The Venus Flytrap, Dionaea muscipula, is a carnivorous plant that catches and digests animal prey—mostly insects and arachnids. Its trapping structure is formed by the terminal portion of each of the plant's leaves and is triggered by tiny hairs on their inner surfaces. When an insect or spider crawling along the leaves comes into contact with one or more of the hairs twice in succession, the trap closes. The requirement of redundant triggering in this mechanism serves as a safeguard against the spurious expending of energy toward trapping other, non-living things which may not reward the plant with similar nutrition.

The plant's common name refers to Venus, the Roman goddess of love, whereas the genus name refers to Dione. Dionaea is a monotypic genus closely related to the waterwheel plant and sundews.

The Venus Flytrap is one of a very small group of plants that are capable of rapid movement, such as Mimosa, the Telegraph plant, sundews and bladderworts.

The mechanism by which the trap snaps shut involves a complex interaction between elasticity, turgor and growth. In the open, untripped state, the lobes are convex (bent outwards), but in the closed state, the lobes are concave (forming a cavity). It is the rapid flipping of this bistable state that closes the trap, but the mechanism by which this occurs is still poorly understood. When the trigger hairs are stimulated, an action potential (mostly involving calcium ions — see calcium in biology) is generated, which propagates across the lobes and stimulates cells in the lobes and in the midrib between them. Exactly what this stimulation does is still debated: cells in the outer layers of the lobes and midrib may rapidly secrete protons into their cell walls, loosening them and allowing them to swell rapidly by osmosis and acid growth; alternatively, cells in the inner layers of the lobes and midrib may rapidly secrete other ions, allowing water to follow by osmosis, and the cells to collapse. Both, either or neither of these mechanisms may play a role.

If the prey is unable to escape, it will continue to stimulate the inner surface of the lobes, and this causes a further growth response that forces the edges of the lobes together, eventually sealing the trap hermetically and forming a 'stomach' in which digestion occurs. Digestion is catalysed by enzymes secreted by glands in the lobes. Digestion takes about ten days, after which the prey is reduced to a husk of chitin. The trap then reopens, and is ready for reuse, even though the trap rarely catches more than three insects in its lifetime.

For More Information: Venus Flytrap: K-12 Experiments & Background Information

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