The inner surface of a Venus flytrap has a few spiky hairs, and when an insect or spider is crawling along the leaves and contacts more than one of those hairs in a period of 20 seconds or less, the trap shuts closed. This mechanism serves as a safeguard against wasting energy by trapping objects with no nutritional value, and the plant will only begin digestion after five more stimuli to ensure it has caught a live bug worthy of consumption.