Pitcher Plants Turn Their Trap On and Off

The carnivorous pitcher plant lures insects - mostly ants - to their deaths with the promise of the sweet nectar inside. The insects slide down the slippery surface of the plant's inner rim, where they drown in the liquid in the plant's trap. But a new study, by Dr. Ulrike Bauer from the School of Biological Sciences at the University of Bristol, has found that the pitcher plant has evolved a unique 'on-off' mechanism for maximizing the number of ants the trap can capture. A daily cycle of environmental conditions - including humidity and rain - creates a period of time when the trap is dry. Scout ants, in search of food sources for their colonies, are not trapped, and recruit worker ants to the pitcher plant's nectar. When the many workers find the pitcher plant later in the day, it has returned to being slippery and captures many of them.