Pets can be a carrier for the lice but the lice cannot survive long on an animal. Reproduction. Females lay up to 400 eggs in their lifespan, which is spaced out to about eight eggs per day. These eggs hatch in one to two weeks. Life Cycle. Head lice begin as empty eggs called nits. They attach themselves near the root of the hair with a substance that is like glue and cannot be simply washed away. When the eggs hatch, the nymphs feed on blood from the scalp. Life Span. Nits, or lice eggs, can live for up to 10 days but will need to feed on human blood after hatching. Adult lice can live for up to one month on the head of a human but die within two to three days without body contact. The total life span of lice is 40 to 50 days, if you include the complete life cycle: egg, nymph and adult. Fun Fact