A plant has been found turning to carnivory only when it flowers. Triantha occidentalis has flower stalks smothered in small sticky hairs that are a deathtrap for small flies and beetles. Although many other plants have sticky hairs to protect against insects, Triantha actually feeds on the bodies of its victims.
The carnivory was tested by feeding fruit flies with an isotope of nitrogen, a form of the element rarely found in nature. The flies were then put on the sticky hairs and two weeks later the isotope had spread through the plant’s leaves and stems, showing the nutrients in the flies had been absorbed. The sticky droplets on the hairs also had a digestive enzyme found in other carnivorous plants.
Triantha got more than half its nitrogen needs from the flies, much the same as the sticky trap of the carnivorous sundew. And even though its flower stalks are lethal, the flowers of Triantha are pollinated by insects without harming them.
The carnivorous habit of Triantha raises the intriguing possibility of finding other sticky-haired plants that may also be closet carnivores. Perhaps even crop plants such as sticky-haired wild relatives of tomatoes and potatoes.