Raindrops help pitcher plants trap dinner

The lower lid of the pitcher plant Nepenthes gracilis secretes nectar that attracts unsuspecting insects. In the rain, the lid becomes a spring-loaded death trap.

Ulrike Bauer/Univ. of Bristol

By Sarah Schwartz

October 5, 2015 at 3:00 pm

Ants crawling on the underside of a pitcher plant are flicked to their death when raindrops hit the lid. Ulrike Bauer/Univ. of Bristol

The pitcher plant Nepenthes gracilis gets a little help from raindrops in snagging a meal. When falling rain strikes the lid that hangs over N. gracilis ’ fluid-filled trap, the lid acts like a spring-loaded plate, flinging insects crawling on its underside to their death .

N. gracilis, which is native to Asia, is specially equipped to trap its prey this way. Its lid is lined with slippery wax crystals and vibrates much more quickly than that of a related species of pitcher plant. Both features seem to be crucial to the plant’s prey-trapping strategy. When the researchers removed the slippery wax or attached a slick N. gracilis lid beneath that of another species of pitcher plant, few to no ants fell to their death during simulated rainfall, researchers report October 5 in the Proceedings of the National Academy of Sciences.