The Snap of the Venus Flytrap
Most plants are happy to sit still and drink in sunlight, but the Venus flytrap has a surprising trick. It catches and eats insects. In nature it grows only in a small part of the southeastern United States, in wet, boggy ground.
Bog soil is poor in some of the nutrients that plants need, especially nitrogen. Plants that grow there must find another way to get what the soil lacks. The flytrap solves the problem with its leaves. The end of each leaf is shaped like a pair of jaws with stiff little bristles along the edges.
Inside each trap are tiny trigger hairs. When an insect walks in and touches a hair once, nothing happens. If it brushes a hair a second time within a short while, the trap snaps shut. This double check keeps the plant from wasting energy on a raindrop or a bit of falling dust.
The bristles lock together like fingers, making a cage. Then the plant gives off juices that slowly break down the soft parts of the insect. After several days, the trap opens again and the leftover shell blows away.
A flytrap still makes food with sunlight like other green plants. The insects are more like a vitamin that helps it grow in difficult ground.