The Venus flytrap is the rock star of the plant world. Each green jaw is lined with tiny stiff trigger hairs. When an insect crawls across them and bumps two hairs (or the same hair twice) within about 20 seconds, the trap snaps shut in roughly a tenth of a second - too fast for a fly to escape.
That double-touch rule is actually the plant counting. Botanists have shown the flytrap holds a kind of electrical memory of the first touch for about 20 seconds. If a second touch arrives in time, fire! If not, the count resets. That keeps the plant from wasting energy on raindrops or falling leaves.
Once shut, the trap squeezes tighter as the prey wriggles. After a few more touches it seals fully and starts dissolving the bug in digestive juice over about a week. The same trap can only catch and reopen three or four times before it dies and the plant grows a new one.
