flower visitors in this study could fly, compared to only 20 percent of the trapped animals. The traps and flowers may also have different visual and chemical cues, which allow them to attract different species.

Future work to better understand the ecology and environmental needs of Venus flytraps could inform conservation measures to protect this unique plant, which is currently listed as Vulnerable by the International Union for Conservation of Nature. (The American Naturalist)