What part of a Venus flytrap snaps shut when triggered?

The part of a Venus flytrap that snaps shut when triggered is the trap. More precisely, the trap is formed by two terminal leaf lobes hinged along a central midrib.

The inner surfaces of these lobes contain sensitive trigger hairs. A single touch usually is not enough: the plant generally requires two stimulations within about 20 seconds, helping it avoid wasting energy on raindrops, dust, or other harmless debris. Once triggered, the lobes can close in roughly a tenth of a second.

The trap is actually a highly modified part of the leaf, not a separate mouth or jaw. Its edges have stiff cilia that interlock when it closes, while glands on the inner surface release digestive fluids if the prey continues moving.

The flower, roots, and stem perform different jobs. Flowers produce seeds, roots anchor the plant and absorb water, and the short underground stem supports the leaf rosette. The prey-catching structure is specifically the leaf’s hinged trap.