A Wily Trap, Even for a Pitcher Plant Pitcher plants are carnivores that rely on insects for nourishment. One species of the plant, found in Southeast Asia, uses raindrops to trap prey in its fluid-filled pitcher, a new study reports. Writing in the journal PLoS One, researchers describe how the species Nepenthes gracilis has a springboardlike mechanism built into its lid. Insects seek shelter from rain on the underside of the plant's lid. Then, when raindrops hit the top of the lid, the insects are flung into the pitcher, said Ulrike Bauer, a biologist at the University of Cambridge in England and the study's first author. Dr. Bauer and her colleagues set up a pitcher plant in a laboratory, with a drip system hanging above that simulated raindrops. In a box nearby, the researchers kept a colony of ants that were naturally attracted to the plant's nectar. The underside of the pitcher plant's lid is covered with specialized wax crystals, Dr. Bauer said. This surface seems to allow enough grip for the insects to walk on the surface to seek shelter and feed on nectar when the weather is calm. But it is also slippery enough that when it rains, insects are thrust from the lid into the clutches of the pitcher. This mechanism may let the pitcher plant capture a wider variety of insects than other types of pitcher plants. "Flying insects with very delicate wings, like flies and bees and wasps, may seek shelter from the rain," Dr. Bauer said.