How Does the Venus Flytrap Trap Insects?
Some plants eat insects. One such insect-eating plant is the Venus flytrap. Its traps are special leaves. Hinges let the halves of each leaf snap together. On each leaf are tiny trigger hairs. When a fly steps into the open trap, it brushes against the trigger hairs.
SNAP! The halves spring shut, trapping the victim inside. Once sprung, the leaf acts as a stomach digesting the prey. Later, the trap opens to await another victim. Venus flytraps grow in wet places, where the soil lacks usable nitrogen. The plant gets this food from the insects it traps.
To attract flies or other prey, the Venus flytrap secretes nectar on to its open traps. Insects smell the sweet nectar and once they land on the leaves, they trip the trigger hairs on the outside of the traps. This causes the cells in the leaves to expand. In less than a second, the leaves shut.
At first, the traps do not close tightly so that small insects can escape. When larger insects begin to struggle, cilia within the leaves tighten over the prey, and the leaves clamp tightly over the plant’s meal. Insect secretions, like uric acid, will also cause the trap leaves to close more tightly. Within a few minutes, the traps form airtight seals and begin the digestion process.
Since the Venus flytrap lacks a nervous system or muscles, it is still a mystery as to what causes the trapping mechanism. One possibility is that the leaves move via fluid pressure. The plant’s electrical currents that travel through its phloem, or plant tissue, activate this special fluid pressure that allows the leaves to clamp shut.
If the traps shut over something that is not food, like a pebble, the leaves will reopen in roughly 12 hours to discard the object. The plant has digestive glands that line the inside of the trap leaves. When insects are trapped, the digestive glands secrete fluids with enzymes that break down the insides of the insect, kill harmful bacteria and remove nutrients.
In five to 12 days, the trap reopens and discards the insect’s exoskeleton. Each trap will only digest three to five meals spending several months dormant while the plant photosynthesizes, and then fall off. The plant will grow new leaves to replace the traps that die off.