Close-up photography in this BBC video shows how a Venus flytrap works. We see a fly, tempted by the Venus flytrap's nectar, alight on a trap. As the fly sucks up the tasty bait, it brushes against one of the trap's six hairs. This sets off an internal timer in the flytrap. If a second hair is disturbed within 20 seconds, the trap snaps shut.
Image: YouTube/BBC
