The Venus Flytrap Counts Its Victim’s Footsteps

How a panicked insect seals its own fate.

The Venus flytrap is more cunning than you’d think. The famous carnivorous plant can count—namely, how many times potential prey brushes one of its sensory hairs—and things get progressively worse the higher that number goes. The trap of the plant is spotted with stiff hairs that alert the plant to a forthcoming victim, like a fly. Researchers publishing in Current Biology have found that a single touch produces no effect at all, most likely as a preventative measure against false alarms. But a second touch within 20 seconds causes a spike of calcium ions that sends water to its leaves, changing its shape from convex to concave, or, closing the trap… all in a tenth of a second.