The Venus' flytrap will only clamp its leaves shut if prey trips its trigger hairs two times within about 20 seconds. If only one hair is touched, or the touches occur minutes apart, the leaf trap does not close. This remarkable evolutionary strategy avoids wasting energy by false alarms, such as rain drops and debris.

Rapid leaf closure involves an electrical mechanism similar to animal action potentials. Touching a trigger hair opens ion channels and generates an electrical signal. Two touches within roughly 20 seconds produce two action potentials triggering a rapid release of ions and water loss, thus collapsing cell turgor pressure. The leaf shape flips rapidly from convex (open) to concave (closed) in roughly 0.1 to 0.3 seconds. The precise molecular mechanism is very complex & beyond the scope of this lecture.

A Venus' flytrap leaf typically has six trigger hairs on each leaf; arranged as three hairs on each folded (opposing) surface in a triangular pattern. The leaf margins have interlocking spines to trap prey.