Carnivorous plant discovery validates theory proposed by Darwin 150 years ago

In his 1875 book Insectivorous Plants, Darwin studied two European species from the same family and noticed their sticky hairs could catch insects. He suggested that some species in the group might actually feed on their prey. However, the analytical tools of his era were not advanced enough to test his theory, leaving the question unanswered for nearly 150 years.

The discovery began during fieldwork in Shangri-La, Yunnan province, when researchers noticed Saxifraga candelabrum's sticky hairs were packed with bugs — averaging 71 insects per plant.

To prove that insect trapping was a permanent evolutionary trait rather than an accidental event, the team surveyed 45 historical plant samples collected between 1888 and 2016. A total of 43 of them still had insects stuck to their hairs, proving the plant has been preying on insects for well over a century.

Scientists also discovered that the plant uses floral scents to lure insects. However, its sticky traps mostly catch midges — small flies that do little to help fertilize the plant. Larger and more effective pollinators, such as hoverflies and wild bees, rarely get stuck. This smart tactic allows the plant to hunt for food without accidentally killing the insects it relies on to reproduce.

Many plants use sticky hairs purely to keep harmful bugs away. To prove Saxifraga candelabrum actually digests its catch for nutrients, researchers tested for digestion-aiding proteins. They found phosphatase — an enzyme that breaks down animal matter — right inside the plant's sticky hairs. They then used chemical tracking with nitrogen isotopes (special elemental markers) to confirm that the plant absorbs nitrogen from the digested bugs to fuel its flowering and fruit growth.