A hungry fly speeds through a forest.It smells nectar（花蜜）and lands on a green leaf.It starts to drink the sweet liquid （液体）.Suddenly， the fly's world turns green.The two sides of the leaf close against each other.Long green teeth lock together around it.The fly has been caught by Venus flytrap.There is no way to run away alive.
The Venus flytrap is perhaps the most famous killer plant.However，scientists have only recently started to understand how it hunts （猎取） and cats.After years of study，plant scientist Alexander Volkov believes he now knows the Venus flytrap's secret. "This，" says Volkov， "is an electrical plant.
There are three small hairs along each of the Venus flytrap's two leaves.When an insect touches a hair，it creates an electrical signal （信号） in the leaf.The insect can continue feeding- for now.But if it touches another hair within 20 seconds，the leaf traps suddenly shut.This allows the plant to tell the difference between a drop of water，for example，and a moving insect.
Once trapped，an insect has little chance of staying alive.Instead of nectar，the Venus flytrap now releases （释放） a different liquid - one that slowly eats away at the insect.Ten days later，almost nothing is left.The plant's leaves open again，and the Venus flytrap is ready for its next meal.
