Interesting fact about the Venus flytrap. The flytrap closes on its prey when one of the trigger hairs (the little hairs inside the trap) is brushed against by the prey not once, but twice. If the prey brushes up against the same hair twice within approximately 20 seconds of the first and second contact, the trap closes on the prey. Once the trap is closed, if the prey moves and hits the trigger hairs 5 more times, then digestion starts to take place. This is a safeguard the flytrap has developed to keep from wasting energy closing the trap and digesting on either low energy insects or items that cannot be digested (like water, or inanimate things falling into the trap like a leaf or other debris.
Yellow Jackets Being Caught by Venus Flytraps