The life span of adult head lice living on a human head is about 30 days. This follows seven days as a nymph after hatching. If a louse is starved of blood meals, it dies in one to twp days, according to the Centers for Disease Control and Prevention.
The life cycle of a head louse has three stages, states the CDC. Head lice eggs are called nits. Nits are less than 1-millimeter long, they are difficult to see and they hatch in about one week. Nymphs are released from the nits and appear as miniature adult lice, roughly pinhead sized. After seven days and three molts, the nymphs are adult lice the size of sesame seeds. The larger female louse can lay up to eight nits per day.